Amiga Plus 2002 #11/Amiga Plus CD - 2002 - No. 11.iso/Sound/EasyACDDA/Docs/CDDA.doc

Text File | 2002-10-28 | 7KB | 149 lines

Short: play and save digital audio
Type: disk/cdrom
Uploader: [e-mail]
Author: [e-mail]

Read audio data from a CD-DA disk (normal audio CDs) and play back
via audio.device (22kHz) and store to outputfile either in 16bit, stereo,
44.1kHz AIFF or in 8bit, mono or stereo, 22.05kHz 8SVX.

usage:

cdda START,LENGTH,TRACK/N,VOL=VOLUME/N,FILE,8SVX/S,MAUD/S,WAV/S,16BIT/S,
     MONO/S,MUTE/S,LIST/S,DEBUG/S,BUFS/N,QLEN/N,PLAN,TMP,NOFILTER/S:

START  = startblock
LENGTH = number of blocks
TRACK  = start relativ to track number
VOL    = volume in percent (0..800)
FILE   = file to save to
8SVX   = use 8SVX format instead of AIFF
MAUD   = use MAUD format instead of AIFF
WAV    = use WAV format instead of AIFF (disables audio)
16BIT  = experimental high resolution mode for audio output
MONO   = map stereo to single channel and write mono 8SVX
MUTE   = disable audio output completely
LIST   = show table of contents
DEBUG  = print lots of debugging info through debug.lib (use sushi!)
BUFS   = number of CD blocks to do in a single read.. default is 8.
QLEN   = length of CD-ROM input queue, default is 16.
PLAN   = method to access the CD-ROM, current plans are 'a','b' and 'c'
         'a' is for Sony CDU 8003 and compatible
         'b' is for Toshiba XM3401TA and compatible
         'c' is for NEC 2X and 3X
         'd' is for some Grundig CD-ROMs, may work on Toshiba drives
         'e' is for ATAPI (standard command)
         'f' is for ATAPI (pre-standard command, never seen such a drive)
         the program detects some drives itself but you can force it
         to use a specific plan with that option
TMP    = temporary file to store second channel in 8SVX mode.
NOFILTER = when downsampling to 22kHz audio, don't filter. Reduces CPU
           usage a little.

You can use the environment variables CDDA_DEVICE and CDDA_UNIT to choose
something else than the default ("scsi.device" and 2).

To accomodate for older device drivers you can ask for a specific memory type
used for all SCSI-direct buffers. This is done with the environment variable
CDDA_BUFMEMTYPE. A value of 2 asks for chip memory, a value of 512 asks for
memory reachable by Zorro-2 DMA controllers. Even for controllers that do
not need a specific memory type it might show better performance.

There's a tiny program called 'led' in the archive which toggles the
audio lowpass filter on newer machines. Disabling the lowpass filter
will usually get better audio quality but may cause aliasing distortion
depending on the bandwidth of your speakers.

Version 1.11 and newer of this program no longer saves data in RAW format.
Instead it writes an AIFF header so that other programs can easily identify the
data. If you select the 8SVX switch then cdda will write in IFF 8SVX format
instead.

Version 1.24 and newer can also write the MAUD format used by software for
the Toccata 16bit audio card.

8SVX output is affected by the VOL and MONO setting so that you can scale
the output for maximum dynamic range within the 8 bits of 8SVX, you can also
select either mono or stereo output. 8SVX samples are reduced to a sample rate
of 22050Hz for easy play back with any Amiga 8SVX player. Actually you get
exactly what you hear from cdda.

Neither AIFF, MAUD nor WAV output is affected by these settings, they always
save the full 16bit data.

Saving in 8SVX stereo has a slight problem since 8SVX saves each channel in
a contigous part of the file. cdda will alternate between both channels which
causes lots of head movement and is therefore much slower.. usually too slow
for a smooth audio output. I suggest to MUTE audio when saving 8SVX stereo
files.

Another point. Seeking in large files requires reading of 'extension blocks'
which point to the actual data. There can be lots of extension blocks for
large files which are best cached in RAM with the ADDBUFFERS command. The
typical 30Megabyte file for a song needs about 900 buffers on partitions
with 512 byte per block. Another solution is to create a harddisk partition
with larger blocks (possible with the ROM filesystem from AmigaOS 3.1)
which can reduce the need for extension blocks a lot (with 2048 byte/block
you just need 36 extension blocks for the 30Megabyte file).

If you have 2 disks or a large RAM disk you can use the TMP option to
circumvent the problems with stereo 8SVX. cdda will store the data from
the right channel into the file passed with the TMP option. When all data
has been recorded it will append this data to the real output file and delete
the temporary afterwards. If you put the TMP file on the same physical disk
as the output file this might result in even heavier disk activity than when
using a single file, it saves you from having tons of buffers though since
no seeking is done within a file.

Version 1.37 supports the NEC 3X (and possibly NEC 2X) CD-ROM drives which
have two problems.

First, any command send to the drive while reading audio data disrupts the
data stream _without any notice or error condition_. Then audio data is
definitely lost, and if an odd number of bytes is lost the byte order of the
data gets changed and the result is lots noise. I haven't found any possibility
to detect such a condition or to prevent other programs from sending commands.
Unfortunately this also includes most CD-ROM filesystems or SCSI drivers that
poll the unit for disk changes.

Second, the NEC 3X does not disconnect from the bus while reading audio data
(it does normally when reading CD-ROM disks). That's why this version of cdda
allows finer control of the queuing parameters. Previously you could
set the size of the I/O buffers with the BUFS parameter (in units of CDDA
blocks). Now you can also change the length of the input queue which is
the number of I/O buffers used for the CD-ROM. The total buffer size is
therefore BUFS * QLEN * 2352 Bytes or BUFS * QLEN / 75 seconds. Small buffers
improve throughput on the SCSI bus (the NEC 3X doesn't like BUFS=1 though)
but increase CPU load.

Version 1.40 fixes a few bugs in 1.37.

Version 1.50 adds some compatibility code. It also fixes the problem
with reading the end of the CD. The reader code always tried to read
BUFS blocks even when this extended the read beyond the end of the
disk. This results in "No more data" messages on drives that do
not return partial blocks in this case.

Version 1.51 handles the "no seek complete" message.

Version 1.53 detects Pioneer DR-* and DRM* CD-ROM as compatible with PLAN a.

Version 1.54 recompile with latest SAS/C

Version 1.55 experimental code for IDE drives and drivers that send ATAPI
commands transparently (PLAN e and f for ATAPI and a former proprietary
command). A test with IDEfix crashes the machine though.

Version 1.57 fixed a bug in ATAPI support, now plays a few seconds and then
crashes. Could be an Idefix bug.

Version 1.60 added WAV file output, this will automatically mute audio
because the data isn't byteswapped for WAV (the audio routines need
bytes swapping).

Version 1.64 enabled BUFS for ATAPI. Seems to work stable together with
atapi.device 118.3 and idefix.library 99.1.

Michael van Elst