On 2021-05-19 03:44, michael.di...@xaymar.com wrote:
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 },
  };

I have apparently updated a generated documentation file instead of the source file, and 
did not notice it. The intended documentation for the option 
"timebase_precision" was:

timestamp_precision
Sets the timestamp precision up to 1 nanosecond for Matroska/WebM, which
can improve detection of constant rate content in demuxers. Please note
that increasing the precision reduces the maximum possible timestamp that
can be encoded. Default is 1/1000 (1 millisecond).

Should I resubmit this with the correct documentation patch?

--
Sincerely | Mit freundlichen Grüßen

Michael Fabian 'Xaymar' Dirks
Software Designer & Engineer

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