Re: CD ROM Capacity?

Ben Waggoner (ben@journeyman.com)
Mon, 26 Oct 1998 10:52:43 -0700

Bart McLaughlin asked:
> I'm a pretty experienced video producer/editor, and I've just gotten a gig
> to produce an archival CD ROM. The client has about 6 hours of VHS video
> he'd like digitized to CD, with accompanying text and simple graphics. I'm
> thinking 160x120 AVI video, 16 bit 22K sound, running in a window on the
> right. Text and graphics to the left, all set up in Director. My question:
> how much of this kind of program will fit on a CD? I have no idea how big
> my AVI files will be. If you can recommend a good source book (or web site)
> for this kind of tech info, I'd really appreciate it. Thanks -

Hello,

If you all may indulge me a bit of math, given your six hours of video,
and assuming you've got roughly 600 MB left on your disk after programs,
etc, we're talking about... 28K/sec. You'll have a lot of trouble doing
that in AVI. Assuming 16-bit 22KHz mono audio with IMA compression,
that'll take up 11 K/sec, leaving only 17 for video. If you can target
Win32 only, and the content isn't too complex, Indeo 5.06 with a long
keyframe rate might be able to pull that off with okay quality at 15fps
or so. Better quality can be gained by setting a quality, and letting
the data rate range with content, but finding the right Q value to
optimally fill your bit budget will require extensive trial and error.
If you are targeting pre Win32, you'll have to either use the not nearly
as good Indeo 4.1, or Cinepak.

You'll find far better results with QuickTime, using the Sorenson video
codec, and either the QDesign Music (for music) or PureVoice (for voice)
audio codecs. Free versions are built into the basic package, which do
a more than adequate job. And if you're very quality concious and have
a Mac, get Media Cleaner Pro and Sorenson Pro. Together they use a
Variable Bit Rate compression techinque, where you request a average
data rate, specify a peak, and it determines how to best allocate
bandwidth throughout the clip for the highest and most consistent
qualilty. It rocks hard.

So, in that environment, you could spend 4Kbytes/sec on 44.1 mono
QDesign, using the remaining 24 K/sec for video. Assuming talking-head
style content, Sorenson could happily give you a 240x180 window instead
of 160x120, and probably at a full 30fps.

If you are commited to Win 3.1 playback, and so have to use VfW or QT
2.1.2, you should know that the EXACT same data will yield smaller files
with QuickTime, since AVI uses a very inefficent block padding system.
The smaller the total data rate, the larger the AVI would be relative to
the MOV.

If you haven't seen my codec review from DV, check it out for free at:

http://www.dv.com/magazine/1998/0698/compression.pdf

With samples, starring goofy me at:

http://www.dv.com/magazine/1998/0698/0698compress.html

Ben Waggoner
Journeyman | CTI Group