[FFmpeg-user] webvtt HLS discontinuity mismatch

[Jonathan Baecker]

Hello everybody,

I would like to use this hls_flags 
"append_list+delete_segments+omit_endlist", but when I use them in 
combination with webvtt subtitle, it generate different playlists entries.

In stream.m3u8 I get a "#EXT-X-DISCONTINUITY" flag before the first 
segment, but im stream_vtt.m3u8 this flag is missing. So in my html 
video player (videojs 8) I can see the subtitle menu entry, but no 
subtitle in video.

If I add that flag also to the stream_vtt.m3u8 playlist, the subtitle 
will show in player. When no playlist contains that flag, then also.

My full ffmpeg command is:

ffmpeg -i video.mp4 -i dummy.vtt -map "0:v" -map "0:a" -map "1:s?" -c:v 
libx264 -crf 23 -x264-params keyint=50:min-keyint=25:scenecut=-1 
-maxrate 1300k -bufsize 2600k -preset faster -tune zerolatency 
-profile:v Main -level 3.1 -c:a aac -ar 44100 -b:a 128k -flags +cgop -f 
hls -hls_time 6 -hls_list_size 60 -hls_flags 
append_list+delete_segments+omit_endlist -var_stream_map 
"v:0,a:0,s:0,sgroup:subtitle,name:Deutsch,language:DE,default:YES" 
-master_pl_name master.m3u8 -hls_segment_filename live/stream-%d.ts 
live/stream.m3u8

When I remove hls_flags from ffmpeg command, then "#EXT-X-DISCONTINUITY" 
flag disappears from both playlists to, but in my use case I need hls_flags.

Is there a way to fix that?

Jonathan