[FFmpeg-devel] libavcodec/blockdsp : add clear_blocks_prores func (SSE, AVX) for prores decoding

[Ronald S. Bultje]

Hi Martin,

(as you've probably noticed, I'm generally particularly interested in
optimization patches, not just the SIMD, but also the general algorithmic
thought behind it.)

On Thu, Oct 5, 2017 at 10:58 AM, Martin Vignali <martin.vignali at gmail.com>
wrote:

> In attach patchs to add a dedicated func for clear_block inside
> prores decoding (proresdec2)
>

The idea here is that N (where N=blocks_per_slice) calls is more expensive
than 1 call, which is indeed true. One way we've tried to "fix" this in
some decoders is to not call clear_blocks() at all, instead clearing the
coefficient arrays in the call to idct() - see e.g. h264/hevc, vp8/9, and
probably some more. Given that the prores idct lives in its own
proresdspcontext, we could adjust it here as well. The advantage of having
0 calls should be obvious. :-).

Ronald