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h264: Complexify frame num gap shortening code

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By observation it did not seem to handle prev_frame_num > frame_num.
This does not affect any files I have.
(cherry picked from commit 43c0092a80f8212cbb783260bafa157f7b85126e)
This commit is contained in:
Alexander Strange 2011-06-02 01:39:56 -07:00 committed by Michael Niedermayer
parent 53781bf13e
commit 33eac92a3c
1 changed files with 14 additions and 3 deletions
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17
libavcodec/h264.c
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@ -2133,9 +2133,20 @@ static int decode_slice_header(H264Context *h, H264Context *h0){
h->mb_field_decoding_flag= s->picture_structure != PICT_FRAME;
if(h0->current_slice == 0){
if(h->frame_num != h->prev_frame_num &&
(h->prev_frame_num+1)%(1<<h->sps.log2_max_frame_num) < (h->frame_num - h->sps.ref_frame_count))
h->prev_frame_num = h->frame_num - h->sps.ref_frame_count - 1;
// Shorten frame num gaps so we don't have to allocate reference frames just to throw them away
if(h->frame_num != h->prev_frame_num) {
int unwrap_prev_frame_num = h->prev_frame_num, max_frame_num = 1<<h->sps.log2_max_frame_num;
if (unwrap_prev_frame_num > h->frame_num) unwrap_prev_frame_num -= max_frame_num;
if ((h->frame_num - unwrap_prev_frame_num) > h->sps.ref_frame_count) {
unwrap_prev_frame_num = (h->frame_num - h->sps.ref_frame_count) - 1;
if (unwrap_prev_frame_num < 0)
unwrap_prev_frame_num += max_frame_num;
h->prev_frame_num = unwrap_prev_frame_num;
}
}
while(h->frame_num != h->prev_frame_num &&
h->frame_num != (h->prev_frame_num+1)%(1<<h->sps.log2_max_frame_num)){