May 19, 2021, 17:12 by d...@lynne.ee:
> May 19, 2021, 03:44 by michael.di...@xaymar.com:
>
>> From: Michael Fabian 'Xaymar' Dirks <michael.di...@xaymar.com>
>>
>> Adds the "timestamp_precision" option to matroskaenc, which allows users
>> to increase the time stamp precision up to 1 nanosecond. This aids with
>> certain demuxers being unable to detect constant rate. It is a work
>> around fix for the problems reported in 259, 6406, 7927, 8909 and 9124.
>>
>> Signed-off-by: Michael Fabian 'Xaymar' Dirks <michael.di...@xaymar.com>
>> ---
>> libavformat/matroskaenc.c | 25 ++++++++++++++++++-------
>> 1 file changed, 18 insertions(+), 7 deletions(-)
>>
>> diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
>> index b4284a8778..8e2813c36e 100644
>> --- a/libavformat/matroskaenc.c
>> +++ b/libavformat/matroskaenc.c
>> @@ -158,6 +158,8 @@ typedef struct MatroskaMuxContext {
>> int default_mode;
>>
>> uint32_t segment_uid[4];
>> +
>> + AVRational time_base;
>> } MatroskaMuxContext;
>>
>> /** 2 bytes * 7 for EBML IDs, 7 1-byte EBML lengths, 6 1-byte uint,
>> @@ -1816,6 +1818,7 @@ static int mkv_write_header(AVFormatContext *s)
>> const AVDictionaryEntry *tag;
>> int ret, i, version = 2;
>> int64_t creation_time;
>> + int64_t time_base = 1;
>>
>> if (mkv->mode != MODE_WEBM ||
>> av_dict_get(s->metadata, "stereo_mode", NULL, 0) ||
>> @@ -1852,7 +1855,10 @@ static int mkv_write_header(AVFormatContext *s)
>> return ret;
>> pb = mkv->info.bc;
>>
>> - put_ebml_uint(pb, MATROSKA_ID_TIMECODESCALE, 1000000);
>> + time_base = av_rescale_q(time_base, mkv->time_base, (AVRational){1,
>> 1000000000});
>> + av_log(s, AV_LOG_DEBUG, "TimestampScale is: %" PRId64 " ns\n",
>> time_base);
>> + put_ebml_uint(pb, MATROSKA_ID_TIMECODESCALE, time_base);
>> +
>> 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)) {
>> @@ -1885,11 +1891,11 @@ static int mkv_write_header(AVFormatContext *s)
>> int64_t metadata_duration = get_metadata_duration(s);
>>
>> if (s->duration > 0) {
>> - int64_t scaledDuration = av_rescale(s->duration, 1000,
>> AV_TIME_BASE);
>> + int64_t scaledDuration = av_rescale_q(s->duration,
>> AV_TIME_BASE_Q, mkv->time_base);
>> put_ebml_float(pb, MATROSKA_ID_DURATION, scaledDuration);
>> av_log(s, AV_LOG_DEBUG, "Write early duration from recording time = %"
>> PRIu64 "\n", scaledDuration);
>> } else if (metadata_duration > 0) {
>> - int64_t scaledDuration = av_rescale(metadata_duration, 1000,
>> AV_TIME_BASE);
>> + int64_t scaledDuration = av_rescale_q(metadata_duration,
>> AV_TIME_BASE_Q, mkv->time_base);
>> put_ebml_float(pb, MATROSKA_ID_DURATION, scaledDuration);
>> av_log(s, AV_LOG_DEBUG, "Write early duration from metadata = %" PRIu64
>> "\n", scaledDuration);
>> } else if (s->pb->seekable & AVIO_SEEKABLE_NORMAL) {
>> @@ -1950,12 +1956,12 @@ 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 = av_rescale_q(5000, (AVRational){1,
>> 1000}, mkv->time_base);
>> 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 = av_rescale_q(1000, (AVRational){1,
>> 1000}, mkv->time_base);
>> if (mkv->cluster_size_limit < 0)
>> mkv->cluster_size_limit = 32 * 1024;
>> }
>> @@ -2736,8 +2742,8 @@ static int mkv_init(struct AVFormatContext *s)
>> track->uid = mkv_get_uid(mkv->tracks, i, &c);
>> }
>>
>> - // ms precision is the de-facto standard timescale for mkv files
>> - avpriv_set_pts_info(st, 64, 1, 1000);
>> + // Use user-defined timescale.
>> + avpriv_set_pts_info(st, 64, mkv->time_base.num, mkv->time_base.den);
>>
>> if (st->codecpar->codec_type == AVMEDIA_TYPE_ATTACHMENT) {
>> if (mkv->mode == MODE_WEBM) {
>> @@ -2757,6 +2763,10 @@ static int mkv_init(struct AVFormatContext *s)
>> track->track_num_size = ebml_num_size(track->track_num);
>> }
>>
>> + // Scale the configured cluster_time_limit.
>> + if (mkv->cluster_time_limit >= 0)
>> + mkv->cluster_time_limit = av_rescale_q(mkv->cluster_time_limit,
>> (AVRational){1, 1000}, mkv->time_base);
>> +
>> if (mkv->is_dash && nb_tracks != 1)
>> return AVERROR(EINVAL);
>>
>> @@ -2824,6 +2834,7 @@ 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" },
>> + { "timestamp_precision", "Timestamp precision to use for the entire
>> container", OFFSET(time_base), AV_OPT_TYPE_RATIONAL, { .dbl = 0.001 },
>> 0.000000001, 1.0, FLAGS},
>> { NULL },
>> };
>>
>
> Make the default 1 ns.
> This is 2021. I'm not accepting any compromises. Matroska has
> dragged its heels for long enough, video players have resorted to hacks
> to fix time stamps, and high-framerate video is still unacceptably jittery.
>
> We're bumping to 5.0 next release anyway, and if any users have issues,
> they can manually set this to 1ms.
>
Or better yet, use the timebase to decide the value.
That way, remuxing Matroska won't break anything, and the overhead
will be lower.
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