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codecparsers: h264: record number of emulation prevention bytes in slice_header().

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Some hardware video decode acceleration API (VA-API, DXVA) require
a bit count to the first macroblock, minus the number of emulation
prevention bytes. So, instead of having the consumer of the library
scan the slice_header() again, just record that number while parsing.

Signed-off-by: Gwenole Beauchesne <gwenole.beauchesne@intel.com>

https://bugzilla.gnome.org/show_bug.cgi?id=671203
This commit is contained in:
Gwenole Beauchesne 2012-03-02 11:45:41 +01:00 committed by Tim-Philipp Müller
parent 0bb5a01639
commit 5c9f790075
2 changed files with 13 additions and 0 deletions
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10
gst-libs/gst/codecparsers/gsth264parser.c
View file

@ -167,6 +167,7 @@ typedef struct
const guint8 *data;
guint size;
guint n_epb; /* Number of emulation prevention bytes */
guint byte; /* Byte position */
guint bits_in_cache; /* bitpos in the cache of next bit */
guint8 first_byte;
@ -178,6 +179,7 @@ nal_reader_init (NalReader * nr, const guint8 * data, guint size)
{
nr->data = data;
nr->size = size;
nr->n_epb = 0;
nr->byte = 0;
nr->bits_in_cache = 0;
@ -211,6 +213,7 @@ nal_reader_read (NalReader * nr, guint nbits)
((nr->cache & 0xff) == 0)) {
/* next byte goes unconditionally to the cache, even if it's 0x03 */
check_three_byte = FALSE;
nr->n_epb++;
goto next_byte;
}
nr->cache = (nr->cache << 8) | nr->first_byte;
@ -263,6 +266,12 @@ nal_reader_get_remaining (const NalReader * nr)
return (nr->size - nr->byte) * 8 + nr->bits_in_cache;
}
static inline guint
nal_reader_get_epb_count (const NalReader * nr)
{
return nr->n_epb;
}
#define GST_NAL_READER_READ_BITS(bits) \
static gboolean \
nal_reader_get_bits_uint##bits (NalReader *nr, guint##bits *val, guint nbits) \
@ -1882,6 +1891,7 @@ gst_h264_parser_parse_slice_hdr (GstH264NalParser * nalparser,
}
slice->header_size = nal_reader_get_pos (&nr);
slice->n_emulation_prevention_bytes = nal_reader_get_epb_count (&nr);
return GST_H264_PARSER_OK;

3
gst-libs/gst/codecparsers/gsth264parser.h
View file

@ -599,6 +599,9 @@ struct _GstH264SliceHdr
/* Size of the slice_header() in bits */
guint header_size;
/* Number of emulation prevention bytes (EPB) in this slice_header() */
guint n_emulation_prevention_bytes;
};