Start code emulation prevention is only required in Annex B bytestream
packed NAL units. For other coding formats the size is already known.
Looking for a start code prefix can result in false positives like in
http://streams.videolan.org/streams/mp4/Mr_MrsSmith-h264_aac.mp4
which has a false positive in the SPS.
---
libavcodec/h264.c | 11 +++++++++--
libavcodec/h264.h | 5 ++++-
libavcodec/h264_parser.c | 2 +-
3 files changed, 14 insertions(+), 4 deletions(-)
diff --git a/libavcodec/h264.c b/libavcodec/h264.c
index 77acd71..5d4ce90 100644
--- a/libavcodec/h264.c
+++ b/libavcodec/h264.c
@@ -137,7 +137,10 @@ int ff_h264_check_intra_pred_mode(H264Context *h, int
mode){
return mode;
}
-const uint8_t *ff_h264_decode_nal(H264Context *h, const uint8_t *src, int
*dst_length, int *consumed, int length){
+const uint8_t *ff_h264_decode_nal(H264Context *h, const uint8_t *src,
+ int *dst_length, int *consumed, int length,
+ int nalsize_known)
+{
int i, si, di;
uint8_t *dst;
int bufidx;
@@ -148,6 +151,9 @@ const uint8_t *ff_h264_decode_nal(H264Context *h, const
uint8_t *src, int *dst_l
src++; length--;
+ if (nalsize_known) {
+ i = length;
+ } else
#if HAVE_FAST_UNALIGNED
# if HAVE_FAST_64BIT
# define RS 7
@@ -3789,7 +3795,8 @@ static int decode_nal_units(H264Context *h, const uint8_t
*buf, int buf_size){
hx = h->thread_context[context_count];
- ptr= ff_h264_decode_nal(hx, buf + buf_index, &dst_length, &consumed,
next_avc - buf_index);
+ ptr= ff_h264_decode_nal(hx, buf + buf_index, &dst_length, &consumed,
+ next_avc - buf_index, !!nalsize);
if (ptr==NULL || dst_length < 0){
return -1;
}
diff --git a/libavcodec/h264.h b/libavcodec/h264.h
index 5025538..24da4f5 100644
--- a/libavcodec/h264.h
+++ b/libavcodec/h264.h
@@ -610,9 +610,12 @@ int ff_h264_decode_picture_parameter_set(H264Context *h,
int bit_length);
* @param consumed is the number of bytes used as input
* @param length is the length of the array
* @param dst_length is the number of decoded bytes FIXME here or a decode
rbsp tailing?
+ * @param nalsize_known skip start code search if the size of the nalu is known
* @return decoded bytes, might be src+1 if no escapes
*/
-const uint8_t *ff_h264_decode_nal(H264Context *h, const uint8_t *src, int
*dst_length, int *consumed, int length);
+const uint8_t *ff_h264_decode_nal(H264Context *h, const uint8_t *src,
+ int *dst_length, int *consumed, int length,
+ int nalsize_known);
/**
* Free any data that may have been allocated in the H264 context like SPS,
PPS etc.
diff --git a/libavcodec/h264_parser.c b/libavcodec/h264_parser.c
index 826c17a..1967efa 100644
--- a/libavcodec/h264_parser.c
+++ b/libavcodec/h264_parser.c
@@ -144,7 +144,7 @@ static inline int parse_nal_units(AVCodecParserContext *s,
src_length = 20;
break;
}
- ptr= ff_h264_decode_nal(h, buf, &dst_length, &consumed, src_length);
+ ptr= ff_h264_decode_nal(h, buf, &dst_length, &consumed, src_length, 0);
if (ptr==NULL || dst_length < 0)
break;
--
1.7.8
_______________________________________________
libav-devel mailing list
libav-devel@libav.org
https://lists.libav.org/mailman/listinfo/libav-devel
