[FFmpeg-devel] [PATCH] avformat/matroskaenc: Accept time base hint

[Michael Bradshaw]

From: Michael Bradshaw <mjbshaw at google.com>

Signed-off-by: Michael Bradshaw <mjbshaw at google.com>
---
 libavformat/matroskaenc.c | 38 +++++++++++++++++++++++++++++++-------
 1 file changed, 31 insertions(+), 7 deletions(-)

diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 827d755..2c2c930 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -117,6 +117,7 @@ typedef struct mkv_attachments {
 typedef struct MatroskaMuxContext {
     const AVClass  *class;
     int             mode;
+    int             timecode_scale;
     AVIOContext   *dyn_bc;
     AVIOContext     *tags_bc;
     ebml_master     tags;
@@ -1757,7 +1758,7 @@ 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->timecode_scale);
     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)) {
@@ -1799,11 +1800,11 @@ 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(s->duration, 1000000000, AV_TIME_BASE * (int64_t)mkv->timecode_scale);
             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(metadata_duration, 1000000000, AV_TIME_BASE * (int64_t)mkv->timecode_scale);
             put_ebml_float(pb, MATROSKA_ID_DURATION, scaledDuration);
             av_log(s, AV_LOG_DEBUG, "Write early duration from metadata = %" PRIu64 "\n", scaledDuration);
         } else {
@@ -1864,12 +1865,12 @@ static int mkv_write_header(AVFormatContext *s)
     // after 4k and on a keyframe
     if (pb->seekable) {
         if (mkv->cluster_time_limit < 0)
-            mkv->cluster_time_limit = 5000;
+            mkv->cluster_time_limit = av_rescale(5, 1000000000, mkv->timecode_scale);
         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 = 1000000000 / mkv->timecode_scale;
         if (mkv->cluster_size_limit < 0)
             mkv->cluster_size_limit = 32 * 1024;
     }
@@ -2458,6 +2459,7 @@ static int mkv_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->avoid_negative_ts < 0) {
@@ -2465,9 +2467,31 @@ static int mkv_init(struct AVFormatContext *s)
         s->internal->avoid_negative_ts_use_pts = 1;
     }
 
+    // ms precision is the de-facto standard timescale for mkv files
+    mkv->timecode_scale = 1000000;
+
+    // If the user has supplied a desired time base, use it if possible
+    if (s->nb_streams > 0) {
+      AVRational time_base = s->streams[0]->time_base;
+      for (i = 1; i < s->nb_streams; i++) {
+          if (time_base.num != s->streams[i]->time_base.num ||
+              time_base.den != s->streams[i]->time_base.den) {
+            time_base = av_make_q(0, 0);
+            break;
+          }
+      }
+      // Make sure the time base is valid, can losslessly be converted to
+      // nanoseconds, and isn't longer than 1 second
+      if (time_base.num > 0 &&
+          time_base.den > 0 &&
+          1000000000 % time_base.den == 0 &&
+          time_base.num <= time_base.den) {
+          mkv->timecode_scale = (int)av_rescale(time_base.num, 1000000000, time_base.den);
+      }
+    }
+
     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);
+        avpriv_set_pts_info(s->streams[i], 64, mkv->timecode_scale, 1000000000);
     }
 
     return 0;
-- 
2.10.1 (Apple Git-78)