[FFmpeg-devel] [PATCH 05/11] avcodec/h264_parser: Reuse the RBSP buffer

[Andreas Rheinhardt]

Up until now, the H.264 parser has allocated a new buffer for every
frame in order to store the unescaped RBSP in case the part of the RBSP
that will be unescaped contains 0x03 escape bytes. This is expensive
and this commit changes this: The buffer is now kept and reused.

For an AVC file with an average framesize of 15304 B (without in-band
parameter sets etc.) and 132044 frames (131072 of which ended up in the
results) this reduced the average time used by the H.264 parser from
87708 decicycles (excluding about 1100-1200 skips in each iteration)
to 16963 decicycles (excluding about 10-15 skips in each iteration).
The test has been iterated 10 times.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
---
 libavcodec/h264_parser.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/libavcodec/h264_parser.c b/libavcodec/h264_parser.c
index 5f9a9c46ef..c200a2ab8e 100644
--- a/libavcodec/h264_parser.c
+++ b/libavcodec/h264_parser.c
@@ -53,6 +53,7 @@ typedef struct H264ParseContext {
     H264DSPContext h264dsp;
     H264POCContext poc;
     H264SEIContext sei;
+    H2645RBSP rbsp;
     int is_avc;
     int nal_length_size;
     int got_first;
@@ -246,7 +247,7 @@ static inline int parse_nal_units(AVCodecParserContext *s,
                                   const uint8_t * const buf, int buf_size)
 {
     H264ParseContext *p = s->priv_data;
-    H2645RBSP rbsp = { NULL };
+    H2645RBSP *rbsp = &p->rbsp;
     H2645NAL nal = { NULL };
     int buf_index, next_avc;
     unsigned int pps_id;
@@ -267,9 +268,10 @@ static inline int parse_nal_units(AVCodecParserContext *s,
     if (!buf_size)
         return 0;
 
-    av_fast_padded_malloc(&rbsp.rbsp_buffer, &rbsp.rbsp_buffer_alloc_size, buf_size);
-    if (!rbsp.rbsp_buffer)
+    av_fast_padded_malloc(&rbsp->rbsp_buffer, &rbsp->rbsp_buffer_alloc_size, buf_size);
+    if (!rbsp->rbsp_buffer)
         return AVERROR(ENOMEM);
+    rbsp->rbsp_buffer_size = 0;
 
     buf_index     = 0;
     next_avc      = p->is_avc ? 0 : buf_size;
@@ -308,7 +310,7 @@ static inline int parse_nal_units(AVCodecParserContext *s,
             }
             break;
         }
-        consumed = ff_h2645_extract_rbsp(buf + buf_index, src_length, &rbsp, &nal, 1);
+        consumed = ff_h2645_extract_rbsp(buf + buf_index, src_length, rbsp, &nal, 1);
         if (consumed < 0)
             break;
 
@@ -554,18 +556,15 @@ static inline int parse_nal_units(AVCodecParserContext *s,
                 p->last_frame_num = p->poc.frame_num;
             }
 
-            av_freep(&rbsp.rbsp_buffer);
             return 0; /* no need to evaluate the rest */
         }
     }
     if (q264) {
-        av_freep(&rbsp.rbsp_buffer);
         return 0;
     }
     /* didn't find a picture! */
     av_log(avctx, AV_LOG_ERROR, "missing picture in access unit with size %d\n", buf_size);
 fail:
-    av_freep(&rbsp.rbsp_buffer);
     return -1;
 }
 
@@ -690,6 +689,8 @@ static void h264_close(AVCodecParserContext *s)
     ParseContext *pc = &p->pc;
 
     av_freep(&pc->buffer);
+    av_freep(&p->rbsp.rbsp_buffer);
+    p->rbsp.rbsp_buffer_alloc_size = 0;
 
     ff_h264_sei_uninit(&p->sei);
     ff_h264_ps_uninit(&p->ps);
-- 
2.21.0