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h264: fix detection of optional trailing PPS elements

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The PPS may contain a few trailing elements whose presence is
only signalled by data remaining after the the mandatory part
has been parsed.  The current code fails to take into account
the rbsp_trailing_bits() when deciding whether to parse these
optional elements.  Assuming no unnecessary padding bytes are
passed to this function, the optional elements are present if
either more than 8 extra bits remain or the remaining bits do
not form a valid rbsp_trailing_bits() after the mandatory PPS
elements have been parsed.

Signed-off-by: Mans Rullgard <mans@mansr.com>
This commit is contained in:
Mans Rullgard 2011-10-11 00:58:03 +01:00
parent c79d2a20ba
commit be1242a3f2
1 changed files with 4 additions and 1 deletions
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5
libavcodec/h264_ps.c
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@ -462,6 +462,7 @@ int ff_h264_decode_picture_parameter_set(H264Context *h, int bit_length){
unsigned int pps_id= get_ue_golomb(&s->gb);
PPS *pps;
const int qp_bd_offset = 6*(h->sps.bit_depth_luma-8);
int bits_left;
if(pps_id >= MAX_PPS_COUNT) {
av_log(h->s.avctx, AV_LOG_ERROR, "pps_id (%d) out of range\n", pps_id);
@ -538,7 +539,9 @@ int ff_h264_decode_picture_parameter_set(H264Context *h, int bit_length){
memcpy(pps->scaling_matrix4, h->sps_buffers[pps->sps_id]->scaling_matrix4, sizeof(pps->scaling_matrix4));
memcpy(pps->scaling_matrix8, h->sps_buffers[pps->sps_id]->scaling_matrix8, sizeof(pps->scaling_matrix8));
if(get_bits_count(&s->gb) < bit_length){
bits_left = bit_length - get_bits_count(&s->gb);
if (bits_left && (bits_left > 8 ||
show_bits(&s->gb, bits_left) != 1 << (bits_left - 1))) {
pps->transform_8x8_mode= get_bits1(&s->gb);
decode_scaling_matrices(h, h->sps_buffers[pps->sps_id], pps, 0, pps->scaling_matrix4, pps->scaling_matrix8);
pps->chroma_qp_index_offset[1]= get_se_golomb(&s->gb); //second_chroma_qp_index_offset