[FFmpeg-devel] [PATCH] avoid mb_xy recalculation in h264

[Alexander Strange]

This line appears in a lot of h264.c functions:
const int mb_xy= s->mb_x + s->mb_y*s->mb_stride;

It only changes once per MB, so we can add it to the context and only  
recalculate it in decode_slice().
I put it at the end of H264Context, but it could be moved up earlier  
if someone likes it there. The position doesn't seem to affect  
performance much; it can't be moved next to mb_x/mb_y since that would  
put it in MpegEncContext, and none of the other codecs use it.

Patches:
1- does that, updating it for MBAFF when needed
2- removes some newly unused variables
3- does the same thing to svq3.c

Before: avg 8.799s max 8.8s min 8.794s
After: avg 8.645s max 8.651s min 8.641s

Tested on progressive, PAFF, MBAFF, and svq3. I couldn't find a  
labeled MBAFF file in samples, so I'll put one in incoming.

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