[FFmpeg-devel] [PATCH 4/4] lavf/matroskaenc: mux WebVTT using standard (non-WebM) formatting

[rcombs]

---
 libavformat/matroskaenc.c | 33 +++++++++++++++++++++++++--------
 1 file changed, 25 insertions(+), 8 deletions(-)

diff --git a/libavformat/matroskaenc.c b/libavformat/matroskaenc.c
index 1f7a9528de..d34a47e646 100644
--- a/libavformat/matroskaenc.c
+++ b/libavformat/matroskaenc.c
@@ -1351,7 +1351,7 @@ static int mkv_write_track(AVFormatContext *s, MatroskaMuxContext *mkv,
             return AVERROR(ENOSYS);
         }
 
-        if (mkv->mode != MODE_WEBM || par->codec_id != AV_CODEC_ID_WEBVTT)
+        if (mkv->mode != MODE_WEBM)
             native_id = MATROSKA_TRACK_TYPE_SUBTITLE;
 
         put_ebml_uint(pb, MATROSKA_ID_TRACKTYPE, native_id);
@@ -1361,7 +1361,7 @@ static int mkv_write_track(AVFormatContext *s, MatroskaMuxContext *mkv,
         return AVERROR(EINVAL);
     }
 
-    if (mkv->mode != MODE_WEBM || par->codec_id != AV_CODEC_ID_WEBVTT) {
+    if (mkv->mode != MODE_WEBM) {
         track->codecpriv_offset = avio_tell(pb);
         ret = mkv_write_codecprivate(s, pb, par, native_id, qt_id);
         if (ret < 0)
@@ -2117,20 +2117,22 @@ static int mkv_write_vtt_blocks(AVFormatContext *s, AVIOContext *pb, const AVPac
     MatroskaMuxContext *mkv = s->priv_data;
     mkv_track *track = &mkv->tracks[pkt->stream_index];
     ebml_master blockgroup;
-    int id_size, settings_size, size;
-    uint8_t *id, *settings;
+    int id_size = 0, settings_size = 0, comment_size = 0, size = pkt->size;
+    uint8_t *id, *settings, *comment;
     int64_t ts = track->write_dts ? pkt->dts : pkt->pts;
     const int flags = 0;
 
-    id_size = 0;
     id = av_packet_get_side_data(pkt, AV_PKT_DATA_WEBVTT_IDENTIFIER,
                                  &id_size);
 
-    settings_size = 0;
     settings = av_packet_get_side_data(pkt, AV_PKT_DATA_WEBVTT_SETTINGS,
                                        &settings_size);
 
-    size = id_size + 1 + settings_size + 1 + pkt->size;
+    comment = av_packet_get_side_data(pkt, AV_PKT_DATA_WEBVTT_COMMENT,
+                                      &comment_size);
+
+    if (mkv->mode == MODE_WEBM)
+        size += id_size + 1 + settings_size + 1;
 
     /* The following string is identical to the one in mkv_write_block so that
      * only one copy needs to exist in binaries. */
@@ -2149,7 +2151,22 @@ static int mkv_write_vtt_blocks(AVFormatContext *s, AVIOContext *pb, const AVPac
     put_ebml_num(pb, track->track_num, track->track_num_size);
     avio_wb16(pb, ts - mkv->cluster_pts);
     avio_w8(pb, flags);
-    avio_printf(pb, "%.*s\n%.*s\n%.*s", id_size, id, settings_size, settings, pkt->size, pkt->data);
+    if (mkv->mode == MODE_WEBM)
+        avio_printf(pb, "%.*s\n%.*s\n", id_size, id, settings_size, settings);
+    avio_write(pb, pkt->data, pkt->size);
+
+    if (mkv->mode != MODE_WEBM && (id_size || settings_size || comment_size)) {
+        ebml_master block_additions = start_ebml_master(pb, MATROSKA_ID_BLOCKADDITIONS, 0);
+        ebml_master block_more      = start_ebml_master(pb, MATROSKA_ID_BLOCKMORE,      0);
+        /* Until dbc50f8a our demuxer used a wrong default value
+         * of BlockAddID, so we write it unconditionally. */
+        put_ebml_uint  (pb, MATROSKA_ID_BLOCKADDID, 1);
+        put_ebml_id(pb, MATROSKA_ID_BLOCKADDITIONAL);
+        put_ebml_length(pb, id_size + 1 + settings_size + 1 + comment_size, 0);
+        avio_printf(pb, "%.*s\n%.*s\n%.*s", id_size, id, settings_size, settings, comment_size, comment);
+        end_ebml_master(pb, block_more);
+        end_ebml_master(pb, block_additions);
+    }
 
     put_ebml_uint(pb, MATROSKA_ID_BLOCKDURATION, pkt->duration);
     end_ebml_master(pb, blockgroup);
-- 
2.26.2