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In <l6ulkqINNjbu@calvin.usc.edu> alves@calvin.usc.edu (William Alves) writes:

>Does anyone with experience in MPEG have a feeling for how long it takes
>to encode full-motion, full-screen video, with enough compression to
>play off a CD-ROM (c. 150k/sec)? I have heard that it would take even
>a high-end personal computer a tremendous amount of time, but I have
>no firm numbers. Also, does anyone know of a company working on a
>QuickTime-compatible MPEG card for the Mac? Thanks.

>Bill Alves


Hi ,
I'm using the Xing Technology MPEG encoder, which works from 320x240
TGA frames .
It takes 1.5 second per frame to encode to a MPEG-file on a 
486 PC (33Mhz) !
I think this is quite fast and all is done by software only !

Best regards Stefan Hartmann.
email to: leo@zelator.in-berlin.de


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*  Stefan Hartmann       This is how to contact me:         *
*  EMAIL: leo@zelator.in-berlin.de                          *
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In article <8LE5E6I@zelator.in-berlin.de> leo@zelator.in-berlin.de (Stefan Hartmann) writes:
>In <l6ulkqINNjbu@calvin.usc.edu> alves@calvin.usc.edu (William Alves) writes:

>>Does anyone with experience in MPEG have a feeling for how long it takes
>>to encode full-motion, full-screen video, with enough compression to
>>play off a CD-ROM (c. 150k/sec)?...

>I'm using the Xing Technology MPEG encoder, which works from 320x240
>TGA frames .
>It takes 1.5 second per frame to encode to a MPEG-file on a 
>486 PC (33Mhz) !
>I think this is quite fast and all is done by software only !

Thanks for the reply, but could you answer a couple other things? I'm
not familiar with the Xing Technology encoder, so can you tell me
what kind of compression ratios you're getting? Are there options
to trade off encoding time for higher compression? If so, do you
have a feeling about what the upper end for this compression and
time scale is? Thanks again.

Bill Alves

In article <8LE5E6I@zelator.in-berlin.de>, leo@zelator.in-berlin.de (Stefan Hartmann) writes:
|> In <l6ulkqINNjbu@calvin.usc.edu> alves@calvin.usc.edu (William Alves) writes:
|> 
|> >Does anyone with experience in MPEG have a feeling for how long it takes
|> >to encode full-motion, full-screen video, with enough compression to
|> >play off a CD-ROM (c. 150k/sec)? I have heard that it would take even
|>      [...]
|> 
|> Hi ,
|> I'm using the Xing Technology MPEG encoder, which works from 320x240
|> TGA frames .
|> It takes 1.5 second per frame to encode to a MPEG-file on a 
|> 486 PC (33Mhz) !
|> I think this is quite fast and all is done by software only !
|> 
|> Best regards Stefan Hartmann.
|> email to: leo@zelator.in-berlin.de
|> 
|> 

This just seems too incredible to me. I can not possibly see how anybody 
can DCT transform a 320x240 frame at that speed on a 486. 

Furthermore I can't see how you could do the motion compensation for an entire frame 
at that speed. The Motion compensation requires an extensive search around each 8x8
pixel block in the image, which amounts to millions of searches just for a single frame.

Another problem which has me confused is that MPEG is not defined for Colourmap
based images which the Xing encoder must use. (you can't do decent real-time colour
quantisation at run time, the images must be pre-quantised, However DCTs do not work
very well with colourmapped images)

I find it hard to believe that the Xing encoder is really MPEG as per the standard.

Ruben.