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%% Video Capture by Douglas J. Nakakihara %%
%% dnakakihara@bix.com %%
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NOTICE: This is the originally submitted text for an article that
appeared in the September 6, 1993 issue (#113) of MICROTIMES magazine.
(There are some slight edited differences between the published
version and this one.)
This article is freely-distributable as long as it remains unchanged
and this notice and the copyright remain included.
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or similar media, including those electronically distributed,
without obtaining prior approval from the author. This provision
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Specific permission has been granted to Amiga Report.
Copyright(C)1993 Douglas J. Nakakihara.
The author can be reached thru Internet at dnakakihara@bix.com.
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30fps Video Capture and Non-linear Digital Editing
By Douglas J. Nakakihara
There are a lot of people who believe that capturing moving video
on a desktop PC is a fairly easy thing to do. Just install a video
capturing board in your PC, connect the thing to your video source, and
click the record button. Just like a VCR, right? Well, not quite.
The problem lies in data transfer rates. Depending on file
format, a single full-frame of video is at least one-half megabyte in
size. So one second of video is about 15MB of data. A PC normally
can't transfer that much data to a hard drive that quickly. Saving the
data to RAM is an alternative, but cost prohibitive for anything more
than a few seconds. To compensate, most boards capture less than a
full-frame of video. Until some sort of hardware compression like JPEG
becomes affordable, for the average desktop videographer, capturing
full-frame video at 30fps may seem to be just a dream.
The VLab
Well Toto, we're not in Kansas anymore. MacroSystemUS's VLab card
for the Commodore Amiga can do 30fps full-frame video capture. Perhaps
even more astonishing is that fact that you can even use a cheap
consumer grade VCR as your video source. Have I piqued your interest
yet?
VLab accomplishes this amazing feat using their innovative
Interleaved Frame Recording (IFR) technique. Basically the VLab
captures frames as fast as your Amiga can do it. By making multiple
passes at the video source, VLab automatically captures more and more
frames. For example, on the first pass it might capture frames 1, 16,
31,... The second time around, it might pick up frames 2, 17, 32,...
As you can see, ultimately, all 30 frames for each second can be
captured! In this example, it would take 15 passes to capture all of
the frames. Obviously, this will only work for video on tape or
laserdisc. (Be kinda hard to rewind live video!)
The secret to IFR is the selection of a Keyframe, which provides
VLab with a point of reference on your video source. Once the Keyframe
has been identified, VLab only needs to know how many seconds after the
Keyframe it should wait before capturing frames. When VLab is capturing
frames, it knows based on time which frames it needs to capture--
accuracy to a thirtieth of a second is child's play for a computer. A
Keyframe seems to occur whenever there is an abrupt change in the video
signal, like when the camera cuts to a different location or to a close
up of an actor.
The IFR process basically works like this. First you put your VCR
in play mode and click on VLab's Find Keyframe button. VLab will let
you know when a Keyframe is found, which must precede the start of your
scene. (If it isn't simply start a little farther back on the tape and
try again.) As soon as your scene comes up, click on the Start Scene
button. Now all you need to do is click the Start button, rewind the
tape past the Keyframe, and play the tape again. Each time VLab
finishes a pass of capturing frames, you must rewind and play the tape
again.
The total number of captured frames is selectable by the user. If
you're capturing at 30fps, just multiply the length of your scene in
seconds by 30. To improve capturing speed and decrease storage
requirements, you can reduce the capture resolution or capture in black-
and-white. When doing IFR, make sure you disable your screen saver as
it may throw VLab's timing off and cause the wrong frames to be
captured.
Look Ma, No Hands
There are also provisions for automating the rewinding process. I
highly recommend a terrific product called AirLink by Geodesic Designs.
This is an inexpensive infrared (IR) universal remote control for the
Amiga. Example ARexx scripts to control AirLink are already included
with the VLab software. AirLink can automatically rewind your tape past
the Keyframe and then put your VCR back into the play mode, at the end
of each IFR pass! Essentially, once you've set up the IFR parameters,
you can click a button and walk away. AirLink will also work with
camcorders, laserdiscs, etc., as long as they can be controlled with an
IR remote.
Storage Requirements
You're going to need a large hard disk to store all of the frames
you capture. Although IFR initially saves frames in a compact YUV
format, at 30fps, the storage requirements can really add up. I am
hoping that a provision to convert the captured images to a smaller file
format after each IFR pass, thus reducing overall storage requirements,
will be added in the future.
For the average user, 30fps may be overkill. The storage
requirements alone may discourage its use. A more manageable frame rate
is 15fps. Obviously, motion will not be as smooth as it is at 30fps,
but it's not annoying.
Other Features
In addition to IFR, VLab will also capture a sequence of frames at
up to 6fps. This is sort of like making a single IFR pass at a video
source. However, the sequence-capture has a little more control over
what is captured. A nice feature is that you have the option of using a
resolution of one-half, a third, or a quarter of the screen. This can
significantly reduce storage requirements. Obviously, VLab won't even
break a sweat capturing a single frame of video. Individual frames can
be saved in any Amiga format including 24-bit IFF and AGA.
VLab has loads of other features including extensive ARexx
support. You can also monitor the incoming video source in greyscale in
a movable window. Video played fairly smoothly in this window on my
A3000. You can't see much detail, so depending on your needs you might
want to use a signal splitter and watch the video source on a separate
monitor. Real time color, contrast, luminance, and gamma controls as
well as luminance, chromanance, and noise filters.
VLab fits into any Zorro II/III slot and does not require the
video slot. The VLab Y/C version includes two RCA video inputs plus a
Y/C connector for Hi-8 and SVHS video sources. Inputs are software
selectable. An external version is available for the A500, A600, and
A1200.
Now What Do I Do?
Applications for the VLab are only limited by your imagination.
For example, most desktop video users are limited to morphing--the
current "hot" video effect--one static image to another. With VLab you
can now generate the images needed for moving morphs (i.e., the source
and target images are moving). Examples of moving morphs can be seen in
the movie Terminator 2 and Michael Jackson's Black or White music video.
For the 3D rendering people, how about the ability to wrap moving video
onto your objects! Computer-aided presentations could include video
segments without the need for VCRs or laserdiscs. Vlab could provide
source images for rotoscoping (painting on frames by hand). A non-
linear digital editing system could also be designed around VLab.
Bottom line: the ability to affordably capture video at 30fps is going
to open whole new worlds to desktop video.
The VLab-Retina Team
When the VLab is teamed with MacroSystemUS's Retina display card,
VLab's features are enhanced. The video source can be monitored on a
Retina display in 16-bit color. There is a noticeable delay in the
display update, but it does give you a better idea of what will
ultimately be captured. Also, Retina comes with a program called
Makerace that will compile the captured images with sound into an
animation playable on the Retina. With a VGA video encoder, it should
be a fairly simple operation to get the Retina output to videotape. On
my Amiga 3000, I was able to play a 320 x 200 animation with sound using
a 16-bit display at about 15fps. For even faster playback, read on!
A Match Made in Heaven
MovieMaker ($895 list) from Interactive Video Systems is a non-
linear digital video and audio editing system that comes with its own
16-bit stereo sound card. MovieMaker provides a way to arrange and play
VLab-captured frames full-screen at 30fps, with 16-bit sound to boot!
MovieMaker works very nicely in an Amiga 3000 and should work better in
an Amiga 4000, if it has a Zorro III SCSI controller (currently a rare
species). MovieMaker operates best with certain hard drive models so
IVS also offers it bundled with an approved hard drive.
Using VLab's IFR, I captured several seconds of video. I also
digitized the audio using AES, the audio software that comes with
MovieMaker. Then using ADPro, I converted the captured YUV images to
DCTV format. Incidentally, ASDG's product ProControl, a front-end for
ADPro, made this a very easy task and saved me the trouble of writing my
own ARexx script. Next I imported the DCTV files into the MovieMaker
hard disk partition. (MovieMaker requires its own partition.) It took
a couple of tries to get the audio synced properly, but the resulting
playback was incredible!
Using MovieMaker's wordprocessor-like editing functions, I was
able to manipulate my captured video in nearly unlimited fashion. Max
Headroom stutter effects were easy as pie to do. This VLab-MovieMaker-
DCTV setup seems like a natural for doing MTV-style music videos.
Although MovieMaker's output is not broadcast-quality, it is more
than adequate for home and industrial use. MovieMaker would also be
valuable in a professional pre-production environment. Quick rendered
3-D animations could be edited and tested with an audio track before
being rendered in broadcast-quality form. Also, storyboarding would be
a breeze with MovieMaker using either static or animated sequences.
MovieMaker needs about 100MB per minute of playback. I would
estimate that for serious work, you'll need at least a 1GB hard drive.
Remember, the original source files have to also exist before they are
transferred to the MovieMaker partition. Fortunately, 1GB drives have
becoming somewhat affordable lately. Note that MovieMaker does not
require you to dedicate the entire drive, it only needs a partition.
That's A Wrap
At current street prices, a VLab-AirLink-MovieMaker-DCTV package
will cost you around $1,500. If you need a hard drive, you'll have to
add that into the cost too. This may sound expensive, but I am not
aware of anything on any computer platform that will match the
performance and flexibility of this set up--at least in this price
range.
AirLink
I just couldn't end this article without mentioning a little bit
more about AirLink. By itself, this is an awesome device. It acts as a
programmable universal IR remote. All you do is draw a picture of your
remote using any paint program (you only need to include the functions
you will use). Then you point your remote at the AirLink device, which
plugs into the joystick port, and record the IR signals one at a time.
Each recorded signal can be associated with any button in your picture.
The AirLink's IR LED can be triggered by your mouse, ARexx, user-
defined hot keys, serial and parallel port data, and MIDI events. With
AirLink, all IR-remote-controlled devices, like laserdiscs, TVs, VCRs,
Stereos, CD players, etc. can be at your beckoned call. You will no
longer be limited to controlling only those devices that have serial
port access. AirLink is perfect for multimedia presentations.
You can even trigger other events beside IR, including sending
data out the MIDI, serial and parallel ports, executing ARexx commands,
emulating keystrokes and mouse clicks, and executing programs. It is
also possible to add eight additional IR LEDs using an adapter connected
to the parallel port! An upcoming version of the software will allow
you to open an AirLink control window on any public screen. With this,
you can control your VCR and be doing VLab operations, all from the same
screen!
VLab Y/C
$599.95
VLab
$499.95
VLab External
$549.95
MacroSystemUS
17019 Smugglers Cove
Mt. Clemens, MI 48038
(313)263-0095
AirLink
$50
Geodesic Designs
P.O. Box 956068
Duluth, GA 30136
(404)822-0566
MovieMaker
$895
Interactive Video Systems
14804 Beach Blvd.
La Mirada, CA 90638
(714)228-2040
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