From 33eac92a3c1aa0f3d0b5bbc6893ed5f646ee527c Mon Sep 17 00:00:00 2001 From: Alexander Strange Date: Thu, 2 Jun 2011 01:39:56 -0700 Subject: [PATCH] h264: Complexify frame num gap shortening code 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) --- libavcodec/h264.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/libavcodec/h264.c b/libavcodec/h264.c index dfe9d4a6a5..7d54e1c6c1 100644 --- a/libavcodec/h264.c +++ b/libavcodec/h264.c @@ -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<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<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<sps.log2_max_frame_num)){