Macintosh AV General FAQ
		Copyright 1993-95 by James Wang (jwang@csua.berkeley.edu)

		ftp://ftp.csua.berkeley.edu/pub/jwang/
		http://www.csua.berkeley.edu/~jwang/av.html

		Archive:	/pub/jwang/av-faq
		Version:	1.6.0
		Modified:	April 1, 1995

INTRODUCTION
This Frequently Asked Questions list attempts to address the day-to-day needs for users of AV technologies.  The primary audio visual aspects, 16-bit CD-quality stereo sound and analog video in/out, may be already familiar to you.  However, the AV moniker have come to embody a number of other sophistications, some by accident and some by design.  These secondary topics include GeoPort (telephony), PlainTalk (both Speech Recognition and Text-to-Speech), even innovations such as DMA (Direct Memory Access) and SCSI Manager 4.3, for which the first AV models served as a convenient launch pad.

A word about FTP access
For files available via the File Transfer Protocol (FTP), its site and path is indicated in Uniform Resource Locator (URL) format.  URL's are usually pasted into various applications (Anarchie, Fetch, Mosaic) to retrieve the named data.  They are also intuitive enough for hardcore FTP users.
The overwhelming load at sumex-aim.stanford.edu and mac.archive.umich.edu has prompted me to redirect their URL's to the Americal Online mirror site.  You can also pick out a local mirror from the list posted regularly to comp.sys.mac.digest.  Below are some of the FTP and WWW entry points you will find helpful.
ftp://mirrors.aol.com/pub/mac/
ftp://mirrors.aol.com/pub/info-mac/
ftp://ftp.info.apple.com/Apple.Support.Area/Apple.Software.Updates/US/Macintosh/
ftp://ftp.support.apple.com/pub/Apple SW Updates/US/Macintosh/
http://www.info.apple.com/
http://www.support.apple.com/

Note that directories and files at ftp.support.apple.com often contain embedded spaces, for which you must enclose with double quotes when using the standard UNIX ftp client:
> cd "System Software/Other System Software"

TABLE OF CONTENTS

INTRODUCTION	1
TABLE OF CONTENTS	2
HARDWARE	5
Centris / Quadra / Power Macintosh AV feature set	5
AV Technology outreach	5
Model feature overview matrix	6
[AV] Floppy problems	7
[AV] FPU (floating point unit) bombs	7
[AV] Hardware changes	8
[AV] Details on expansion	8
[Power AV] Details on expansion	9
Houdini and Houdini II	9
Clock-chipping an AV or Power Mac	10
Restart and Interrupt	11
Soft power on the 660av and 6100	11
SOFTWARE	12
System software tidbits	12
System software updates	12
Supplemental System software updates	12
[AV] ROM patches	13
Application compatibility	14
Game compatibility	15
[AV] Software that employs the DSP	15
[AV] Developing software for the DSP	15
SCSI Manager 4.3 introduction	16
SCSI Manager 4.3 versions	16
SCSI Manager 4.3 savvy drivers	17
VIDEO INPUT & OUTPUT	18
Graphics and Video independence	18
Graphics: monitors and resolutions supported	18
Graphics: maximum color depth	20
Graphics: switching resolutions on-the-fly	20
Video-in: performance, quality, and limits	20
Video-in: built-in video vs. video cards	21
[AV] Video-in: 1MB frame buffers and more limits	21
Video-in: Video Monitor replacements	22
Video-in: television tuner	22
Video-in: video conference	22
Video-out: starting it up	23
Video-out: flicker reduction	23
Video-out: overscan versus underscan	23
Video-out: video mirroring	24
Video-in, Video-out: subtitling potential	24
Video capture: stock performance	24
Video capture: professional performance	26
Video capture: quality is job #1	26
AUDIO INPUT & OUTPUT	28
Audio-in, Audio-out: hardware specifications	28
Audio-in: line level and the PlainTalk microphone	28
Audio-in: multiple input sources and playthrough	29
Audio-out: sound out rate frequencies	29
Audio capture: performance and quality	29
Audio capture: CD, DAT, and the digital domain	29
Sound editing and manipulation	30
[AV] Professional quality audio mixing software	30
GEOPORT & TELEPHONY	32
GeoPort: what is it?	32
GeoPort Telecom Adapter: know before you buy	32
GeoPort Telecom Adapter: quality control	33
GeoPort Telecom Adapter: software updates	33
Express Modem: initialization strings	33
Express Modem: application compatibility	33
Telephony: where are more tools?	34
PLAINTALK TECHNOLOGIES	35
Terminology and overview	35
Speech Recognition: performance, quality, and limits	36
Speech Recognition: versions and updates	36
Text-to-Speech: synthesizers and requirements	36
Text-to-Speech: versions and updates	37
Text-to-Speech: miscellaneous tidbits	38
MISCELLANEOUS	39
Easter eggs	39
FAQ and file updates	39
MACAV-L mailing list	40

HARDWARE
Centris / Quadra / Power Macintosh AV feature set
The 660av and 840av were introduced on July 29, 1993.  Each shipped with 16-bit CD/DAT-quality stereo sound in/out, one GeoPort, PlainTalk, DMA, SCSI Manager 4.3, NTSC/PAL/SECAM video in, NTSC/PAL video out, all integrated on the motherboard.  The GeoPort,  PlainTalk, and sound features together make up the "audio" half of AV Technologies; all powered by an AT&T DSP3210 co-processor.  The now discontinued 660av and 840av remain the only true multi-processor machines mass-produced by Apple.
The Power Macintosh, introduced on March 14, 1994, all come standard with 16-bit CD-quality stereo sound, two GeoPorts, PlainTalk capability, DMA, and SCSI Manager 4.3.  This time, the "audio" features are driven by the main Power PC processor, and none of the models include a DSP.  The Power AV models adds a PDS options card with a separate frame buffer and the analog video I/O subsystem, bundled along with extras such as the PlainTalk microphone and software.
I've adopted the following conventions for the rest of this document, in both discussion context and in subject heading.  If the relevance of a particular discussion is limited to only one system, the subject line will be appropriately preceded by [AV], or [Power AV], etc.
"AV" by itself refers unambiguously to only the 660av and 840av;
"all AV models" covers the 660av, 840av, and Power Macintosh AV line;
"Power AV" is short for a Power Macintosh fitted with the AV Options card;
"Power Mac" includes any Power Macintosh, AV or regular.

AV Technology outreach
16-bit CD-quality (44.1 kHz) sound:
	The PowerBook 5xx series also supports stereo sound out at these settings, but apparently only mono sound in.
Line-level audio (versus microphone level):
	This has become the standard for all Macs, examples include the LC475/Q605, Power Book 5xx.
Direct Memory Access  (DMA):
	On AV and Power Macs, serial, SCSI, Ethernet, floppy, and audio are all supported with DMA drivers.  Limited DMA also available on the IIfx, Quadra 800, 900 and 950, full DMA also available on Workgroup Servers.
GeoPort:
	Limited to the AV and Power Macintosh.
PlainTalk Speech Recognition (SR):
	Limited to the AV and Power Macintosh.
PlainTalk Text-to-Speech (TTS):
	Can support a Mac Plus running System 6.0.7 and on up.
SCSI Manager 4.3:
	Also supported on most other 68040 systems by System 7.5.
Video input:
	The Macintosh TV can be switched to display television input, but this disables and hides the 68030 completely in the background.  It does not support video in a window, nor video digitization.
	On the other hand, the Quadra 63x series can be added with the Apple TV/Video System, a cable/antenna tuner card in conjunction with a video in-only card (composite and S-video), each in a new specialized and dedicated slot.  The new television features are quite fancy and mature, including named channel setup with password lockout, program reminders, closed captioning, bass/treble control, and an infra-red remote control for the TV, CD-ROM, and computer.
	It's a shame that the TV/Video System is not compatible with the true AV systems.  Also unfortunate is the fact that the 63x does not handle 16-bit CD-quality sound processing, although CD and TV sounds play through cleanly and are mixed with the 8-bit 22 kHz audio from the CPU before output.  Video in a window is handled somewhat differently on the 63x, using an 1MB DRAM-based frame buffer, so the rest of this FAQ may not all apply.
Video output:
	AV and Power AV models can display the desktop on a NTSC/PAL television or projector out of the box.  Other Macintosh models can be fitted with an external encoder box that costs extra.

Model feature overview matrix
                        AV Frame  Best     Memory
Model       CPU Speed   Buffer    Audio    Expansion      Free Slots
-----------------------------------------------------------------------
630         33MHz 040   1MB DRAM  8 bit    1 / 72-pin     1 PDS
                                  22 kHz   80ns, 4-36MB   (030 style)

660av       25MHz 040   1MB VRAM  16 bit   2 / 72-pin     1 PDS, or
(Tempest)   55MHz DSP             48 kHz   70ns, 4-68MB   DAV + 7"NuBus

840av       40MHz 040   1MB or    16 bit   4 / 72-pin     DAV + 3 NuBus
(Cyclone)   66MHz DSP   2MB VRAM  48 kHz   60ns, 0-128MB

6100/60av   60MHz 601   2MB VRAM  16 bit   2 / 72-pin     none left
    /66av                         44 kHz   80ns, 8-72MB

7100/66av   66MHz 601   2MB VRAM  16 bit   4 / 72-pin     DAV + 3 NuBus
    /80av                         44 kHz   80ns, 8-136MB

8100/80av   80MHz 601   2MB VRAM  16 bit   8 / 72-pin     DAV + 3 NuBus
   /100av                         44 kHz   80ns, 8-264MB
   /110av

Memory Expansion notes:
The first line indicates the number of available DRAM SIMM slots, and their type (all are 32-bit wide 72-pin units).  The second line indicates the slowest SIMM speed that should be used, along with minimum and maximum DRAM configurations.  Maximum DRAM size are computed using 32MB SIMM's, replacing factory SIMM's, if any.  The minimum DRAM size indicate the amount of memory soldered on-board.
The 840av may expanded its frame buffer to 2MB via 4 x 256K VRAM SIMM's, rated 80ns or faster.
Quadra DRAM can be expanded one 72-pin SIMM at a time, since each SIMM is 32-bit wide matching the memory bus width.  Power Mac DRAM must be expanded in identical pairs to satisfy the 64-bit memory bus.
Do not use composite SIMM's with any of these machines.  Composite SIMM's are made of many lower density components along with additional support and/or buffer circuitry.  These beasts wreck havoc due to the added electrical load, system noise, and timing overhead.
Brian V. Hughes (hades@coos.dartmouth.edu) adds:
The only SIMMs that are considered 'composite' [with respect to] the 72-pin SIMM specification are 16MB SIMMs that use 32 4M-bit DRAMs rather than 8 16M-bit DRAMs.  8MB SIMMs that use 16 4M-bit DRAMs  are not composite, just like 32MB SIMMs that use 16 16M-bit DRAMs are not composite.

[AV] Floppy problems
The NewAge floppy controller is supposed to write data more precisely than before.  However, 800K floppy reads can fail consistently under certain circumstances, while 800K writes are fine, as are 1.4MB reads and writes.  The official Apple statement blames mass-formatted 800K's whose poor track alignment can no longer be tolerated, some forms of floppy-based copy protection can also render the disk unreadable.  Composite SIMM's have also been directly linked with this problem.
If you have a floppy that refuses to be read, first see if changing the Sound Out rate helps, deactivate Speech Recognition, GeoPort Express Modem, and video-in if necessary.  If there is another Mac nearby, copy the data to a high density disk or use file sharing.  A successful reformat of the disk in question (on the AV) often "fixes" the problem for good.  With CopyDoubler or a similar product, you can turn off floppy verification to avoid read failures when copying in the Finder.
There are also reports of universally slow floppy problems (read, write, and format).  This is likely a manifestation of the faulty ROM disk cache routine, which has been addressed by System Update 3.0 and System 7.5.

[AV] FPU (floating point unit) bombs
Of crashes attributed to the lack of a FPU, Noah Price (noah@apple.com) has one theory:
It can be caused by applications that are not fully 68040 cache compatible.  To test this theory, use the Cache control panel from your Tidbits disk to turn of the 040 cache and see if things improve.
If the 040-cache is not the culprit, open the case cover and make sure the CPU is not labeled as a 68LC040.  Apparently the wrong CPU was used in a very small number of machines, for which a replacement will be provided.  However, the problem can also be caused by bad or poorly seated DRAM, remove or re-seat your SIMM's to check.

[AV] Hardware changes
When Apple dropped the Centris label to avoid market confusion, several models got a CPU speed boost with their Quadra reincarnation.  However, the 660av managed to remain identical immediately before and after the label change.  None of the hardware changes detailed below are related to the name alternation.
The first 660av and 840av models used a SIMM for their 2MB SuperMario ROM's.  Later models surface mounted the ROM chips on the mother board directly.  There are, however, intermediary models with soldered ROM chips and an empty ROM SIMM slot, located in the center of the mother board, orthogonal to the RAM SIMM slots.
For economic and supply considerations, Apple also decided to switch from the original SuperDrive to a less complicated and cheaper manual-inject variety (though still auto-eject).  Late AV's can be distinguished by the recessed floppy face plates.
840AV owner Manoel Felciano (mano@panix.com) also reports that all new CD-ROM equipped systems will ship with the AppleCD 300+, a Matsushita tray-based double-speed mechanism replacing the Sony caddy-based CD 300.  Clinton Bauder (geckO1@applelink.apple.com) elaborates:
The CD300+ firmware does a much better job of supporting disconnect/ reconnect than did previous Apple CD drives.  The 5.0 CD-ROM driver  supports SCSI Manager 4.3 and will allow disconnects on an CD300+ but not on older drives.
On 4.3 capable machines, I/O to all CD-ROM drives is asynchronous (i.e. the processor gets time back while doing a transfer),  But on a CD300+, the SCSI bus itself is free during this time so that it can be used by other devices...  I don't know of any shipping products that make much use of this but it will eventually help to improve copies from a CD (including digital audio) and other operations which require using both the CD-ROM drive and another SCSI device at the same time.

[AV] Details on expansion
The 660av contains a single multi-purpose slot that can be populated by either a Processor Direct Slot (PDS) card via a plain L-angle adapter, or a DAV + NuBus card via a second more complex adapter containing the MUNI NuBus controller and DAV connector.  The 840av contains 3 NuBus slots and an inline DAV connector on the motherboard, but no PDS for electrical bus loading reasons.
The 660av is only supposed to accommodate a short 7" NuBus card.  However, if the CD-ROM drive bay is empty, you may be able to make room for a full-sized card by moving the hard drive (and mounting bracket as well) over to the middle.  David R. Young (youngd@owl.med.jhu.edu) adds:
Second Wave makes a 4 and an 8 Nubus expansion chassis for the 660AV.  My 4 slot chassis works finewith 2 graphics cards currently installed.  Their phone number is 512-329-9283, and FAX is 512-329-9299.  Remember, you will need the Nubus adapter for the 660AV from Apple.
The PDS of the 660av does support bus arbitration.  However, the unique suite of Application Specific Integrated Circuits (ASIC) found on the 660av prevents the inexpensive Power PC PDS and processor upgrades from working.  For 660av and 840av owners who wish to upgrade to a Power Macintosh, the only solution is the more expensive complete logic board swap.

[Power AV] Details on expansion
You can now purchase the AV Options card separately.  Although only labelled for use with a vanilla 6100, the card can be installed in any other Power Macs after you empty its PDS.  Since the AV card uses the PDS, any 6100/av not only has its only expansion slot occupied, it also winds up with an orphaned DAV connector.
On the 7100/66, synchronization problems exist between the 33MHz system bus and the 10MHz NuBus which results in sluggish transfer rates with high performance cards.  These problems do not exist with the 40MHz system bus of the new 7100/80.
The 8100/80 and its 40MHz system bus is also not affected by NuBus difficulties.  The new 8100/100 (33MHz bus) and the 8100/110 (36MHz bus) both have an updated BART NuBus controller chip that prevents transfer problems.
Apple does not presently offer logic board upgrades to the second generation of Power Macs, this may change as supply ramps up.

Houdini and Houdini II
Officially called the DOS Compatible Card, the original Houdini project pulled its own disappearance act after a limited circulation.  Officially sanctioned only for the 610, this card did not run problem-free when transplanted to other Centris and Quadra systems.  Some reports with a 660av can be found in the Houdini FAQ.
ftp://mirrors.aol.com/pub/info-mac/info/hdwr/houdini-faq-101.hqx

Responding to initial user feedback, Apple has unvealed the Houdini II with a faster 486DX2/66 and SoundBlaster 16-bit sound support, as part of a 6100/66 bundle or retailing separately for $700.  There is no way to gear up Power Macs with both an AV and a Houdini II at the same time, since there is room for only one PDS card.
Reply Corporations (800.801.6898) has licensed the Houdini II technology and plans to market them for 7100/8100 Power Macs and Centris/Quadras with a PDS (this excludes the 840av).  However, they have recently cancelled 660av support due to unspecified reasons.  The lastest product info and news can be found at:
ftp://ftp.csua.berkeley.edu/pub/jwang/misc/houdini-ii.txt

Clock-chipping an AV or Power Mac
Clock-chipping refers to various methods that replace the factory oscillator clock signal (which determines the processor speed) with faster ones that still operate within the system safety and timing margin.  Several models since the IIsi have been thus boosted to between 120% and 140% of the original speed.  The long term consequences of this practice remains to be seen.  Reduced system life span and reliability is likely, mission-critical computers should not undertake this risk.
Warning: although the success rate of these modifications are quoted at well over 90%.  Your mileage may vary, and remember these modifications do void your warranty.  For the electronically adept, Marc Schrier of Output Enablers publishes a how-to on do-it-yourself kits, along with the clock-chipping home page.
ftp://mirrors.aol.com/pub/info-mac/info/hdwr/crystal-speedup-history-23.txt
http://bambam.cchem.berkeley.edu/~schrier/mhz.html

For the electronic neophyte, several companies offer easy to install kits that accelerates most Centris, Quadra, and Power Macs, none requires any soldering.

KS Labs: 660av Booster, 6100/7100 Booster
$99.98 from MacZone (800.248.0800)
6326 E. Livingston Avenue, Suite 131, Reynoldsburg, OH 43068
800.450.0353/order, 614.374.5665/info, 614.373.0353/fax

Newer Technologies: Mac Clip, Power Clip
Allows you to set the CPU speed in fractional MHz increments
$145.98 from MacZone (800.248.0800)

Output Enablers: 660av Rocket ($60), 840av Terburner ($50), PowerClip ($60)
1678 Shattuck Avenue, Suite #247, Berkeley, CA 94709
oe@io.com, http://www.io.com/user/oe/

After acceleration, take care to ensure adequate system cooling.  Do not, for example, run with the case cover open as this completely destroys proper air circulation.  Along the same lines, prevent circulated (heated) air from being drawn back in.  One 660av user placed a foam block between the front intake and the rear exhaust, my own 660av hot-rod is fixed on top of an Apple 16" monitor for the same effect.
If you see evidence of VRAM overheating, where zoom rects start leaving pixel artifacts on the desktop, reduce speed or add extra heatsinks or fan to the VRAM.  Before anyone asks again, my (very stable) 35MHz 660av setup is based on the Output Enabler's 660av-rocket, but with one extra heatsink/fan combo (OE's 040 chiller kit) centered on top of the 8 VRAM chips.

Restart and Interrupt
If your Mac does not sport physical restart and interrupt buttons, the following two keyboard combinations can be used under most circumstances:
Command-Power for interrupt, or programmer's key
Command-Control-Power for restart
Use caution with the restart button or keyboard sequence.  AV and Power Macs will perform a lengthy disk integrity checksum on the next reboot if the machine did not shutdown properly.  This file system check would begin immediately after the happy Mac icon and before the "Welcome to (Power) Macintosh" banner.
During a keyboard soft power restart , a spurious interrupt can be generated if the Power key is held for too long.  This brings up either the mini debugger window with the ">" prompt, or the MacsBug window if you have it installed, type "G" and press Return to resume normal execution.

Soft power on the 660av and 6100
The 660av and 6100 share the same type of case enclosure and power supply as the original Centris 610.  None of these models provide soft power, the ability to power up and power down the computer with the keyboard.  Also, the monitor outlet is not tied to system power, you cannot turn off both the CPU and monitor with the front panel power button.
Soft power and scheduled power can be provided for these models via a product called the PowerKey from Sophisticated Circuits (206.485.7979, 206.485.7172/fax, SophCir@aol.com), for about $70.  Philippe.Astier@scinfo.u-nancy.fr notes that this device only works with 110V systems, and although it can wake up the computer via a phone call, this feature doesn't seem to work with a GeoPort adapter.

SOFTWARE
System software tidbits
The 660av or 840av cannot boot with anything less than System 7.1 and a version of System Enabler 088.  A Power Mac must minimally use System 7.1.2 and the PowerPC Enabler.  System 6 is out of the question, System 7.0 won't cut it either as it does not know how to use System Enablers that contain machine-specific boot info.
Also, both the AV and Power Mac architectures are 32-bit only.  There was once a post in comp.sys.mac.announce that described a 24-bit AV Enabler.  But if you read it carefully, you'll notice it was nothing but a premature April Fool's joke.  (flames to L.H.Wood@lut.ac.uk :-)
Lastly, AV and Power Macs cannot run any version of A/UX.

System software updates
System 7.1 users should install System Update 3.0 for increased stability.  If you decide to upgrade, download the ReadMe and the two 1.44MB installer disk images (the 800K version is for the Mac Plus, SE, and II only) from:
ftp://ftp.info.apple.com/Apple.Support.Area/Apple.Software.Updates/US/Macintosh/System.Software/Other.System.Software/System.Update.3.0.1.4MB.sea.hqx

For Power Mac owners, SU 3.0 installed a faulty PowerPC Enabler 1.0.1 that lost video sync when Video Monitor or FusionRecorder starts up with the monitor set to millions of colors.  PowerPC Enabler 1.0.2 replaced the video digitizer in question and also improved Energy Star compatibility.
ftp://ftp.info.apple.com/Apple.Support.Area/Apple.Software.Updates/US/Macintosh/System.Software/System.Enablers.SW/PowerPC.Enabler.1.0.2.sea.hqx

Besides the features advertised on the System 7.5 box, it has the functionality of SU 3.0 rolled in.  Additional bug fixes and enhancements have been released under System 7.5 Update 1.0, shipping on four high density 1.44MB disk images.
ftp://ftp.info.apple.com/Apple.Support.Area/Apple.Software.Updates/US/Macintosh/System.Software/System.7.5.Update.1.0/

Supplemental System software updates
Version 5.0.x of the Apple CD-ROM setup software added code to handle the AppleCD 300+ and SCSI Manager 4.3, and also includes a sleek new AppleCD Audio Player.  There is a conflict between AAP and the old CD Remote Init, you should trash the extension and CD Remote itself.
ftp://ftp.info.apple.com/Apple.Support.Area/Apple.Software.Updates/US/Macintosh/Display.and.Peripheral.Software/CD-ROM.Setup.5.0.1.img.sea.hqx

Users of QuickTime 2.0 should acquire Apple Multimedia Tuner, which improves performance and reliability during low-memory conditions, even under 7.5.1.
ftp://ftp.info.apple.com/Apple.Support.Area/Apple.Software.Updates/US/Macintosh/System.Software/Other.System.Software/Apple.Multimedia.Tuner.2.0.1.sea.hqx

For the latest Ethernet/TokenRing drivers and general Network Software Installer, NSI 1.5 is available at:
ftp://ftp.info.apple.com/Apple.Support.Area/Apple.Software.Updates/US/Macintosh/Networking.and.Communications/Network.Software.Installer/NSI.ZM-1.5.hqx

PowerTalk 1.1 and QuickDraw GX 1.1.1 were released simultaneously along with System 7.5 Update 1.0, these can be found at:
ftp://ftp.info.apple.com/Apple.Support.Area/Apple.Software.Updates/US/Macintosh/System.Software/PowerTalk/
ftp://ftp.info.apple.com/Apple.Support.Area/Apple.Software.Updates/US/Macintosh/System.Software/QuickDraw_GX/

[AV] ROM patches
Even with System Update 3.0 or System 7.5.1, be sure to install sAVe the Disk 1.4.2 (thanks to Michael Thies) since it does a more thorough job in fixing the 660av/840av ROM bugs.  From the sAVe Read Me:
Several Resource Manager operations flush the whole file to disk each time the length of a resource file is changed.  This significantly degrades performance if many such changes occur in succession, e.g. while linking programs, using ResEdit or running resource compilers.
The disk cache built into the system writes back more data than necessary when flushed.  This does not affect proper operation of the disk cache (nor does it help it :^) but results in superfluous disk activity and thus a slow down of file operations.
Each time a sound channel is allocated (disposed) some information is read from (written to) the file DSP Preferences.  Applications which follow Apple's recommendations create and destroy such a channel for each single sound they produce and thus slow down while they torture your hard disk. This problem becomes most obvious with games
Apple addressed the Resource Manager and disk cache issues with SU 3.0 and improved the cache further with System 7.5.  However, sAVe the Disk completely eliminates the sound channel thrash as well.  It completely replaces any of the following: AV Boost, AV Cache Tuner, AV Resource Manager Tuner, AV Rocket, AV Serial Extension, AV Speedup.
ftp://ftp.csua.berkeley.edu/pub/jwang/misc/save-the-disk-142.hqx

AV Turbo ROM, from Steve Kiene, boosts system performance by copying the ROM to the slightly faster RAM, cutting down access time to the Toolbox.  An obvious drawback is that you lose 2MB of valuable RAM.  Furthermore, AV Turbo ROM cannot coexist with System 7 virtual memory or Connectix's RAM Doubler, and has been known to disable the Finder Restart command.  Also, note the copy ROM to RAM option is stored in the PRAM, you have to turn off Turbo first before you trash the control panel.  Otherwise, the only way to reclaim the 2MB is to zap the PRAM.
ftp://ftp.csua.berkeley.edu/pub/jwang/misc/av-turbo-rom.hqx

Application compatibility
One year after introduction, lingering compatibility problems have all but disappeared.  The following table contains some aged applications and utilities.  The listed version is the earliest version that corrected the problem, though current versions may be several points ahead.
  Adobe Premiere      3.0    Adobe       415.961.4400, 800.447.3577
  Adobe Type Manager  3.6    Adobe Tech  408.986.6505, 800.642.3623
- Disk Doubler Pro    1.1    Symantec    503.465.8440
  DPI-on-the-Fly      2.6    NEC         800.366.0476
  Easy Open           1.0.4  Vendor specific, do not call Apple
  Empower         (1) n/a    Magna       408.282.0900
- FAXstf          (2) 3.01b  STF Tech    800.880.1922, 816.463.7958/fax
  FileGuard           2.8    ASD         909.624.2594
- GlobalFax           2.08b  Global      800.736.4821, 415.390.8334/bbs
  Greg's Buttons  (3) n/a    Greg Landweber (gdl@maths.ox.ac.uk)
- Miracle Piano   (g) 1.4    Soft Tool   800.488.2221
  MultiDisk           1.2.9  Alsoft      713.353.1510, 713.353.9868/fax
  Norton Utilities    2.0.6  Symantec    503.465.8440
  PC Exchange         1.0.5  Apple       800.769.2775, ext 6535
- RAM Doubler     (4) 1.5.1  Connectix   415.571.5100, 800.950.5880
- Ray Dream Designer  3.0.4  Ray Dream   415.960.0767
  Retrospect          2.0b   Dantz       510.253.3000
  SAM                 3.5.9  Symantec    503.465.8420
- SoundEdit Pro       1.0.5  Macromedia  415.252.2000, 800.945.4061
  Stacker         (5) n/a    Stac        619.431.6712
- Suitcase II         2.14p1 Symantec    503.465.8440
  Swivel 3D           2.0.4  Macromedia  415.252.2000, 800.945.4061

(1) incompatible with HD SC Setup, works with 3rd-party drivers.
(2) must request new modem drivers in addition to updater.
(3) "Colored Buttons" are not recognized by PlainTalk Speech Recognition.
(4) all versions conflict with AV DSP Power and AV Turbo ROM; 1.5.0 and prior also conflicts with the SCSI Manager 4.3 extension from System 7.5.
(5) update driver with HD SC 7.2.2 or later, "disconnect" Stacker first.
(g) incompatible with GeoPort, patch with ASFU Fixer.
ftp://ftp.csua.berkeley.edu/pub/jwang/geoport/asfu-fixer-101.hqx
ftp://mirrors.aol.com/pub/info-mac/cmp/disk-doubler-pro-11-updt.hqx
ftp://mirrors.aol.com/pub/info-mac/app/fax-stf-30-to-301b-updt.hqx
ftp://pmail.globalvillag.com/pub/software/TelePort_Serial.sea.hqx
ftp://mirrors.aol.com/pub/info-mac/cfg/ram-doubler-151-updt.hqx
ftp://mirrors.aol.com/pub/info-mac/grf/util/ray-dream-designer-30x-to-304-updt.hqx
ftp://mirrors.aol.com/pub/info-mac/snd/util/soundedit-pro-105-updt.hqx
ftp://mirrors.aol.com/pub/info-mac/gui/suitcase-214p1-updt.hqx

Game compatibility
Some games dropped dead because of the strict 32-bit architecture of an AV or Power Mac, while a greater number of them simply became mute.  The latter usually happens when programmers write directly to an Apple Sound Chip (ASC) that's no longer used.  Again, this situation no longer affects current releases, but as they say, the classics never die.
To check if a specific game is known to be incompatible or problematic, inspect the list maintained by Brian S. Lev (lev@nssdca.gsfc.nasa.gov):
ftp://ftp.csua.berkeley.edu/pub/jwang/broken-games.txt

[AV] Software that employs the DSP
The AT&T DSP3210 is a specialized floating point processor that excels at, well, signal processing.  While its 20-odd MFLOPS (millions of floating point instructions per second) is not useful for general purpose computing, the DSP is extremely adept at real-time processing and used commonly for the following routines:
Apple Phone
GeoPort and Express Modem emulation
PlainTalk Speech Recognition (SR), but not Text-to-Speech (TTS)
System sound effects and sound rate conversions
There are a handful of third-party DSP-savvy programs.  Note the AV DSP Power plug-in for PhotoShop is not entirely stable and bug-free, it conflicts with all versions of RAM Doubler and has at least one memory leak.  Adobe no longer recommends using this accelerator, and Spectral Innovations does not seem interested in fixing it up either.
- ARTAbrot            1.2.1  George Warner (warnergt@aloft.att.com)
- AV DSP Power        2.5    Spectral I. 408.955.0366
  Deck II             2.1    OSC         415.252.0460
  DigiTrax            1.0    Alaska      800.500.3320
  Painter X2          2.0    Fractal     408.688.8800, 800.647.7443
  VideoFusion         1.5    VideoFusion 419.891.1090
- VUMeters            1.0    Malcolm Slaney (malcolm@apple.com)

ftp://ftp.csua.berkeley.edu/pub/jwang/develop/artabrot-121.hqx
ftp://mirrors.aol.com/pub/info-mac/grf/util/photoshop-av-dsp-filters.hqx
ftp://ftp.csua.berkeley.edu/pub/jwang/develop/vumeters-10.hqx

[AV] Developing software for the DSP
Apple licensed the official DSP3210 develop kit to the DSP specialists at Spectral Innovations (408-955-0366) for distribution.  The original kit price of $1000 has been reduced to $400, also reduced was the amount of technical support.
The official kit did not sell well, at either price.  Work has been underway by several enthusiasts to produce a freeware DSP3210 assembler.  Version 0.13 is the latest offering before the principal architect, Paul Lalonde, was hired for a new full time job (lalonde@infinity.metrowerks.ca).  The early results are promising, some assembled binaries even match byte-for-byte with ones from the official kit.
Paul's advice for potential DSP developers include:
You will also need the following two documents:
1. The AT&T "DSP3210 information manual" which describes the DSP's instruction set.  You can get it for free from AT&T by phoning them at 1-800-372-2447.
2. The "Centris 660AV & Quadra 840AV" developer note, which describes the DSP operating system (aka ARTA).  It's on the more recent Bookmark CDs.
If you are interested in filling the DSP black hole left behind after the push for native Power PC code, whether you are a veteran of the digital signal processing paradigm or a beginner willing to get your feet wet, check out the DSP dedicated development directory at the AV pit stop.  Technical documentation and other developer resources are also available at:
ftp://ftp.csua.berkeley.edu/pub/jwang/develop/
ftp://ftp.csua.berkeley.edu/pub/jwang/av-pmac-audio.rtf
ftp://ftp.cs.jhu.edu/pub/dsp/
ftp://ftp.info.apple.com/Apple.Support.Area/Developer_Services/Technical_Documentation/

SCSI Manager 4.3 introduction
Built-in to AV and Power Macs, and provided by System 7.5 for most other 040 CPU's (030 and older models lack the necessary 53C94/53C96 SCSI controller), SCSI Manager 4.3 is designed to break through previous I/O bottlenecks.  The major additions include SCSI disconnect/reconnect, fully asynchronous operations, SCSI DMA, and better SCSI-2 and multiple SCSI buses support (through add-on cards).
While the raw byte transfer rate is not boosted due to hardware limits, system level and real-world performance can be greatly increased by returning control back to the user immediately after SCSI I/O requests are issued, rather than when they complete.  With disconnect/reconnect, multiple requests can execute in parallel on multiple targets, perfect for disk arrays.  With the DMA capability found on AV's and Power Macs, the CPU is relieved of even more baby-sitting duties.
To take advantage of what SCSI Manager 4.3 provides, you must update the existing driver and client application.  You can still use non-4.3-savvy drivers without fear of data loss, albeit under a compatible mode that's much slower, not to mention the same performance bottlenecks as before.  TidBITS issue 251 has much more detailed discussion of SCSI Manager 4.3 and its impact.
ftp.tidbits.com/pub/tidbits/issues/1994/TidBITS#251_07-Nov-94.etx

SCSI Manager 4.3 versions
There are at least 5 versions of note, in revision order:  the buggy developer pre-release SCSI Manager 4.3f1, one burned in the AV ROM, one in the Power Mac ROM, the standalone SCSI Manager 4.3 extension that comes with System 7.5, and finally version 4.3.1 from System 7.5 Update 1.0.
If you have System 7.1, you should stick with the ROM.  Running either standalone  extension without 7.5 is not recommended, since the System suitcase itself has tweaks to match those in the new extensions.  If you have a Power Mac, you should also stick with the ROM.  The 4.3.1 extension only provides bug fixes to the AV and PowerPC card upgraded Centris and Quadras.  The only folks that need SCSI Manager 4.3.1 are 660av and 840av owners running System 7.5.1.
RAM Doubler needs to be updated to version 1.5.1 before it can co-exist peacefully with the standalone extensions.
ftp://mirrors.aol.com/pub/info-mac/cfg/ram-doubler-151-updt.hqx

SCSI Manager 4.3 savvy drivers
On AV and Power Macs, both the built-in internal hard drive and CD drive should already be SCSI Manager 4.3 ready.  Apple HD SC Setup has supported SCSI Manager 4.3 ever since version 7.2, and CD-ROM Setup since 5.0. 
To check if your driver is 4.3 savvy, open the Apple HD SC Setup program, and navigate to the partition entry screen (hit the "Partition" and "Details" button in succession).  If the Apple_Driver entry lists a partition type of Apple_Driver43, you are all set.  If not, it is highly recommended that you update the driver.  HD SC Setup can do this for factory formatted hard drives from Apple, and a limited number of others with the following patch:
ftp://mirrors.aol.com/pub/info-mac/disk/apple-hd-sc-setup-731-patch.hqx
ftp://mirrors.aol.com/pub/info-mac/disk/apple-hd-sc-setup-732-patch.hqx

The following commercial formatter and utility packages are also 4.3 savvy:
  Anubis              2.5    CharisMac   916.885.4420, 800.487.4420
  APS Power Tools     3.0    APS Tech    800.443.4199
  CD-ROM Toolkit      1.5.1  FWB         415.474.8055
  Drive7              3.0    Casa Blanca 415.461.2249
  Hard Disk Toolkit   1.6    FWB         415.474.8055
  Micronet Utilities  6.0.0  Micronet    714.453.6000, 714.453.6063/BBS
  Retrospect          2.1    Dantz       510.253.3000, 800.225.4880
  SCSI Director Pro   3.0.7  Transoft    805.565.5200, 800.949.6463
  SilverLining        5.6    La Cie      503.520.9000

VIDEO INPUT & OUTPUT
Graphics and Video independence
An important concept inherent in the AV frame buffer technology is the independence between standard Macintosh graphics (windows and desktop) and live video input (from either input jacks).
The frame buffer consists of two banks (video and graphics) that equally split the available video memory (1MB or 2MB).  Both halves are usually combined to provide the highest possible color depth for graphics alone.  When actively displaying video-in, the graphics memory usage must be reduced to fit within its own bank or the video window will be blank with an appropriate error message.
To reduce the graphics memory usage, lower the number of colors in the Monitors control panel, or via shortcuts like AppleScript, DepthCharge, or heaven-forbid, Speech Recognition.  Keep in mind that any color depth change only affects desktop graphics, live video will always plays through at 16-bit (thousands of) color or 8-bit (256) grayscale.
ftp://mirrors.aol.com/pub/info-mac/cfg/depth-charge-17.hqx

Graphics: monitors and resolutions supported
The built-in monitor ports of previous Quadra and Centris models provided synchronization signals on the green output pin.  This sync-on-green has been removed from all models since then.  While this presents no problems for Apple monitors that rely on sync signals on separate pins, various third-party monitors expect or demand sync-on-green, contact the manufacturer for a possible replacement cable or adapter.
The following display table is almost verbatim from the 660av and 840av overview from Noah Price (noah@apple.com), it fully applies to the 2MB VRAM Power AV card (but not the Power Mac built-in DRAM video nor the HPV PDS card video).  The color depth ranges are indicated with bits-per-pixel (bpp) definitions, which include:
1 bpp - Black & White
2 bpp - 4 colors or grays
4 bpp - 16 colors or grays
8 bpp - 256 colors or grays
16 bpp - Thousands of colors (5 bits each R, G, and B; 1 bit alpha channel)
32 bpp - Millions of colors (8 bits each R, G, and B; 8 bits alpha channel)
Entries with an asterisk (*) are the default resolution for a particular display, reduce the resolution to gain more available colors.  On multi-sync monitors, different resolutions occupy the same screen area.  On mono-sync monitors, the pixel size is constant and the image area is not.  Hashed entries (#) indicate when video-in is available at the highest graphics bit depth.

                                  1 MByte VRAM - bpp  2 MByte VRAM - bpp
                                  ==================  ==================
Display               Resolution  Graphics  Video-in  Graphics  Video-in
------------------------------------------------------------------------

12" RGB                512x384*     1-32      8-16      1-32      8-16
                       560x384      1-32      8-16      1-32      8-16

13" or 14" RGB         512x384      1-32      8-16      1-32      8-16
& 12" Monochrome       640x400      1-32      8-16      1-32      8-16
                       640x480*     1-16      8-16      1-32      8-16

15" Portrait           512x384      1-8#      8-16      1-8#      8-16
Full-Page Monochrome   640x480      1-8#      8-16      1-8#      8-16
                       640x870*     1-8       8-16      1-8#      8-16
 
15" Portrait RGB       640x870*     1-8       8-16      1-16      8-16
 
16" RGB                512x384      1-32      8-16      1-32      8-16
                       640x480      1-16      8-16      1-32      8-16
                       768x576      1-16      8-16      1-32      8-16
                       832x624*     1-16      8-16      1-32      8-16
 
19" RGB               1024x768*     1-8       8         1-16      8
 
21" Two-Page           512x384      1-8#      8         1-8#      8
Monochrome             640x480      1-8#      8         1-8#      8
                       768x576      1-4#      8         1-4#      8
                      1152x870*     1-8       8         1-8#      8
 
21" Two Page RGB       512x384      1-16      8         1-16      8
                       640x480      1-16      8         1-16      8
                       768x576      1-4#      8         1-4#      8
                      1152x870*     1-8       8         1-16      8
 
VGA/SVGA Displays      640x480*     1-16      8-16      1-32      8-16
                56Hz   800x600      1-16      8-16      1-32      8-16
                72Hz   800x600      1-16      8-16      1-32      8-16
                60Hz  1024x768      1-8       8         1-16      8
                70Hz  1024x768      1-8       8         1-16      8
 
VIDEO-OUT, NTSC convolved (flicker-free mode)
 Underscan (Safetitle) 512x384      1-8       NA        1-8       NA
 Overscan  (Fullframe) 640x480*     1-8       NA        1-8       NA
 
VIDEO-OUT, NTSC non-convolved
 Underscan (Safetitle) 512x384      1-32      8-16      1-32      8-16
 Overscan  (Fullframe) 640x480*     1-16      8-16      1-32      8-16
 
VIDEO-OUT, PAL convolved (flicker-free mode)
 Underscan (Safetitle) 640x480      1-8       NA        1-8       NA
 Overscan  (Fullframe) 768x576*     1-8       NA        1-8       NA
 
VIDEO-OUT, PAL non-convolved
 Underscan (Safetitle) 640x480      1-16      8-16      1-32      8-16
 Overscan  (Fullframe) 768x576*     1-16      8-16      1-32      8-16

Graphics: maximum color depth
With a 1MB frame buffer and video-in disabled, the Millions of colors mode simply is not possible on monitor resolutions greater than 640 by 400.  Use the Options dialog box in the Monitors control panel to reduce the display resolution and video memory usage.  Depending on the monitor, choose either the 640x400 or 512x384 setting and 32-bit color will be enabled when the new resolution takes effect.
Similarly, with 2MB of video memory, 32-bit color is only possible at or below the standard 16" resolution of 832x624.  With video-in active, kiss Millions of colors good-bye, unless you are using a resolution not greater than 640x400.

Graphics: switching resolutions on-the-fly
For Apple monitors, the Apple Display Enabler can take advantage of the capabilities of built-in video to switch resolutions on-the-fly (with the Rearrange On Close option selected).  With the Display Enabler and an Apple Multiple Scan monitor, the screen will resize to fit to the new resolution dynamically.  For older mono-sync monitors, the display area is altered along with a change in the width of the surrounding black border.  Without the aid of such switching software, a reboot is necessary before resolution changes take effect.  System 7.5 has the Display Enabler built-in, 7.1 users can find the software at:
ftp://ftp.info.apple.com/Apple.Support.Area/Apple.Software.Updates/US/Macintosh/Display.and.Peripheral.Software/Display.Software.1.2.sea.hqx

The Display Enabler software is also included if you buy one of the new Apple Multiple Scan monitors.  However, the 660av and 840av ROM do not recognize the new sense codes on these monitors.  The AV will treat the 17" and 20" monitors as a television and boot in 640x480 mode as a precaution.  When the Display Enabler finally loads sometime later, the monitor will re-sync to the correct display size.  This problem lies with the ROM, and a software solution is unlikely.
This sense code problem does not occur with third-party multi-sync monitors, which usually include their own DPI-on-the-fly software or resolution adapter.  VGA multi-resolution adapters should have pins 7 and 10 shorted, offering display sizes of 640x480, 800x600, and 1024x768.

Video-in: performance, quality, and limits
Video-in on all AV models is handled by a CPU-independent Philips chipset similar to that found on the VideoSpigot.  Several other pieces of specialized hardware add to deliver arbitrary size video (up to 640 by 480 NTSC, or 768 by 576 PAL) at full motion (30 fps NTSC, 25 fps PAL).  The video controller and scaler chips require no CPU intervention once the settings are agreed upon, video continues to blast through even in the event of a system crash.
On 16" or smaller monitors, live video-in is shown in either 16-bit color or 8-bit grayscale, independent of the desktop graphics color depth.  On 19" or larger monitors which have higher refresh rates, video-in is limited to 8-bit grayscale only, irrespective of the VRAM size.
Even with the proper signal (NTSC/PAL/SECAM) and filter (TV/Laser/VCR) settings, you may still find the default 16-bit color video quality inadequate for scientific and image analysis purposes.  The analog to digital converters (ADC) are only 8-bit wide.  S-Video handles luminance and chrominance data separately with dual ADC's, but still only at 8-bits each.  The AV hardware then convert the digitized wave forms to 16-bit YUV or 24-bit RGB (when you video capture using the Component Video - YUV codec).  Therefore, you will never get a true 24-bit color image from the digitizer.

Video-in: built-in video vs. video cards
To access the video digitizer, you must be using the 660av/840av built-in monitor port, or the AV card monitor port on a Power AV.  If you have a monitor being driven by a third-party video-card and don't want to invest on another just for live video display and capture, install an orphaned monitor plug to trick the computer.   However, since video data must make another bus hop from the "virtual monitor" to the actual display, this trick will result in less than optimal quality and results.
On virtual monitors, Simon Chapman (simon@slicker.demon.co.uk) adds:
Certainly the cursor can slide out of site if you're not careful--and it can be fun (NOT) trying to get it back. The way to minimise this is to drag the icon of the virtual monitor inside the Monitors CDEV so that it adjoins the actual monitor at one corner only instead of a flush join at the side. It will still be possible to 'lose' the cursor--but at least you know which direction to reel it back in from!  Also a corner join means that windows can't slide off the real monitor.

[AV] Video-in: 1MB frame buffers and more limits
If you have a 660av or 840av equipped with only 1MB of video memory, you might have noticed the line-doubling phenomenon when displaying video at full screen.  The effect is easy to spot up close, every other horizontal scan line is duplicated since there isn't enough memory for all 640 x 480 video pixels at 16 bits-per-pixel (bpp) color.
If you own a 840av, adding another 1MB of VRAM (4x256K SIMMs) is the best way to eliminate line-doubling.  For the budget conscious, one can lower the video memory requirement just by resizing the video window to 496 by 372 or lower, aspect ratio may vary.  FusionRecorder can even crop the capture region, handy for digitizing letterboxed movies.  Moving video windows partially off screen will also do the trick.  However, video capture using this second option is not desirable since the region off screen comes out as garbage.
Another solution exists if you don't mind dealing with grayscale video.  With AV Digitizer Options installed, you can voluntarily downgrade the video color space to 8-bit gray instead of 16-bit color.  This reduces the video memory usage in half and result in a full 640 by 480 video image that fits inside the 0.5MB video bank.  With this extension, you also get control of inverse gamma correction and 8-step video/graphics transparency.
ftp://ftp.csua.berkeley.edu/pub/jwang/video/av-digitizer-options.hqx

Video-in: Video Monitor replacements
Video Monitor is the only program able to convert 16-bit YUV images to 24-bit RGB during a freezed frame capture.  With full screen video-in, however, such a capture requires a memory allocation of 6MB.  For the very highest capture quality, be sure to turn off compression in the Preferences menu item.
Video Monitor's future as a television watcher is not as bright.  With QuickTime 2.0, live playthrough becomes choppy or frozen when other windows clip the monitor window.  I recommend Apple Video Player as a possible replacement, with unique interface features such as mode-less volume/brightness/sharpness/tint controls.
ftp://ftp.info.apple.com/Apple.Support.Area/Apple.Software.Updates/US/Macintosh/System.Software/Other.System.Software/Video.SW.Installer.1.0.4.sea.hqx

Suppose you find the controls bar on the right side of the video window a waste of screen real estate, just use ResEdit to open the 'Conf' 1000 resource and change the "Controls Width" value from 60 to 0.
One disadvantage of AVP is the loss of AV Digitizer Options access and the ability to voluntarily drop down to gray scale video.  If this is important for line-doubling reasons, there are also a plethora of virtual Video Monitor clones:
ftp://ftp.csua.berkeley.edu/pub/jwang/video/video-monitor-pro.hqx
ftp://ftp.csua.berkeley.edu/pub/jwang/photo-capture-11.hqx
ftp://mirrors.aol.com/pub/info-mac/grf/util/desktop-tv-150.hqx
ftp://mirrors.aol.com/pub/info-mac/grf/util/tv-monitor-101.hqx

Video-in: television tuner
The composite and the S-video input ports are designed for flexibility with sources such as a VCR, Laser Disc player, or camcorder.  Straight television signals must demodulate through an external tuner or VCR before they are ready for the AV.  Although internal tuner cards are available for the Macintosh TV and the 63x TV/Video system, they are not compatible with any of the true AV's.
Philippe.Astier@scinfo.u-nancy.fr managed to discover an internal tuner for the European market:
The card is called D2 TV Tuner card. It is a PAL/SECAM tuner  that fits in a NuBus Slot, in the video-in and audio-in ports. It also features an infrared remote control and keyboard control, for both the tuner and CD-ROM drisc drive. They sell it all over Europe, for about 1200 FF (~US$200).

Video-in: video conference
One popular AV compatible video conference program for TCP-based Macintosh computers is CU-SeeMe.  Please refer to the CU-SeeMe FAQ and information sites below, references thanks to Don White (white_d@hccs.cc.tx.us):
ftp://gated.cornell.edu/pub/video/
http://pogo.wright.edu/cuseeme/cuseeme.html
http://www.ludvigsen.dhhalden.no/webdoc/video.html

Video-out: starting it up
Before attempting to display the Macintosh desktop on a video projector, VCR, or television, attach the device to either the composite or S-Video output jack.  At this point, open the Monitor control panel and go to the Options dialog box.  Choose Display Video on Television and acknowledge the subsequent warning.  If the selection happens to be disabled, first switch to a television comparable resolution (512x384 or 640x480 NTSC, 640x480 or 768x576 PAL) and then try the above.
Video-out and the RGB monitor port cannot be active simultaneously.  The RGB monitor will turn blank after you dismiss the final warning, and if all goes well, you will see the desktop on the video-out device.  If something went wrong and you lost the picture, hit Command-S and to save any work in progress and then hit the Power key.  This will bring up the shutdown confirmation dialog box, though you can't see it, press Return for the go-ahead and wait for disk activity to cease before restarting.  The AV will by default boot on the RGB monitor if it's still attached.
The manual also describes two additional methods to startup video-out, including checking the Upon Restart Display Video on Television option and rebooting, or holding down Command-Option-T-V (only for NTSC) during restart and letting go when video appears on the desired device.  These two methods require that the RGB monitor be disconnected from the computer, cumbersome as it may be.
If you have just upgraded to System 7.5 and find your AV incapable of starting video-out (the choices are grayed out in the Monitors control panel), you need to put the Quadra AV Monitors Extension back in the starting lineup.  This poorly named extension have been (many times) mistaken as something only needed for the AV Monitor.

Video-out: flicker reduction
If Use flicker-free format is turned off in the Monitors control panel, you will immediately notice the video-out flicker effect.  Due to their outdated interlaced display technology, television sets will have the most problems with single pixel wide horizontal lines placed one pixel apart, i.e. window title bars.
The flicker reduction option, also known as Apple convolution, time averages the pixel values over multiple cycles for a perfectly stable image, but with a trade off in picture sharpness and small text readability.  This option is not available when video-in is active, or if graphics is at higher than 8-bit color.  Your presentation strategy with any video-out mode should include using thicker lines, larger or boldfaced fonts, widely spaced objects, etc.

Video-out: overscan versus underscan
When using video-out, take note of the difference between overscan mode (full-frame, NTSC 640x480) and underscan mode (safe-title, NTSC 512x384).  With overscan, regions of the screen, including the menu bar, will be cropped and off-screen on ordinary television sets.  On the other hand, full screen visibility is guaranteed with underscan, except this means using the lowest possible resolution.
If you cannot afford to sacrifice any screen real estate for a particular presentation, use the overscan mode, but you must adjust the layout to fit the particular TV or projector you intend to use.
Lastly, with the Display Enabler installed, turning on flicker reduction complicates switching between the overscan and underscan modes.  You will notice no change if you just select a resolution of the opposing mode.  The workaround is tedious but simple: first disable flicker reduction and close the Options dialog box; now enter it again and choose between the non-convolved settings.

Video-out: video mirroring
Video mirroring PowerBook style, or displaying the exact same image on both the RGB monitor and a television or projector via video-out, cannot be done on any AV or Power AV out of the box, since both a RGB and a NTSC or PAL formatted signal is demanded from the same video memory and circuitry.  If such a setup is absolutely required, you need to acquire a special split cable to drive a VGA-compatible monitor and feed a separate external encoder box.

Video-in, Video-out: subtitling potential
The on-board video-in does not support genlock, but without the aid of a hardware genlock board, users have experimented with masking graphics and text over video-in, the result of which may be piped through to video-out and displayed on a television or recorded on a VCR.  In other words, using both video-in and video-out simultaneously.
When trying this out yourself, just remember to disable the default Use flicker-free format option, or else face the familar disabled digitzer error dialog.  This is a "normal" side-effect brought about by the extra timing requirements of frame buffer convolution.  Noah Price (noah@apple.com) explains:
In addition to the technical difficulties, you really don't want convolution on a video-input playthrough window.  Ideally we could convolve just the graphics portion, leaving the playthrough window unconvolved, but that would be even more difficult.
To take advantage of color masking, you are also limited to palette mode graphics, or 256 colors or less.  One single color of the graphics palette is always masked out when mixed with video.  Place the Monitors control panel spectrum bar over Video Monitor to identify the particular color.  Items superimposed over a background of the mask color will appear to float if the graphics is placed over the video window.
MovieTrilogy, from Paul C. H. Ho (paulcho@io.org), promises to simplify this process greatly.  Consisting of separate but cooperative programs, this shareware suite allows users to set the mask color, script text and graphics, and coordinate the overlay sequence.
ftp://mirrors.aol.com/pub/info-mac/grf/util/desktop-movie-150.hqx
ftp://mirrors.aol.com/pub/info-mac/grf/util/desktop-text-150.hqx
ftp://mirrors.aol.com/pub/info-mac/grf/util/desktop-tv-150.hqx

Video capture: stock performance
Without dedicated compression hardware, stock AV's lack the horsepower to digitize full-motion video at full-screen, or 30 frames per second (fps) at 640 by 480.  To squeeze out the best results, observe the following cost-effective tips:
1)	Optimize your hard drive for a large contiguous block of free space.  Fragmentation can cause dropped frames when recording first to disk.
2)	Load as few extensions as possible, QuickTime and sAVe the Disk are suffice.  You can certainly do without Apple CD-ROM, Foreign File Access, Express Modem/Fax, etc.  Along the same lines, disable File Sharing and turn off all network connections.
3)	Run only the Finder and the video capture program, which should be allocated all but 1 or 2MB of your free RAM (for QuickTime scratch).  The Disk Cache should be no more than 128K, Virtual Memory off.
4)	Save the frames uncompressed (check Post Compress or choose None as the compressor under Video Settings).  Save to RAM if the recording is relatively short.  When dealing with extended footage, consider either saving to disk (if RAM is limited) or compression-on-the-fly (if disk is limited), or both.
	Video is a speedy compressor/decompressor (codec) fit for on-the-fly cases.  Cinepak packs better and playback is superb, but compression is slow as molasses (taking about one minute per one second of footage), it is only suited for post-production final output.  Information on some other codecs can be found on pages 9-10 of the FusionRecorder Read Me, initially in your Apple Extras folder.
5)	Also within the Compression pop-up, set Frames per second to "Best" which saves as many frames as the digitizer and drive would allow.  Change this rate only if the system can keep up and you are trying to conserve space, specifying an artificially high rate will result in useless and wasteful duplicate frames.
The average capture figures below should give folks an idea of what to expect.  These numbers are non-authoritative, as they come from separate sources and methods, use them for reference only.  Many factors out of the user's control can affect the final outcome, even the image content (i.e. a pitch black screen will compress much faster and smaller than a typical MTV video). 

                        Save    (*)Average Capture Frame Rate (fps)
Frame Size   Compressor  To     (1)660AV   32MHz   35MHz   840AV(2)
-------------------------------------------------------------------
640 x 480       Video   disk         1       1       1       1
(Full)          Video   memory       1       1       1       1
                None    disk         1       2       2       2
                None    memory       4       4       5       1

320 x 240       Video   disk         3       3       4       3
(Half)          Video   memory       3       3       4       3
                None    disk         7       8       8       9
                None    memory      20      25      26      27

240 x 180       Video   disk         4       5       6       5
                Video   memory       5       6       6       6
                None    disk        11      13      15      16
                None    memory      26      29      30      29

160 x 120       Video   disk        10      12      13      13
(Quarter)       Video   memory      10      12      13      14
                None    disk        26      27      28      22
                None    memory      30      30      30      30

(*)	These results determined with QuickTime 1.6.1, version 2.0 is available offering up to 25% better capture and even better playback performance.  Also, if anyone with a Power AV has done similar capture benchmarks, I would appreciate any numbers you can contribute.
(1)	660av 16/230/CD at stock and two "clock-chipped" speeds, FusionRecorder (12MB RAM partition) used for capture, Adobe Premiere 3.0 (Movie Analysis tool) used for analysis.
(2)	840av 16/230/CD at stock speed (40MHz), Premiere 3.0 used for capture and analysis.  Many thanks to michael_whitney@qm.claris.com.

Video capture: professional performance
The necessary data rate for full-screen NTSC video (640 by 480 pixels at 30 frames per second) is 18.43 MB per second.  Full-screen PAL video (768 by 576 pixels at 25 frames per second) bumps the requirement to 22.12 MB/s, either of which is far higher than the 5MB/s limit of the built-in SCSI bus.
For professional quality results, add items such as extra RAM, disk arrays and controller cards, or high capacity hard drives such as the Micropolis AV series, which turns off thermal recaliberations during disk activity and guarantees a minimum sustained transfer rate.
Unless you have the non-expandable 6100av, you may also consider DAV-based compression cards that boast 640 by 480, 30 fps capture and playback.  The EyeQ/AV is one such card using Indeo technology, retailing for $1895.  Contact New Video Corp, 310.449.7000, 310.449.0132/fax.  SuperMac/Radius (800.334.3005) is the only other DAV player with SpigotPower AV, at a street price of $800.
The SPAV accelerates capture and playback via hardware assisted JPEG and interlaced  JPEG codecs.  Note that interlaced JPEG is required if you capture above 240 scan lines or over 30 frames per second.  Interlaced JPEG will not look good on standard non-interlaced computer monitors, as it is intended for interlaced NTSC output (i.e. full screen, 60 fields per second video) .  If you want to work with interlaced video, this card is great.  If not, you can probably push 320x240x30 fps on a clock chipped AV (given enough RAM).
At least, that was the impression from Glen Speckert (GCSpeckert@TASC.com), several other rants and reviews on the SPAV can be found at:
ftp://ftp.csua.berkeley.edu/pub/jwang/video/spigot-power-av.txt

Video capture: quality is job #1
Here are some miscellaneous AV discussions culled from the Apple Computer Tech Info Library at gopher://info.hed.apple.com.
Black band appearing at the bottom of my images
The black band is most likely  the blanking part of the video frame.  The AV digitizer expects a certain number of lines and we've have seen this occur on other video digitizers. The signal contains the blanking information and is normally outside the display area of the typical television monitors.
Due to the vast amount of history with the NTSC standard, there is some "freedom" about exactly how blanking works. If the number of image lines the AV digitizer is expecting is more than what the source supplies, there will be visible blanking info at the bottom of the image (or at times, on one of the edges).
When capturing still frames it is relatively easy to fix these captured images using an application like Photoshop or Painter. Simply use their tools to crop out the unwanted area. While not  an ideal solution, it is only one available to eliminate this part of the display. Some video capture applications provide a crop rectangle so that cropping can be specified prior to the capture.
Extremely bright S-Video images
Based on what the AV expects in a video signal, it is possible to over saturate the bright areas of an image. Over saturation is easier to introduce with S-video because you have a stronger signal available.  Choosing the VCR option (instead of the TV/video disc option) in the video input control panel provides the best setting in such situations. The best way to control the brightness is during the shooting of the video. Keeping the contrast ratio as low as possible will provide the best results.
Randall Voth (hvoth@cln.etc.bc.ca) has his own tip for an over-saturated cable signal.  Simply insert two common 75-to-300 ohm converters back to back for attenuation (cable -> 75/300ohm -> 300/75ohm -> VCR -> AV).
Capture at field versus frame resolution
There are two issues to consider in the area of video resolution versus computer pixels. First, the output of the analog video device does not always map directly to the pixel count of the digital device.
Second, concerns the number of pixels that are captured by the AV system. Based on VRAM of 1MB, a true 640x480 image can not be captured.  A 640x480 image can be created, but it will use line-doubling from single field to produce the full screen image. To get a full 640x480 image using both fields 2MB of VRAM is required. The 1MB limits the dual field/undoubled line image to 496x372 pixels.
Some additional thoughts to consider on single field versus single frame, which uses both fields: If the capture image is 240 or less lines vertical 1 field is dropped to scale the image. Two examples:
First case, 1MB VRAM - if the capture image is greater than 240 lines vertical or is equal to/less than 372 lines vertical, then both fields are used. A scalar chip is used to scale the information from the two fields.
Second case, 2MB VRAM - if the capture image is greater than 240 lines vertical, up to 480 lines vertical, both fields are used. Again a scalar chip is used to scale both fields to the selected image size.

AUDIO INPUT & OUTPUT
Audio-in, Audio-out: hardware specifications
From the Developer Notes, identical for both the AV and Power Macs:
Audio In: 8 kilo-ohm impedance, 2 V rms maximum, 22.5 dB gain available.
Audio Line Out: 37 ohm impedance, 0.9 V rms maximum, attenuated –22.5 dB (crosstalk degrades from –80 dB to –32 dB when the audio output is connected to 32 ohm headphones).
Sound I/O bandwidth is 20 Hz to 20 kHz, plus or minus 2 dB.  Total harmonic distortion and noise is less than 0.05% over the bandwidth with a 1 V rms sine wave input. The input signal-to-noise ratio (SNR) is 82 dB and the output SNR is 85 dB, with no audible discrete tones.
Ben Denckla (bdenckla@fas.harvard.edu) has written an excellent field guide for audiofiles interested in the capabilities of AV digital audio.
ftp://ftp.csua.berkeley.edu/pub/jwang/av-pmac-audio.rtf

Audio-in: line level and the PlainTalk microphone
The AV are the first Macs to handle line-level audio input directly, a trend for all new models out of Cupertino.  This translates to less hassle with external audio sources and greater dynamic range, but does present a problem for weakly-powered microphone inputs.
The original Apple omni-directional disc mic is no longer usable.  The PlainTalk microphone (part number M9060Z/A, about US$25), with a built-in preamplifier for line-level output, is required by any AV, Power Mac, LC475, or Quadra 605, etc.  Note the 0.75" long PlainTalk microphone plug, which uses an unique all-in-one design to channel +5Vdc power (tip), mono sound (ring), and ground (sleeve).
Do not worry about standard 0.5" stereo mini-plugs.  If the signal is line-level (some externally or battery powered mics, for example), the standard plug will work.  In rare cases, you may need to shave a bit off the plastic ring on the sound-in port for optimal fit.  With external line-level audio sources, you will likely require a dual RCA phono plug to stereo mini-plug adapter.  Purchase a Radio Shack Y-adapter or equivalent.  However, do not use the original Apple Y-adapter designed for LC's and PowerBooks, which attenuates the signal back down to mic-level.
Written by Malcolm Slaney (malcolm@apple.com), the utility VUMeters is extremely useful when testing audio input and output, its Read Me states:
This application measures the sound level at the input and output of the DSP sections of the Macintosh AV computers.  Use it to verify that you have sound connected to the sound input of the Macintosh AV computers.
ftp://ftp.csua.berkeley.edu/pub/jwang/develop/vumeters-10.hqx

Audio-in: multiple input sources and playthrough
CD-equipped AV's and Power Macs consider the internal CD a separate input source apart from the microphone or external audio port.  The Sound In pop-up panel of the Sound control panel is supposed to manage between the multiple sources.  For example, to hear an audio CD, you should first select the internal CD as source and check playthrough.  If you are greeted by a "The sound input device options cannot be accessed at this time" error message, turn off programs that lock the sound setting, including the Express Modem and Video Monitor, and try again.
However, sound settings do not "stick" between restarts on Power Macs without System Update 3.0.  Even then, programs that keep private sound settings, Video Monitor for one, tend to mangle the settings after they finish.  To juggle between the input options efficiently and effortlessly, check out my freeware application CD Playthrough, which also handles the sound output rate.
ftp://ftp.csua.berkeley.edu/pub/jwang/audio/cd-playthrough-16.hqx

Audio-out: sound out rate frequencies
An AV can output sound at 22.050, 24.000, 44.100 (CD standard), and 48.000 (DAT) kHz, while a Power Mac can output at 22.050 and 44.100 kHz.  Rate conversions to the higher frequencies are handled by the Real Time Manager, which in turn send the task to the DSP or the Power PC processor.  When playing an audio CD, higher sound out rates can make a distinctive difference in quality, especially in the upper tones and ranges.  However, for other bandwidth-intensive real-time processes such as the GeoPort Express Modem or PlainTalk Speech Recognition, you are required to return the Sound Out rate to 24.000 (AV) or 22.050 kHz (Power Mac).

Audio capture: performance and quality
Recordings from the PlainTalk microphone are not indicative of the sound-in capabilities, since the mic is uni-directional and monaural, optimized for speech recognition.  If you are not recording speech close up, you can get better results with a high-quality microphone combined with some method of preamplification to bring the mic signal up to line level.  One possible setup with a tape or DAT deck would be: microphone -> deck mic-in . . . deck line-out -> Mac audio-in.  This tip is courtesy of Ben Denckla (bdenckla@fas.harvard.edu).
With any microphone as the input source, be sure to eliminate feedback by turning off playthrough in the Sound control panel, or by jacking in a pair of headphones to the speaker port.
Recordings from other external decks are straight forward, as most models provide line out in one form or another.  For extended sound recordings, many of the video capture performance enhancing tips in the previous section also apply.

Audio capture: CD, DAT, and the digital domain
Versions of QuickTime since 1.6 can digitally convert audio CD data over the SCSI bus, bypassing the lossy A/D conversion stages to retain their original digital accuracy in full.  If you have any version of the AppleCD 300:
1) start any QuickTime aware application, even SimpleText
2) select Open from the File menu
3) navigate to the mounted Audio CD and select a track file
4) press Convert
5) press Options to change sampling parameters
Besides obvious copyright considerations, the user should be aware of the following two caveats.
Set the sample depth to 16-bit quality.  8-bit sound lacks enough fidelity to reproduce the native 16-bit quality for audio CD's.  You can expect audible hiss during playback of such samples, more so on superior speakers or a pair of headphones.  However, 16-bit sounds does take up twice as much space or more, since they are not supported by the venerable Macintosh Audio Compression and Expansion (MACE) routines.
Stereo sampling present a separate problem with QuickTime 1.6.x, where left and right audio channels are swapped at random.  Playback becomes especially intolerable through a pair of headphones.  QuickTime 2.0 fixed this important bug and also adds audio to AIFF support.
Users can also extract the encapsulated audio with either Movie2Snd (to System 7 sound file) or SoundTrack (to AIFF).
ftp://mirrors.aol.com/pub/mac/sound/soundutil/soundtrack.cpt.hqx
ftp://mirrors.aol.com/pub/info-mac/snd/util/movie-to-snd-113.hqx

With third-party CD-ROM drives, you need CD-ROM Toolkit (FWB, 415.474.8055) to enable QuickTime compatibility.  Independent of QuickTime, Disc-to-Disk (Optical Media, 800.347.2664) can convert from audio CD to AIFF, .snd, and .wav files.  For digital I/O such as DAT decks via SPDIF, inquire about the AudioMedia series of NuBus cards from Digidesign (800.333.2137, 415.688.0600, 415.327.0777/fax).

Sound editing and manipulation
For very basic sound cutting and pasting, you can simply adopt Fusion Recorder with its video turned off.  You will probably have to download the two QT to sound converters mentioned above for practical purposes.
If your needs call for 16-bit sound effects, note that Macromedia has released SoundEdit 16 to supersede SoundEdit Pro 1.0.5, which disabled all but the "backwards" effect with 16-bit sounds.
If you would prefer a shareware program, test drive the Sound Effects beta package.  It is still buggy, but shows plenty of promise.
ftp://mirrors.aol.com/pub/info-mac/snd/util/sound-effects-091.hqx

[AV] Professional quality audio mixing software
Michael Emery (memery@aol.com) once asked on MACAV-L:
Which 16-bit audio software should I acquire for mixing mono VOs and narration tracks, and stereo music tracks?
The reply from Craig O'Donnell (dadadata@world.std.com) was:
Your main requirements are a very large hard disk for your audio (600MB or larger) and, if you're going to back up the source files, a DAT backup (not an audio DAT).
As far as your other requirements, DigiTrax is pretty much the simplest thing going for that application. You could also look at Vision AV from Opcode, but Vision and Deck are both biased toward the MIDI musician who needs to sync MIDI music tracks to hard disk based audio tracks, (ie, MIDI instruments with a guitar and vocals overdubbed).
For version 1.0, DigiTrax is remarkably robust and although I have some quibbles with the interface, it is far less complex than Deck.
-- COD, author of "Cool Mac Sounds"
Both of these programs take advantage of the on-board DSP to provide multi-track recording and mixing.  Both are also being re-written for the Power Mac.  For Deck II information, call OSC at 800-343-3325, 415.252.0460.  For DigiTrax, contact Alaska Software at 800.500.3320, 408-738-3320, or AlaskaSoft@aol.com; a DigiTrax software demo is also available at:
ftp://mirrors.aol.com/pub/info-mac/snd/util/digi-trax-10-demo.hqx

GEOPORT & TELEPHONY
GeoPort: what is it?
By itself, the GeoPort is simply a new high speed serial port architecture, in theory capable of transmitting 4 megabits per second.  GeoPort devices sport mini DIN-9 connectors that are keyed so they cannot be inserted in normal DIN-8 serial ports.  The extra 9th pin provides power to the device, which usually supplies its own clock signal for higher transfer rates.
AV's contain one GeoPort, in place of the modem port; Power Macs have two.  So far, only two GeoPort devices exist: the GeoPort Telecom Adapter (analog telephone adapter pod) and the QuickTake 100 camera (which also has a plain serial interface), both from Apple.  Interestingly, Mac-the-Knive from MacWeek 2.6.95 briefly mentions the rumor of an "inexpensive" ISDN interface adapter that may appear later this year.
Normal serial devices, such as modems and printers, have no trouble with GeoPorts under most circumstances, though compatibility is an issue.  For hardware devices that fail, you need ASFU Fixer, an extension that installs the regular serial driver in place of the GeoPort one.  ASFU Fixer is a product of GDT Softworks, and has worked for GDT's PowerPrint, Software Toolworks' Miracle Piano, Video Director, and no doubt others as well.  Do not use this patch with GeoPort devices for obvious reasons.
ftp://ftp.csua.berkeley.edu/pub/jwang/geoport/asfu-fixer-101.hqx

GeoPort Telecom Adapter: know before you buy
The $125 adapter translates analog telephone signals to digital form and vice versa, using a 16-bit Singer audio codec and A/D/A converters on-board.  Digitized signals are then sent to and received from the 040-DSP combo or Power PC chip emulating the Express Modem.  The entire setup, when active, increases the System RAM usage by around 600K.  It also requires that the Sound Out rate be locked at 24.000 or 20.050 kHz for an AV or Power Mac.
Pod performance on a 660av or 840av is on par with a regular 14.4K modem, thanks to the separate DSP.  Download rates often reach 1600 cps for pre-compressed files, with either ZMODEM or SLIP/PPP FTP.  There is room for improvement with uploads and latency, however.  As for the DSP, an active modem connection sucks up nearly all of the real-time bandwidth, precluding concurrent Speech Recognition.
The Power Mac reaction to the adapter is less pleasant.  More bandwidth is indeed available with a Power PC processor, one 8100/80 was even shown running Speech Recognition with a 2400 modem connection in parallel.  However, both would hit the single main CPU resulting in a sluggish overall system.  Owners of the slower models have reported upwards of a 50% slow down and top out their transfer rates at a mere 1200 cps.
The pod package includes Express Modem, a control panel for the software modem; but no terminal programs, nor any SLIP/PPP/TCP software.  Buyers do get Express Fax, arguably the best (certainly the easiest to use) among the competition.

GeoPort Telecom Adapter: quality control
As publicized by MacWeek, a number of first generation GeoPort Telecom Adapters do not function reliably, caused by a separation of the EMI shielding from the pod chassis.  The afflicted adapters would produce a low buzzing sound when trying to dial, and are liable to cause random system crashes.
To check the hardware version of your GTA, look at the product identification label on the broad side of the pod.  The new models either bear a dark green/blue ink dot, or show part number 825-2362-B instead of 825-2362-A in the lower right hand corner.  Ignore the Canadian Communication Certificate and its registry number, you might actually need a magnifying glass for the extremely tiny model number.
If a pod displays the buzzing symptoms (hopefully, while still under warranty), ask firmly for a replacement from your dealer or 800.SOS.APPL.  Politely explain that Apple quietly acknowledges the problem, try another operator if necessary.

GeoPort Telecom Adapter: software updates
The physical adapter itself can be used with any GeoPort-equipped AV or Power Mac, provided that an appropriate GeoPort driver is present.  The latest GeoPort 2.0 software finally provides many of the telephony features promised at the AV introduction back in 1993.  There is also a revised 14.4k fax suite that is PowerTalk and QuickDraw GX friendly, plus built-in OCR support.
However, 28800 bps V.34 support is not provided with this update.  You can call Apple at 800.769.2775 x3127 to order the official upgrade kit.  For $8 plus $10 shipping and handling, you will receive the 4 floppy set of Express Modem, Fax, MegaPhone, and SITcomm Special Edition/GeoPort Telecom Adapter, and updated documentation in print.  All but the stripped down SITcomm terminal emulation software are also available online:
ftp://ftp.info.apple.com/Apple.Support.Area/Apple.Software.Updates/US/Macintosh/Networking.and.Communications/Apple.Telecom/

Express Modem: initialization strings
With the default modem compression (V.42bis) and error correction (V.42 LAP-M) protocols, AV GeoPort downloads often reach an excellent 1600 cps (characters per second).  However, uploading pre-compressed files with both options trips up an apparent bug in the modem software and nets anywhere between 800 to 1200 cps.  If the phone line is reasonably clean, the init string "AT&Q0" shuts both modem options off and yields a more respectable ~1400 cps both ways.
Power Mac GeoPort users find the V.42 4:1 compression algorithm far more taxing on their CPU than necessary.  For vastly improved transfer rates, try the init string "ATS48=128", which uses the alternative MNP 2:1 compression protocol.

Express Modem: application compatibility
Several users could not, initially, get terminal emulators (ZTerm being the most frequent example) to acknowledge the Express Modem.  Here are some simple tips to try with your program:
With ZTerm, which has a problem with extended progress result codes on all modems, add "W0" to your init string to disable the "CARRIER nnnnn" message that confuses the auto-dialer expecting "CONNECT" instead.
Leave hardware handshaking and other gobbledygook options turned off, the Express Modem handles many traditional modem headaches behind the user's back.
America Online users experiencing consistent line drops should upgrade their connection program to version 2.1 or later for full 9600 compatibility.  Prodigy users should upgrade to 9.67.05 or later.
On the other hand, software that uses the Communication ToolBox (CTB) will have no trouble with the included Express Modem tool.  Similarly, SLIP/PPP packages that support standard CCL dialing scripts can use the Express Modem 14400 or any Hayes compatible modem script.
With TIA (The Internet Adapter), you have to dial, connect, and launch TIA all through an InterSLIP gateway script.  Bill Arnett (billa@netcom.com) provides working samples available for you to customize.  The standard method of dialing with a terminal program won't work since the Express Modem drops the carrier every time the connect tool or program is closed.  There is also no way to hold a connection in place between restarts.
ftp://seds.lpl.arizona.edu/html/billa/tia/
http://seds.lpl.arizona.edu/billa/tia/faq.html

Telephony: where are more tools?
Cypress Research seems to have something for any GeoPort home office, offering full featured MegaPhone, PhonePro, and Voice Messenger with special pricing for those with the Apple Telecom 2.0 kit.
Also announced but not yet available is MUSI's TeleNavigator, advertised as an all-in-one package that can handle your e-mail as well as your voice-mail.
ftp://ftp.csua.berkeley.edu/pub/jwang/geoport/telenavigator-pr.txt

PLAINTALK TECHNOLOGIES
Terminology and overview
PlainTalk refers to the concept of natural spoken language communication with the computer, including both Speech Recognition (SR) and Text-to-Speech (TTS).
The SR "engine" consists of the extensions Speech Recognition, SR Monitor, control panel Speech Setup, plus assistance from AppleScript.  SR only works on AV and Power Macs due to the real-time processing power requirements, but it does not work on 68040 Macs with the Power PC PDS upgrade card due to the lack of 16-bit audio input.
The TTS "engine" consists of the extension Speech Manager, with speech synthesizer components MacinTalk 2, MacinTalk 3, and MacinTalk Pro.  The requirements of TTS vary greatly depending on the synthesizer you use, from a Mac Plus running System 6.0.7 (minimum MacinTalk 2), to a 68040 running 7.1 (highly recommended for MacinTalk 3).  Exact synthesizer requirements are discussed a few headings below.
As you can see, there is plenty of room for confusion with a slew of names for concepts, files, and components.  Please explicitly use the following names when discussing PlainTalk in the correct context:

AppleScript v1.0, 1.1 (current)
	High level System scripting language under OSA (the Open Scripting Architecture), required by Speech Recognition.  AppleScript 1.1 has the Apple Event Manager rolled in, was a separate extension under 1.0.
MacinTalk 2 v1.1.1, 1.2.1 (current)
	Low-quality speech synthesizer.  v1.1.1 built-in to Speech Manager 1.1.1.  Standalone file v1.2.1 optional with Speech Manager 1.2.1 and 1.3.
MacinTalk 3 v1.2.1, 1.3 (current)
	Special-effects speech synthesizer.  Built-in to Speech Manager 1.2.1 and 1.3.  Does not exist as a standalone file.
MacinTalk Pro v1.2.1, 1.3 (current)
	Natural language speech synthesizer.  Both versions are standalone files, optional under Speech Manager 1.2.1 and 1.3.
PlainTalk Text-to-Speech v1.0 (obsolete)
	Extension found only with PlainTalk 1.0 (660av and 840av).  Forerunner to Speech Manager with an all-in-one design containing MacinTalk 2 v1.0 and MacinTalk Pro v1.0, plus the Female Compressed voice.
Speech Manager v1.1.1, 1.2.1, 1.3 (current)
	Basic extension required for TTS.  Controls voices and synthesizers.
Speech Recognition v1.0, 1.2.1, 1.3 (current)
	Basic "recognition" extension required for SR.
SR Monitor v1.0, 1.2.1, 1.3 (current)
	Background-only "listening" application launched as SR activates.

Speech Recognition: performance, quality, and limits
PlainTalk Speech Recognition is a speaker-independent, connected-speech, environmentally adaptive system.  SR can be used to complete dialog boxes, select pronounceable menu items, and execute user-defined aliases and macros.  SR does not perform dictation (speech-to-text).  For this capability, you should seek out a product called PowerSecretary from Articulate Systems.
Realistically, 16MB of physical memory is required to run any modern applications with SR, which reserves 2.5MB without, or up to 5MB with speech feedback.  On a DSP-equipped 660av or 840av, active SR imposes negligible performance penalty to the main CPU, while a Power Mac is slowed down by approximately 10-15%.  The recognition rate ranges from mediocre to excellent, depending on the speaker and the surrounding environment.  You will likely find the optimal tolerance setting for the best "hit rate" after a short time of practice in a quiet room.

Speech Recognition: versions and updates
North American editions of the 660av and 840av are pre-installed with PlainTalk 1.0 software.  SR 1.0 was written specifically for the DSP, and did not work on Power Macs.  PlainTalk 1.2 was introduced later with a Power Mac-only SR 1.2.  Only the Power AV systems actually ship with the software and microphone.
The latest PlainTalk 1.3 has been released to take advantage of System 7.5.  This version can be used with all 660av, 840av, and Power Macs.  Certain aspects of SR 1.3 do require System 7.5, including Apple Guide help and new "smart" Speakable Items aliases that query the scriptable 7.5 Finder for their targets.  If you install SR 1.3 over Finder 7.1 and try to execute a Speakable Item, it will cause AppleScript time-out errors but no real harm.  Hand-linked aliases to the Apple Menu Items are not affected, however.
ftp://ftp.info.apple.com/Apple.Support.Area/Apple.Software.Updates/US/Macintosh/System.Software/PlainTalk.1.3/

Text-to-Speech: synthesizers and requirements
The PlainTalk Text-to-Speech file organization has changed greatly since the AV introduction.  The current file layout consists of Speech Manager with the MacinTalk 3 synthesizer built-in, and optionally MacinTalk 2 and MacinTalk Pro.  With up to three different synthesizers installed, Speech Manager automatically invokes the one associated with the particular voice chosen.

MacinTalk 2
Voices: Marvin (built-in), Brenda et al (all in MacinTalk 2 Voices)
Only synthesizer that works on a Mac Plus with System 6.0.7 and on up
Intended for low quality speech, with limited capabilities to convert abbreviations and number strings to text
Small 150K memory footprint,  approximately 30K disk space per voice
v1.1.1 built into Speech Manager 1.1.1; v1.2.1 optional with 1.2.1 and 1.3

MacinTalk 3
Voices: Fred (built-in), Albert et al (separate small voice files)
68030 or better, System 7.1 required
Most CPU-intensive (fancier pitch control), you may experience choppy or stuttering speech on anything less than a 68040
Provides special effects voices (laughing, sing-song, underwater)
Built into Speech Manager 1.2.1 and 1.3; not available earlier

MacinTalk Pro
Voices: Victoria, Bruce, Agnes (large files with distinctive "lips" icons)
68020 or better, System 7.0 or better required
Most resource hungry, 700K-2.6MB RAM, 300K-2MB disk space per voice
Most human and natural sounding, highly intelligible speech output with extended text processing rules (32 digit long numbers, for example).
Optional component under Speech Manager 1.2.1 and 1.3

Text-to-Speech: versions and updates
PlainTalk 1.3 installs Speech Manager 1.3, AV and Power Mac owners should see the Speech Recognition section above for upgrade details.  For folks not interested or not capable of SR, a functionally equivalent Speech Manager 1.2.1 is available separately.  This directory also stores MacinTalk 2 v1.2,1, MacinTalk 2 v1.2.1 voices, MacinTalk Pro v1.2.1, MacinTalk Pro v1.2.1 voices (each in small, normal, and high quality varieties), and the complete set of MacinTalk 3 v1.2.1 voices:
ftp://ftp.info.apple.com/Apple.Support.Area/Apple.Software.Updates/US/Macintosh/System.Software/Text-to-Speech.Software/

If you are upgrading from PlainTalk 1.0 or Speech Manager 1.1.1, note that voices must now reside in a new Voices folder inside Extensions.  Move the following pieces manually to their new location:
MacinTalk Voices 1.1.1 (you can update to 1.2)           -> Trash
PlainTalk Text-to-Speech 1.0                             -> Trash
Speech Manager 1.1.1                                     -> Trash
TTS Female voice 1.0                -> Extensions:Voices or Trash
TTS Male voice 1.0                  -> Extensions:Voices or Trash
TTS Male voice, Compressed 1.0      -> Extensions:Voices or Trash

The three Female and Male voices listed at the bottom will work in the new location, the compressed Female voice cannot be salvaged as it was actually embedded in the PlainTalk Text-to-Speech extension.  However, you may soon find that even normal flavors of Victoria and Bruce offer more quality using less memory and disk space.

Text-to-Speech: miscellaneous tidbits
Besides TeachText 7.2 and SimpleText, there a number of Speech Manager aware applications.  Dr. Joe Campbell (jpcampb@afterlife.ncsc.mil) used to maintain such a list, the somewhat outdated March 94 edition is at:
ftp://mirrors.aol.com/pub/info-mac/info/sft/speech-manager-apps-94-03-28.txt

Able to modify the pronunciation dictionaries used by Speech Manager programs, DictionaryEdit is a shareware written by Simon Fraser (s.fraser@ic.ac.uk):
ftp://mirrors.aol.com/pub/info-mac/cfg/dictionary-edit-12.hqx

To set the default reading voice with applications such as SimpleText, there is Robert Geisler's (geisler@zappa.mpib-tuebingen.mpg.de) freeware:
ftp://mirrors.aol.com/pub/info-mac/snd/util/voices-11.hqx

With MacinTalk Pro voices, you can save spoken speech to disk as System 7 sound files through examples given in the HyperCard stack by Lawrence D'Oliveriro (ldo@waikato.ac.nz):
ftp://mirrors.aol.com/pub/info-mac/card/speech-manager-ext.hqx

For international voices, Jean-Claude Maurel (jc@infovox.se) of Telia sent me the following data sheet information:
The synthesis system is multi-lingual and currently comprises the following 10 languages: American and British English, French, German, Italian, Spanish, Swedish, Norwegian, Finnish and Icelandic. The synthesizer has 5 different voices for each language and in addition the user can change pitch, aspiration and intonation. The user can also create a user lexicon to store the pronunciation of words that do not conform to the usual pronunciation rules of the language, for instance proper names, abbreviations etc.
----------------------------------------------------------------------
Telia Promotor Infovox AB, Box 2069, S-17102 SOLNA, Sweden
Tel: +46 (0)8 764-35-11, Fax: +46 (0)8 735-78-76, e-mail:jc@infovox.se
----------------------------------------------------------------------

MISCELLANEOUS
Easter eggs
The North American (non-localized) edition of the 660av and 840av CD InstallMeFirst has an invisible QuickTime movie called "Our Gang!" hidden in the Preferences folder.  Open your favorite movie player and use the standard File Open dialog to view the file since you cannot detect it on the desktop.
There are also a couple of pictures of the develop team tucked away in the ROM, which have been extracted and archived for your convenience.
ftp://mirrors.aol.com/pub/info-mac/grf/av-rom-images-jpeg.hqx

Two rather unique hardware error sounds were stashed in AV and Power Mac systems.  Restart your Mac and press the interrupt button (or command-power) immediately after you hear the startup chord.
The vaunted PlainTalk Speech Recognition (develop code name: Casper) Easter eggs are hidden within the version 1.2 System Speech Rules file, archived along with full instructions at:
ftp://ftp.csua.berkeley.edu/pub/jwang/plaintalk/plaintalk-easter-eggs.hqx

FAQ and file updates
This FAQ and many AV-related files are available via FTP and the World Wide Web:
ftp://ftp.csua.berkeley.edu/pub/jwang/
http://www.csua.berkeley.edu/~jwang/AV/

Internet users may finger a special service to check for new additions for FTP, returning a detailed and recursive directory list of all files available:
finger jwang.av-dir@ocf.berkeley.edu | more

Folks without ftp access are welcome to test my e-mail file request server.  For instructions, send a message to jwang@csua.berkeley.edu with the word "request" in the Subject: header, and the word "help" on a line by itself in the body.  This server only has access to the files in my directory.  For files at the other ftp sites, please send mail to bitftp@pucc.bitnet (BITNET only) or ftpmail@decwrl.dec.com with the word "help" in the mail body for more information.
For faster access from Japan or the Pacific Rim, there is a comprehensive ftp service maintained by Hiroyuki Takahashi (hiro@cent.saitama-u.ac.jp), containing an exhaustive collection of AV related documents, patches, and applications, including an on-going translation of the FAQ to Japanese.
ftp://ftp.cent.saitama-u.ac.jp/pub/mnt5/mac/av/

For non-Internet surfers, current versions of the FAQ should be mirrored at the following on-line services (let me know if you upload to others):
America Online, thanks to hiramw@aol.com
BMUG and affiliates, thanks to Mark Schrier (schrier@garnet.berkeley.edu)
OneNet (FirstClass), thanks to Tyson B. Bouncher (boucher@mail.cs.orst.edu)
Ziff/Net, thanks to Craig O'Donnell (dadadata@world.std.com)

MACAV-L mailing list
Bill Higgins (higgins@fnal.fnal.gov) brought to my attention the MacAV-L mailing list.  To subscribe to MacAV-L, send the following command in the mail body to LISTSERV@UAFSYSB on BITNET or LISTSERV@UAFSYSB.UARK.EDU on the Internet:
SUB MACAV-L your.firstname your.lastname

Once subscribed, if you only want the daily digests (one long e-mail message instead of many short ones), send the following command to the above LISTSERV address at any time (note the plural case of DIGESTS):
SET MACAV-L DIGESTS

To unsubscribe, send yet one more command to the LISTSERV address (important: a number of people end up looking silly by sending SIGNOFF commands to the actual mailing list instead of the LISTSERV processor, of course you won't be one of them.)
SIGNOFF MACAV-L

LEGAL DEPARTMENT
Copyright
The Macintosh AV FAQ is copyright 1993-95 by the author, James Wang (jwang@csua.berkeley.edu).  Readers are encouraged to electronically channel copies of this file to BBS's and other on-line services, provided that the document is left unmodified and it does not cost potential downloaders more than the basic connection fee.  Quoting from the FAQ is equally welcome, given proper attribution to the author and any contributing writers.  All other forms of duplication, distribution, and transmission without the author's prior consent are forbidden.
Disclaimer
Complete veracity of the information herein is not guaranteed, and they are subject to change at any time, "without prior notice."  In particular, the author cannot be held responsible for any hardware damage or data loss that readers incur as a result of reading this FAQ.  All product titles cited remain trademarks of their respective holders, and in no way constitute any kind of endorsement.

Thank you's (in no particular order)
Noah Price (noah@apple.com), for answering the questions long before I got to play with my 660av, and for being a continued source of information and help.
Chris Kim A (kima@netcom.com), the wonderful HTMLization of this document and for sprucing it up with original graphics.  His electronic-portfolio is at:
ftp://ftp.netcom.com/pub/kima/

Ben Denckla (bdenckla@fas.harvard.edu), for authoring first the DSP FAQ and now the AV and Power Mac Audio document.
Ralph Novy (ralph@studsys.mscs.mu.edu), for his suggestions on the PlainTalk section and copy-reading its draft.
Philippe.Astier@scinfo.u-nancy.fr, for proof reading everything while translating the FAQ to French.
Irene Bensinger (lirene@aol.com), for many "software" contribution from Japan.
John Spady (jspady@teleport.com), who sent me rtftohtml three months ago, which I have yet to master.
The mirror team, for getting the FAQ beyond the Internet frontier.
Everyone I attributed herein, for contributions, tips, and information.
Everyone that I didn't, for all those nameless net wisdoms.