Path: utzoo!attcan!uunet!samsung!gem.mps.ohio-state.edu!tut.cis.ohio-state.edu!att!watmath!watcgl!imax!dave
From: dave@imax.uucp (Dave Martindale)
Newsgroups: comp.graphics
Subject: Re: Re: Workstations that can record/play realtime video
Message-ID: <1989Nov16.144002.234@imax.uucp>
Date: 16 Nov 89 14:40:02 GMT
References: <6509@portia.Stanford.EDU> <1360003@hpspcoi.HP.COM> <6640@portia.Stanford.EDU>
Reply-To: dave@imax.UUCP (Dave Martindale)
Organization: Imax Systems Corporation, Oakville Ontario
Lines: 18

In article <6640@portia.Stanford.EDU> rick@hanauma.UUCP (Richard Ottolini) writes:

>NTSC is rated at 3.5 MHz or 32 GB / hour given 2bits per Hertz, the
>minimum encoding under Nyquist limit.

The NTSC bandwidth is 4.2 MHz.  Nyquist says your sample *rate* has to be
twice that; 2 samples per Hz.  However, sampling theorem assumes
infinite precision per sample, not just 1 bit/sample.  In practice,
digital video hardware samples at 8 or sometimes 10 bits/sample at
a somewhat higher sample rate  That's 30 Gbytes/hour.  And it's not
exactly easy to convert between sampled NTSC waveforms and RGB images.

>Uncompressed digital 
>is 100 GB, but I mention 95% compression schemes are not difficult (SIGGRAPH
>talk, Sun TAAC board), reducing the need to about 5 GB / hour.

Depends on whether you will accept some degradation in the image,
or insist on lossless compression.