🚀 go-pugleaf

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
>     [...]

leo@zelator.in-berlin.de (Stefan Hartmann) writes:
> 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 !

ruben@europa.ee.uts.edu.au (Ruben Gonzalez) writes:
>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.

mike@optimla.aimla.com (Mike Diehr) writes:
>I agree.  We have a MPEG encoder, which I believe is sun SPARC based, and it
>runs about 100:1. (i.e. 1 second of video takes 100 seconds to encode).

As I understand it, the Xing encoder currently only does I-Frames... that is
it does no motion compensation and uses empty B and P-Frames.  This way
the compression is faster and you still get 10 frames a second encoded in
a byte stream that is usually only about 50kB/sec (well under CD-ROM).
The quality of the image is more than satisfactory for viewing at 320x240
although it could use some better pre- and post-filtering.
(Disclaimer... I could be wrong about all this, but this is what I've been
led to believe)

I'm not sure how long their full encoder takes (with B and P-Frames), but
Stefan is right about their currently released encoder's speed.  As I 
understand the MPEG spec, their files are compliant with the spec, but
just don't use it to its full extent.

Stephen.

Stephen D'Angelo, IBM Multimedia Lab, Palo Alto CA
stephen@ibmpa.awdpa.ibm.com