ff_huff_build_tree uses qsort underneath. AV_QSORT is substantially
faster due to the inlining of the comparison callback. Furthermore, this
code is reasonably performance critical, since in e.g the fraps codec,
ff_huff_build_tree is called on every frame. This routine is also called
in vp6 on every frame in some circumstances.
Sample benchmark (x86-64, Haswell, GNU/Linux), fraps-v2 from FATE:
new:
280110 decicycles in qsort, 1 runs, 0 skips
268260 decicycles in qsort, 2 runs, 0 skips
old:
1469910 decicycles in qsort, 1 runs, 0 skips
952950 decicycles in qsort, 2 runs, 0 skips
Signed-off-by: Ganesh Ajjanagadde <gajjanaga...@gmail.com>
---
libavcodec/huffman.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/libavcodec/huffman.c b/libavcodec/huffman.c
index c771bcf..d7403b8 100644
--- a/libavcodec/huffman.c
+++ b/libavcodec/huffman.c
@@ -26,6 +26,7 @@
#include <stdint.h>
+#include "libavutil/qsort.h"
#include "avcodec.h"
#include "get_bits.h"
#include "huffman.h"
@@ -170,7 +171,7 @@ int ff_huff_build_tree(AVCodecContext *avctx, VLC *vlc, int
nb_codes, int nb_bit
"Tree construction is not possible\n");
return -1;
}
- qsort(nodes, nb_codes, sizeof(Node), cmp);
+ AV_QSORT(nodes, nb_codes, Node, cmp);
cur_node = nb_codes;
nodes[nb_codes*2-1].count = 0;
for (i = 0; i < nb_codes * 2 - 1; i += 2) {
--
2.6.2
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