Currently, the Matroska muxer reallocates its array of index entries
each time another entry is added. This is bad performance-wise,
especially on Windows where reallocations are slow. This is solved
by switching to av_fast_realloc_array() which ensures that actual
reallocations will happen only seldomly.
For an (admittedly extreme) example which consists of looping a video
consisting of a single keyframe of size 4KB 540000 times this improved
the time for writing a frame from 23524201 decicycles (516466 runs,
7822 skips) to 225240 decicycles (522122 runs, 2166 skips) on Windows.
(Writing CRC-32 elements was disabled for these tests.)
Signed-off-by: Andreas Rheinhardt <andreas.rheinha...@outlook.com>
---
libavformat/matroskaenc.c | 23 ++++++++++++++++-------
1 file changed, 16 insertions(+), 7 deletions(-)
diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 1256bdfe36..7c7de612de 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -168,7 +168,8 @@ typedef struct mkv_cuepoint {
typedef struct mkv_cues {
mkv_cuepoint *entries;
- int num_entries;
+ size_t num_entries;
+ size_t allocated_entries;
} mkv_cues;
struct MatroskaMuxContext;
@@ -257,6 +258,10 @@ typedef struct MatroskaMuxContext {
/** 4 * (1-byte EBML ID, 1-byte EBML size, 8-byte uint max) */
#define MAX_CUETRACKPOS_SIZE 40
+/** Minimal size of CueTrack, CueClusterPosition and CueRelativePosition,
+ * and 1 + 1 bytes for the overhead of CueTrackPositions itself. */
+#define MIN_CUETRACKPOS_SIZE (1 + 1 + 3 * (1 + 1 + 1))
+
/** 2 + 1 Simpletag header, 2 + 1 + 8 Name "DURATION", 23B for TagString */
#define DURATION_SIMPLETAG_SIZE (2 + 1 + (2 + 1 + 8) + 23)
@@ -914,16 +919,20 @@ static int mkv_add_cuepoint(MatroskaMuxContext *mkv, int
stream, int64_t ts,
int64_t cluster_pos, int64_t relative_pos, int64_t
duration)
{
mkv_cues *cues = &mkv->cues;
- mkv_cuepoint *entries = cues->entries;
- unsigned idx = cues->num_entries;
+ mkv_cuepoint *entries;
+ size_t idx = cues->num_entries;
+ int ret;
if (ts < 0)
return 0;
- entries = av_realloc_array(entries, cues->num_entries + 1,
sizeof(mkv_cuepoint));
- if (!entries)
- return AVERROR(ENOMEM);
- cues->entries = entries;
+ ret = av_fast_realloc_array(&cues->entries, &cues->allocated_entries,
+ cues->num_entries + 1,
+ MAX_SUPPORTED_EBML_LENGTH /
MIN_CUETRACKPOS_SIZE,
+ sizeof(*cues->entries));
+ if (ret < 0)
+ return ret;
+ entries = cues->entries;
/* Make sure the cues entries are sorted by pts. */
while (idx > 0 && entries[idx - 1].pts > ts)
--
2.34.1
_______________________________________________
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
To unsubscribe, visit link above, or email
ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
