From 0d97943b55946b590216e7e8421fac1900352b5b Mon Sep 17 00:00:00 2001 From: Michael Fabian 'Xaymar' Dirks Date: Sun, 23 May 2021 20:17:00 +0200 Subject: [PATCH] avformat/matroskaenc: Allow changing the time stamp precision via option Adds "timestamp_precision" to the available options for Matroska muxing. The option enables users and developers to change the precision of the time stamps in the Matroska container up to 1 nanosecond, which can aid with the proper detection of constant and variable rate content. Work-around fix for: 259, 6406, 7927, 8909 and 9124. Signed-off-by: Michael Fabian 'Xaymar' Dirks --- doc/muxers.texi | 9 +++++++++ libavformat/matroskaenc.c | 34 +++++++++++++++++++++++++++------- 2 files changed, 36 insertions(+), 7 deletions(-) diff --git a/doc/muxers.texi b/doc/muxers.texi index b109297963..30fcd4df4a 100644 --- a/doc/muxers.texi +++ b/doc/muxers.texi @@ -1287,6 +1287,15 @@ Both eyes laced in one Block, Left-eye view is first @item block_rl Both eyes laced in one Block, Right-eye view is first @end table + +@item timestamp_precision +Sets the timestamp precision up to 1 nanosecond for Matroska/WebM, which can +improve detection of constant rate content in demuxers. Note that some poorly +implemented demuxers may require a timestamp precision of 1 millisecond, so +increasing it past that point may result in playback issues. Higher precision +also reduces the maximum possible timestamp significantly. +Default is @var{1/1000} (1 millisecond). + @end table For example a 3D WebM clip can be created using the following command line: diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c index ad7b0bf2c6..a057c735e8 100644 --- a/libavformat/matroskaenc.c +++ b/libavformat/matroskaenc.c @@ -161,6 +161,8 @@ typedef struct MatroskaMuxContext { int64_t *stream_duration_offsets; int allow_raw_vfw; + + AVRational time_base; } MatroskaMuxContext; /** 2 bytes * 7 for EBML IDs, 7 1-byte EBML lengths, 6 1-byte uint, @@ -1863,6 +1865,7 @@ static int mkv_write_header(AVFormatContext *s) AVDictionaryEntry *tag; int ret, i, version = 2; int64_t creation_time; + int64_t time_base = 1; if (!strcmp(s->oformat->name, "webm")) { mkv->mode = MODE_WEBM; @@ -1870,6 +1873,14 @@ static int mkv_write_header(AVFormatContext *s) } else mkv->mode = MODE_MATROSKAv2; + // WebM requires a timestamp precision of 1ms. + if (mkv->mode == MODE_WEBM) { + if (av_cmp_q(mkv->time_base, (AVRational){1, 1000}) != 0) { + av_log(s, AV_LOG_ERROR, "WebM requires 1ms timestamp precision\n"); + return AVERROR(EINVAL); + } + } + if (mkv->mode != MODE_WEBM || av_dict_get(s->metadata, "stereo_mode", NULL, 0) || av_dict_get(s->metadata, "alpha_mode", NULL, 0)) @@ -1917,7 +1928,10 @@ 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)) { @@ -1959,11 +1973,11 @@ 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 { @@ -2038,12 +2052,12 @@ static int mkv_write_header(AVFormatContext *s) // after 4k and on a keyframe if (pb->seekable & AVIO_SEEKABLE_NORMAL) { 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; } @@ -2723,6 +2737,7 @@ static int webm_query_codec(enum AVCodecID codec_id, int std_compliance) static int mkv_init(struct AVFormatContext *s) { + MatroskaMuxContext *mkv = s->priv_data; int i; if (s->nb_streams > MAX_TRACKS) { @@ -2752,10 +2767,14 @@ static int mkv_init(struct AVFormatContext *s) } for (i = 0; i < s->nb_streams; i++) { - // ms precision is the de-facto standard timescale for mkv files - avpriv_set_pts_info(s->streams[i], 64, 1, 1000); + // Use user-defined timescale. + avpriv_set_pts_info(s->streams[i], 64, mkv->time_base.num, mkv->time_base.den); } + // 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); + return 0; } @@ -2815,6 +2834,7 @@ static const AVOption options[] = { { "live", "Write files assuming it is a live stream.", OFFSET(is_live), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, FLAGS }, { "allow_raw_vfw", "allow RAW VFW mode", OFFSET(allow_raw_vfw), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, FLAGS }, { "write_crc32", "write a CRC32 element inside every Level 1 element", OFFSET(write_crc), AV_OPT_TYPE_BOOL, { .i64 = 1 }, 0, 1, FLAGS }, + { "timestamp_precision", "Timestamp precision to use for the entire container", OFFSET(time_base), AV_OPT_TYPE_RATIONAL, { .dbl = 0.001 }, 0.000000001, INT_MAX, FLAGS}, { NULL }, }; -- 2.31.1.windows.1