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, 5 insertions, 4 deletions

diff --git a/libavcodec/vaapi_encode_h264.c b/libavcodec/vaapi_encode_h264.c
index 4ea62d96f3..9f984ec60d 100644
--- a/libavcodec/vaapi_encode_h264.c
+++ b/libavcodec/vaapi_encode_h264.c
@@ -174,7 +174,7 @@ static int vaapi_encode_h264_write_sequence_header(AVCodecContext *avctx,
 
     err = vaapi_encode_h264_write_access_unit(avctx, data, data_len, au);
 fail:
-    ff_cbs_fragment_uninit(priv->cbc, au);
+    ff_cbs_fragment_reset(priv->cbc, au);
     return err;
 }
 
@@ -200,7 +200,7 @@ static int vaapi_encode_h264_write_slice_header(AVCodecContext *avctx,
 
     err = vaapi_encode_h264_write_access_unit(avctx, data, data_len, au);
 fail:
-    ff_cbs_fragment_uninit(priv->cbc, au);
+    ff_cbs_fragment_reset(priv->cbc, au);
     return err;
 }
 
@@ -264,7 +264,7 @@ static int vaapi_encode_h264_write_extra_header(AVCodecContext *avctx,
         if (err < 0)
             goto fail;
 
-        ff_cbs_fragment_uninit(priv->cbc, au);
+        ff_cbs_fragment_reset(priv->cbc, au);
 
         *type = VAEncPackedHeaderRawData;
         return 0;
@@ -286,7 +286,7 @@ static int vaapi_encode_h264_write_extra_header(AVCodecContext *avctx,
     }
 
 fail:
-    ff_cbs_fragment_uninit(priv->cbc, au);
+    ff_cbs_fragment_reset(priv->cbc, au);
     return err;
 }
 
@@ -1233,6 +1233,7 @@ static av_cold int vaapi_encode_h264_close(AVCodecContext *avctx)
 {
     VAAPIEncodeH264Context *priv = avctx->priv_data;
 
+    ff_cbs_fragment_free(priv->cbc, &priv->current_access_unit);
     ff_cbs_close(&priv->cbc);
     av_freep(&priv->sei_identifier_string);