@@ -160,6 +160,8 @@ typedef struct MatroskaMuxContext {
int wrote_chapters;
int allow_raw_vfw;
+
+ uint32_t segment_uid[4];
} MatroskaMuxContext;
/** 2 bytes * 7 for EBML IDs, 7 1-byte EBML lengths, 6 1-byte uint,
@@ -1909,15 +1911,7 @@ static int mkv_write_header(AVFormatContext *s)
put_ebml_string(pb, MATROSKA_ID_WRITINGAPP, LIBAVFORMAT_IDENT);
if (mkv->mode != MODE_WEBM) {
- uint32_t segment_uid[4];
- AVLFG lfg;
-
- av_lfg_init(&lfg, av_get_random_seed());
-
- for (i = 0; i < 4; i++)
- segment_uid[i] = av_lfg_get(&lfg);
-
- put_ebml_binary(pb, MATROSKA_ID_SEGMENTUID, segment_uid, 16);
+ put_ebml_binary(pb, MATROSKA_ID_SEGMENTUID, mkv->segment_uid, 16);
}
} else {
const char *ident = "Lavf";
@@ -2738,9 +2732,14 @@ static int mkv_init(struct AVFormatContext *s)
return AVERROR(ENOMEM);
}
- if (!(s->flags & AVFMT_FLAG_BITEXACT))
+ if (!(s->flags & AVFMT_FLAG_BITEXACT)) {
av_lfg_init(&c, av_get_random_seed());
+ // Calculate the SegmentUID now in order not to waste our random seed.
+ for (i = 0; i < 4; i++)
+ mkv->segment_uid[i] = av_lfg_get(&c);
+ }
+
for (i = 0; i < s->nb_streams; i++) {
mkv_track *track = &mkv->tracks[i];
This commit reuses the random seed generated in mkv_init() to determine the TrackUIDs for the SegmentUID in order to avoid a potentially expensive call to av_get_random_seed(). Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com> --- libavformat/matroskaenc.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-)