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FFmpeg/patches/4.2/0001-avformat-matroskaenc-Allow-changing-the-time-stamp-p.patch
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Michael Fabian 'Xaymar' Dirks 07af655f36 patches: Fix 45be7d3194 for 4.2
2021-05-23 20:54:20 +02:00

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From 0d97943b55946b590216e7e8421fac1900352b5b Mon Sep 17 00:00:00 2001
From: Michael Fabian 'Xaymar' Dirks <info@xaymar.com>
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 <michael.dirks@xaymar.com>
---
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
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