[Openchrome-users] XvMC status

[Ivor Hewitt]

St?phane Konstantaropoulos wrote:
> Hi All,
> 
> I got a laptop with a VIA C7 and a PN800 in it, I was wondering what was the 
> status of the XvMC for such a chip?
> 
MPEG2 xvmc generally works. The PN800 only does MPEG2 decoding.

http://www.via.com.tw/en/products/chipsets/p4-series/comparison_p4-series.jsp

> What's the status of MPEG4?
> 
On hold.

> I'd be interested into hacking the driver to try and get MPEG4 and H263 to 
> work. Is there any specifications / documentation for the chip internals 
> somewhere?
> 
I posted my initial findings on this earlier with a 1Ghz CN400. 
Basically the MPEG4 accel in these chips only provides MC/DCT level 
decoding and only for H.263 at that. I found that the processing 
required to feed the MC data to the decoder meant that for the streams I 
tested it just wasn't worth using the hardware decoder (perhaps a reason 
why the MPEG4 decoding was dropped from all subsequent unichrome-pro's).
also.... most h263 streams are low bitrate and easy to decode in 
software even on low cpu machines... and most broadcasters are using 
h.264 for mpeg4 instead.

> Is there any XvMC implementation of XVMC_MPEG4 and / or XVMC_H263 around at 
> all? (even for other cards, to get some inspiration).
>
Not that I know of. There's a few decent software mpeg4 
implementations.... the only other appropriate code is the via mplayer 
patch to enable h263 accel with the via binary driver.


Ivor.