avformat: add subtitle support in master playlist m3u8

Test with the following command for the webvtt subtitle:
$ ./ffmpeg -y -i input_with_subtitle.mkv \
 -b:v:0 5250k -c:v h264 -pix_fmt yuv420p -profile:v main -level 4.1 \
 -b:a:0 256k \
 -c:s webvtt -c:a mp2 -ar 48000 -ac 2 -map 0:v -map 0:a:0 -map 0:s:0 \
 -f hls -var_stream_map "v:0,a:0,s:0,sgroup:subtitle" \
 -master_pl_name master.m3u8 -t 300 -hls_time 10 -hls_init_time 4 -hls_list_size \
 10 -master_pl_publish_rate 10  -hls_flags \
 delete_segments+discont_start+split_by_time ./tmp/video.m3u8

Check the master m3u8:
$ cat tmp/master.m3u8
#EXTM3U
#EXT-X-VERSION:3
#EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID="subtitle",NAME="subtitle_0",DEFAULT=YES,URI="video_vtt.m3u8"
#EXT-X-STREAM-INF:BANDWIDTH=6056600,RESOLUTION=1280x720,CODECS="avc1.4d4829,mp4a.40.33",SUBTITLES="subtitle"
video.m3u8

Check the result by convert to mkv:
$ ./ffmpeg -strict experimental -i ./tmp/master.m3u8 -c:v copy -c:a mp2 -c:s srt ./test.mkv

Signed-off-by: Limin Wang <lance.lmwang@gmail.com>

1 files changed, 16 insertions, 1 deletions

diff --git a/libavformat/hlsplaylist.c b/libavformat/hlsplaylist.c
index 56244496c0..43f9d281ba 100644
--- a/libavformat/hlsplaylist.c
+++ b/libavformat/hlsplaylist.c
@@ -48,9 +48,22 @@ void ff_hls_write_audio_rendition(AVIOContext *out, char *agroup,
     avio_printf(out, "URI=\"%s\"\n", filename);
 }
 
+void ff_hls_write_subtitle_rendition(AVIOContext *out, char *sgroup,
+                                  const char *filename, char *language, int name_id, int is_default) {
+    if (!out || !filename)
+        return;
+
+    avio_printf(out, "#EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID=\"%s\"", sgroup);
+    avio_printf(out, ",NAME=\"subtitle_%d\",DEFAULT=%s,", name_id, is_default ? "YES" : "NO");
+    if (language) {
+        avio_printf(out, "LANGUAGE=\"%s\",", language);
+    }
+    avio_printf(out, "URI=\"%s\"\n", filename);
+}
+
 void ff_hls_write_stream_info(AVStream *st, AVIOContext *out,
                               int bandwidth, const char *filename, char *agroup,
-                              char *codecs, char *ccgroup) {
+                              char *codecs, char *ccgroup, char *sgroup) {
 
     if (!out || !filename)
         return;
@@ -71,6 +84,8 @@ void ff_hls_write_stream_info(AVStream *st, AVIOContext *out,
         avio_printf(out, ",AUDIO=\"group_%s\"", agroup);
     if (ccgroup && ccgroup[0])
         avio_printf(out, ",CLOSED-CAPTIONS=\"%s\"", ccgroup);
+    if (sgroup && sgroup[0])
+        avio_printf(out, ",SUBTITLES=\"%s\"", sgroup);
     avio_printf(out, "\n%s\n\n", filename);
 }