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From: julian@axcn01.cern.ch (Julian James Bunn)
Subject: Re: Low cost image processing on PCs
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Date: Wed, 22 Feb 1995 15:06:52 GMT
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In article <792956697snx@iai.mv.com>, tut@iai.mv.com (Bill Tuttle) writes:
>6642@sbsun0010.UUCP writes in article <3htupv$h7e@hacgate2.hac.com>:
>> 
>> Dear netters,
>> 
>> I would like to do some basic image processing on PC with one of the
>> off-the-shelf video capture cards.  The task is to grab 640 x 480,
>> 1 to 8 bit grey scale, ~30 frames/second; capture into RAM, no compression,
>> no disk recording; do the computation and display back to VGA display at
>> the same frame rate.
>> 
>> What is your experience with the following cards concerning:
>> 1. Throughput - because capture and display occurs on the same PC bus, will
>>    ISA, EISA cards be sufficient, or should I go for VLB, PCI cards?
>> 2. Developer/OS support - RAM access in particular, since we will be developing
>>    our own software.
>> 
>> Some of the video capture cards we are considering:
>> 1. QuickVIA from Jovian Logic.
>> 2. ComputerEyes from Digital Vision.			 
>> 3. Video Blaster from Creative Labs.
>> 4. Video-It! from ATI.
>> 
>
>1.  None of these cards capture 640 x 480 natively(see below). They get there
>    for single frame capture with scaling.  In addition to not giving you the
>    resolution you require, the scaling impacts performance.
>
>        1. QuickVIA from Jovian Logic.        320x240
>        2. ComputerEyes from Digital Vision.  512x480
>        3. Video Blaster from Creative Labs.  320x240
>        4. Video-It! from ATI.                320x240
>
>2.  All of these cards are ISA bus cards and can not sustain the data rates
>    you require(640x480 = 300K pixels = 9 MB capture, 9MB display).
>    You would certainly require either VLB or PCI bus performance.
>
>3.  Even if you could solve the data transfer problems, your computation
>    restrictions are even worse.  On a 486 DX2-66 each clock for all 300K
>    pixels takes 4.608ms.
>
>4.  You really have two choices.  Get a frame grabber that has hardware
>    ALU/DSP capability onboard or be prepared for MUCH slower operations.
>
>
>Bill Tuttle -- tut@iai.mv.com
>


Maybe you'd be interested in the rate I'm getting on a super-low-cost
solution: around 4 frames/second in a 200x160 8 bit colour window, using
a MediaVision ProMovie Spectrum card, 386DX40 PC and all the processing
routines written in MASM . (The processing does scan line cut, rotate and
matching for the whole frame.)

Actually I'm quite pleased with this: the Spectrum card goes for a song
and a dance, so I wasn't expecting very much. It's also easy to program.

This has to be the lowest end of the spectrum (excuse pun).

Julian



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Julian James Bunn / CERN Computing and Networks Division. Tel.: Geneva 767 5029
Email: julian@vxcern.cern.ch                             CompuServe: 100327,317
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