1. ffmpeg
  2. Commit fdba370f8a1bdfc22ecbdf3c7148c2f8680a4ac4
Browse code

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>

Mans Rullgard authored on 2011/10/12 00:00:21
Showing 2 changed files
libavcodec/golomb.h
History View file @ fdba370
... ... 
@@ -75,6 +75,20 @@ static inline int get_ue_golomb(GetBitContext *gb){
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     }
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 }
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+/**
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+ * Read an unsigned Exp-Golomb code in the range 0 to UINT32_MAX-1.
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+ */
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+static inline unsigned get_ue_golomb_long(GetBitContext *gb)
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+{
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+    unsigned buf, log;
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+
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+    buf = show_bits_long(gb, 32);
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+    log = 31 - av_log2(buf);
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+    skip_bits_long(gb, log);
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+
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+    return get_bits_long(gb, log + 1) - 1;
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+}
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+
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  /**
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  * read unsigned exp golomb code, constraint to a max of 31.
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  * the return value is undefined if the stored value exceeds 31.
libavcodec/h264_ps.c
History View file @ fdba370
... ... 
@@ -130,8 +130,8 @@ static inline int decode_hrd_parameters(H264Context *h, SPS *sps){
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     get_bits(&s->gb, 4); /* bit_rate_scale */
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     get_bits(&s->gb, 4); /* cpb_size_scale */
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     for(i=0; i<cpb_count; i++){
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-        get_ue_golomb(&s->gb); /* bit_rate_value_minus1 */
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-        get_ue_golomb(&s->gb); /* cpb_size_value_minus1 */
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+        get_ue_golomb_long(&s->gb); /* bit_rate_value_minus1 */
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+        get_ue_golomb_long(&s->gb); /* cpb_size_value_minus1 */
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         get_bits1(&s->gb);     /* cbr_flag */
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     }
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     sps->initial_cpb_removal_delay_length = get_bits(&s->gb, 5) + 1;