[FFmpeg-devel] [PATCH 8/9] avformat/matroskaenc: Improve cues in case of no-video

[Andreas Rheinhardt]

The Matroska muxer currently only adds CuePoints in three cases:
a) For video keyframes. b) For the first audio frame in a new cluster if
in dash-mode. c) For subtitles. This means that ordinary Matroska audio
files won't have any cues which impedes seeking.

This commit changes this. For every track in a file without video track
it is checked and tracked whether a cue entry has already been added
for said track for the current cluster. This is used to add a cue entry
for each first packet of each track in each cluster.

Implements #3149.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
---
 libavformat/matroskaenc.c            | 21 ++++++++++++---------
 tests/ref/fate/aac-autobsf-adtstoasc |  4 ++--
 tests/ref/lavf/mka                   |  4 ++--
 3 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 7c9941c567..1a3d337e5b 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -2253,6 +2253,10 @@ static void mkv_end_cluster(AVFormatContext *s)
     MatroskaMuxContext *mkv = s->priv_data;
 
     end_ebml_master_crc32(s->pb, &mkv->cluster_bc, mkv);
+    if (!mkv->have_video) {
+        for (int i = 0; i < s->nb_streams; i++)
+            mkv->tracks[i].has_cue = 0;
+    }
     mkv->cluster_pos = -1;
     avio_flush(s->pb);
 }
@@ -2365,7 +2369,7 @@ static int mkv_check_new_extra_data(AVFormatContext *s, AVPacket *pkt)
     return 0;
 }
 
-static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt, int add_cue)
+static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt)
 {
     MatroskaMuxContext *mkv = s->priv_data;
     AVIOContext *pb;
@@ -2410,9 +2414,11 @@ static int mkv_write_packet_internal(AVFormatContext *s, AVPacket *pkt, int add_
 
     if (par->codec_type != AVMEDIA_TYPE_SUBTITLE) {
         mkv_write_block(s, pb, MATROSKA_ID_SIMPLEBLOCK, pkt, keyframe);
-        if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) && (par->codec_type == AVMEDIA_TYPE_VIDEO && keyframe || add_cue)) {
+        if ((s->pb->seekable & AVIO_SEEKABLE_NORMAL) && keyframe &&
+            (par->codec_type == AVMEDIA_TYPE_VIDEO || !mkv->have_video && !track->has_cue)) {
             ret = mkv_add_cuepoint(mkv->cues, pkt->stream_index, tracknum, ts, mkv->cluster_pos, relative_packet_pos, -1);
             if (ret < 0) return ret;
+            track->has_cue = 1;
         }
     } else {
         if (par->codec_id == AV_CODEC_ID_WEBVTT) {
@@ -2479,8 +2485,7 @@ static int mkv_write_packet(AVFormatContext *s, AVPacket *pkt)
         // on seeing key frames.
         start_new_cluster = keyframe;
     } else if (mkv->is_dash && codec_type == AVMEDIA_TYPE_AUDIO &&
-               (mkv->cluster_pos == -1 ||
-                cluster_time > mkv->cluster_time_limit)) {
+               cluster_time > mkv->cluster_time_limit) {
         // For DASH audio, we create a Cluster based on cluster_time_limit
         start_new_cluster = 1;
     } else if (!mkv->is_dash &&
@@ -2504,9 +2509,7 @@ static int mkv_write_packet(AVFormatContext *s, AVPacket *pkt)
 
     // check if we have an audio packet cached
     if (mkv->cur_audio_pkt.size > 0) {
-        // for DASH audio, a CuePoint has to be added when there is a new cluster.
-        ret = mkv_write_packet_internal(s, &mkv->cur_audio_pkt,
-                                        mkv->is_dash ? start_new_cluster : 0);
+        ret = mkv_write_packet_internal(s, &mkv->cur_audio_pkt);
         av_packet_unref(&mkv->cur_audio_pkt);
         if (ret < 0) {
             av_log(s, AV_LOG_ERROR,
@@ -2521,7 +2524,7 @@ static int mkv_write_packet(AVFormatContext *s, AVPacket *pkt)
         if (pkt->size > 0)
             ret = av_packet_ref(&mkv->cur_audio_pkt, pkt);
     } else
-        ret = mkv_write_packet_internal(s, pkt, 0);
+        ret = mkv_write_packet_internal(s, pkt);
     return ret;
 }
 
@@ -2550,7 +2553,7 @@ static int mkv_write_trailer(AVFormatContext *s)
 
     // check if we have an audio packet cached
     if (mkv->cur_audio_pkt.size > 0) {
-        ret = mkv_write_packet_internal(s, &mkv->cur_audio_pkt, 0);
+        ret = mkv_write_packet_internal(s, &mkv->cur_audio_pkt);
         av_packet_unref(&mkv->cur_audio_pkt);
         if (ret < 0) {
             av_log(s, AV_LOG_ERROR,
diff --git a/tests/ref/fate/aac-autobsf-adtstoasc b/tests/ref/fate/aac-autobsf-adtstoasc
index 9bf9dfe78f..a94364c213 100644
--- a/tests/ref/fate/aac-autobsf-adtstoasc
+++ b/tests/ref/fate/aac-autobsf-adtstoasc
@@ -1,5 +1,5 @@
-b09fc2f554712adbf84fe7899eb679d4 *tests/data/fate/aac-autobsf-adtstoasc.matroska
-6695 tests/data/fate/aac-autobsf-adtstoasc.matroska
+f1bccaa7ab4967e7dc4f5b07c372b040 *tests/data/fate/aac-autobsf-adtstoasc.matroska
+6723 tests/data/fate/aac-autobsf-adtstoasc.matroska
 #extradata 0:        2, 0x0030001c
 #tb 0: 1/1000
 #media_type 0: audio
diff --git a/tests/ref/lavf/mka b/tests/ref/lavf/mka
index a244893cf2..f51f465533 100644
--- a/tests/ref/lavf/mka
+++ b/tests/ref/lavf/mka
@@ -1,3 +1,3 @@
-a91bfdb08ff5a1e62b039748d16b07f7 *tests/data/lavf/lavf.mka
-43652 tests/data/lavf/lavf.mka
+cc12a53d175adf8f39dcfa69d27928dc *tests/data/lavf/lavf.mka
+43680 tests/data/lavf/lavf.mka
 tests/data/lavf/lavf.mka CRC=0x3a1da17e
-- 
2.20.1