[MPlayer-dev-eng] A question about MPEG-2 XvMC

[Ivan Kalvachev]

On 6/2/09, Cooper Yuan <cooperyuan at gmail.com> wrote:
> Hi,
>
> I have a question about MPEG-2 XvMC acceleration.
> Current mainstream graphics cards are following microsoft DXVA
> specification, that means, the IDCT coefficient data should be zig-zag order
> before being sent to hardware.
> If I use -vo xvmc, does mplayer will pack IDCT coefficient data to zig-zag
> order and then send them to driver?
>
> After review mplayer code, especially vo_xvmc.c, I can't find the function
> which convert raster scan order to zig-zag order. it seems Mplayer send
> raster scan order IDCT data to driver.
>
> so anyone can do me a favor to tell me it's who converts the IDCT
> coefficient data's order?

Not sure what you mean by zig-zag order.
The code that does the coefficient decoding is in ffmpeg/libavcodec
afair coefficients are placed in their respective position
needed for simple matrix IDCT.
(aka de-zigzag is done while reading the coefficients from the bitstream).
Keeping them in the bitstream order, means that you'd have to pass the type
of zig-zag to the IDCT routine.

I hardly think that DXVA is relevant to the hardware implementations
of the card.
Are you trying to do XvMC emulation on windows using DXVA?