libavcodec/cbs: Stop needlessly reallocating the units array

Currently, a fragment's unit array is constantly reallocated during
splitting of a packet. This commit changes this: One can keep the units
array by distinguishing between the number of allocated and the number
of valid units in the units array.

The more units a packet is split into, the bigger the benefit.
So MPEG-2 benefits the most; for a video coming from an NTSC-DVD
(usually 32 units per frame) the average cost of cbs_insert_unit (for a
single unit) went down from 6717 decicycles to 450 decicycles (based
upon 10 runs with 4194304 runs each); if each packet consists of only
one unit, it went down from 2425 to 448; for a H.264 video where most
packets contain nine units, it went from 4431 to 450.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@googlemail.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/libavcodec/av1_parser.c b/libavcodec/av1_parser.c
index 8df66498f4..bb8737a393 100644
--- a/libavcodec/av1_parser.c
+++ b/libavcodec/av1_parser.c
@@ -72,7 +72,7 @@ static int av1_parser_parse(AVCodecParserContext *ctx,
             goto end;
         }
 
-        ff_cbs_fragment_uninit(s->cbc, td);
+        ff_cbs_fragment_reset(s->cbc, td);
     }
 
     ret = ff_cbs_read(s->cbc, td, data, size);
@@ -159,7 +159,7 @@ static int av1_parser_parse(AVCodecParserContext *ctx,
     }
 
 end:
-    ff_cbs_fragment_uninit(s->cbc, td);
+    ff_cbs_fragment_reset(s->cbc, td);
 
     s->cbc->log_ctx = NULL;
 
@@ -193,6 +193,7 @@ static void av1_parser_close(AVCodecParserContext *ctx)
 {
     AV1ParseContext *s = ctx->priv_data;
 
+    ff_cbs_fragment_free(s->cbc, &s->temporal_unit);
     ff_cbs_close(&s->cbc);
 }