Jan 13, 2021, 18:46 by tfo...@gmail.com:
> By default the time code scale in a MKV file in millisecond. With this
> option we can set the time code scale to microsecond or nanoseconds for
> very high frame rate.
> ---
> libavformat/matroskaenc.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
> index 233c472b8f..cfad6a4693 100644
> --- a/libavformat/matroskaenc.c
> +++ b/libavformat/matroskaenc.c
> @@ -158,6 +158,8 @@ typedef struct MatroskaMuxContext {
> int default_mode;
>
> uint32_t segment_uid[4];
> +
> + int64_t timecodescale;
> } MatroskaMuxContext;
>
> /** 2 bytes * 7 for EBML IDs, 7 1-byte EBML lengths, 6 1-byte uint,
> @@ -1827,7 +1829,7 @@ static int mkv_write_header(AVFormatContext *s)
> return ret;
> pb = mkv->info.bc;
>
> - put_ebml_uint(pb, MATROSKA_ID_TIMECODESCALE, 1000000);
> + put_ebml_uint(pb, MATROSKA_ID_TIMECODESCALE, mkv->timecodescale);
> if ((tag = av_dict_get(s->metadata, "title", NULL, 0)))
> put_ebml_string(pb, MATROSKA_ID_TITLE, tag->value);
> if (!(s->flags & AVFMT_FLAG_BITEXACT)) {
> @@ -1927,12 +1929,12 @@ static int mkv_write_header(AVFormatContext *s)
> // after 4k and on a keyframe
> if (IS_SEEKABLE(pb, mkv)) {
> if (mkv->cluster_time_limit < 0)
> - mkv->cluster_time_limit = 5000;
> + mkv->cluster_time_limit = 5*(1000000000/mkv->timecodescale);
> if (mkv->cluster_size_limit < 0)
> mkv->cluster_size_limit = 5 * 1024 * 1024;
> } else {
> if (mkv->cluster_time_limit < 0)
> - mkv->cluster_time_limit = 1000;
> + mkv->cluster_time_limit = 1*(1000000000/mkv->timecodescale);
> if (mkv->cluster_size_limit < 0)
> mkv->cluster_size_limit = 32 * 1024;
> }
> @@ -2708,7 +2710,7 @@ static int mkv_init(struct AVFormatContext *s)
> }
>
> // ms precision is the de-facto standard timescale for mkv files
> - avpriv_set_pts_info(st, 64, 1, 1000);
> + avpriv_set_pts_info(st, 64, 1, 1000000000/mkv->timecodescale);
>
> if (st->codecpar->codec_type == AVMEDIA_TYPE_ATTACHMENT) {
> if (mkv->mode == MODE_WEBM) {
> @@ -2795,6 +2797,7 @@ static const AVOption options[] = {
> { "infer", "For each track type, mark the first track of disposition default
> as default; if none exists, mark the first track as default.", 0,
> AV_OPT_TYPE_CONST, { .i64 = DEFAULT_MODE_INFER }, 0, 0, FLAGS, "default_mode"
> },
> { "infer_no_subs", "For each track type, mark the first track of disposition
> default as default; for audio and video: if none exists, mark the first track
> as default.", 0, AV_OPT_TYPE_CONST, { .i64 = DEFAULT_MODE_INFER_NO_SUBS }, 0,
> 0, FLAGS, "default_mode" },
> { "passthrough", "Use the disposition flag as-is", 0, AV_OPT_TYPE_CONST, {
> .i64 = DEFAULT_MODE_PASSTHROUGH }, 0, 0, FLAGS, "default_mode" },
> + { "timecodescale", "Time code scale for all tracks in nanoseconds",
> OFFSET(timecodescale), AV_OPT_TYPE_INT64, { .i64 = 1000000 }, 1, 1000000000,
> FLAGS },
> { NULL },
> };
>
This, x10000000000000000!
Can we make it 1ns by default? Or maybe autodetect the highest precision
timebase of all streams and use it?
Let's not keep generating garbage files with shitty rounding that players
have to work around to recover the original timestamp based on framerate
to reduce jitter (mpv does this!).
Also WebM mode should disable this, because the spec is dumb and specifies
a 1ms precision for no good reason.
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