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h264: fix HRD parameters parsing 

The bit_rate_value_minus1 and cpb_size_value_minus1 elements
allow a wider range than get_ue_golomb() supports.  This
adds a get_ue_golomb_long() function supporting up to 31
leading zeros, which is the maximum for these syntax
elements, and uses it in decode_hrd_parameters().

Signed-off-by: Mans Rullgard <mans@mansr.com>
This commit is contained in:
Mans Rullgard 2011-10-11 16:00:21 +01:00
parent 91f4732913
commit fdba370f8a
2 changed files with 16 additions and 2 deletions
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14
libavcodec/golomb.h
View File

@ -75,6 +75,20 @@ static inline int get_ue_golomb(GetBitContext *gb){
}
}
/**
* Read an unsigned Exp-Golomb code in the range 0 to UINT32_MAX-1.
*/
static inline unsigned get_ue_golomb_long(GetBitContext *gb)
{
unsigned buf, log;
buf = show_bits_long(gb, 32);
log = 31 - av_log2(buf);
skip_bits_long(gb, log);
return get_bits_long(gb, log + 1) - 1;
}
/**
* read unsigned exp golomb code, constraint to a max of 31.
* the return value is undefined if the stored value exceeds 31.

4
libavcodec/h264_ps.c
View File

@ -130,8 +130,8 @@ static inline int decode_hrd_parameters(H264Context *h, SPS *sps){
get_bits(&s->gb, 4); /* bit_rate_scale */
get_bits(&s->gb, 4); /* cpb_size_scale */
for(i=0; i<cpb_count; i++){
get_ue_golomb(&s->gb); /* bit_rate_value_minus1 */
get_ue_golomb(&s->gb); /* cpb_size_value_minus1 */
get_ue_golomb_long(&s->gb); /* bit_rate_value_minus1 */
get_ue_golomb_long(&s->gb); /* cpb_size_value_minus1 */
get_bits1(&s->gb); /* cbr_flag */
}
sps->initial_cpb_removal_delay_length = get_bits(&s->gb, 5) + 1;