[FFmpeg-devel] hardware aided video decoding

[Attila Kinali]

On Fri, 6 Jul 2007 09:43:32 -0600 (MDT)
Loren Merritt <lorenm at u.washington.edu> wrote:

> common mc:
> The primitive operation of mc is a fir filter. Implement a 2/4/6/8-tap 
> fir filter (applying to a block of pixels) with programmable coefficients 
> and rounding modes, and allow the firs to be chained in arbitrary ways.
> A generic fir filter could by used for wavelets too.
> mpeg4 qpel also has some weirdness whereby it mirrors the block edges 
> before sending them into the 8-tap.

I don't understand how you can abstract MC to a FIR filter.
>From my understanding of MC (which might be wrong) MC uses
a vector pointing into the previously decoded frame to predict
the currently processed macro block. To me, that's an operation
that rather resambles a texture mapping than a FIR filter.

Can you explain this a little bit further?


> Decoding a h264 intra block in a software codec:
> idct the residual of this block.
> Predict the pixels of this block, using the decoded pixels of the 
> neighboring blocks (all neighbors: left, top-left, top, top-right), using 
> 1 of 22 prediction modes.
> Add residual to prediction.
> Use these newly decoded samples to predict the next block...
> 
> If you want to do the prediction in hardware without the idct, that's 
> possible.

This rather sounds like i would like to leave that completely
in software, as the host cpu has better memory bandwidth and
has less trouble to handle large and random memory accesses.

			Attila Kinali

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