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, 4 insertions, 3 deletions

diff --git a/libavcodec/filter_units_bsf.c b/libavcodec/filter_units_bsf.c
index 0500dea..bc2ca28 100644
--- a/libavcodec/filter_units_bsf.c
+++ b/libavcodec/filter_units_bsf.c
@@ -139,7 +139,7 @@ static int filter_units_filter(AVBSFContext *bsf, AVPacket *out)
 
         // Don't return packets with nothing in them.
         av_packet_free(&in);
-        ff_cbs_fragment_uninit(ctx->cbc, frag);
+        ff_cbs_fragment_reset(ctx->cbc, frag);
     }
 
     err = ff_cbs_write_packet(ctx->cbc, out, frag);
@@ -153,7 +153,7 @@ static int filter_units_filter(AVBSFContext *bsf, AVPacket *out)
         goto fail;
 
 fail:
-    ff_cbs_fragment_uninit(ctx->cbc, frag);
+    ff_cbs_fragment_reset(ctx->cbc, frag);
     av_packet_free(&in);
 
     return err;
@@ -210,7 +210,7 @@ static int filter_units_init(AVBSFContext *bsf)
                 av_log(bsf, AV_LOG_ERROR, "Failed to write extradata.\n");
         }
 
-        ff_cbs_fragment_uninit(ctx->cbc, frag);
+        ff_cbs_fragment_reset(ctx->cbc, frag);
     }
 
     return err;
@@ -222,6 +222,7 @@ static void filter_units_close(AVBSFContext *bsf)
 
     av_freep(&ctx->type_list);
 
+    ff_cbs_fragment_free(ctx->cbc, &ctx->fragment);
     ff_cbs_close(&ctx->cbc);
 }