I have live streams packetized into HLS with
set to true. The WebVTT manifests & segments are produced properly, however the EXT-X-TARGETDURATION value in the subtitle m3u8 is different than the duration in the rendition’s chunklist.
#EXTM3U #EXT-X-VERSION:3 #EXT-X-TARGETDURATION:15 #EXT-X-MEDIA-SEQUENCE:462 #EXTINF:11.929 subtitlechunk_leng_462.webvtt
#EXTM3U #EXT-X-VERSION:3 #EXT-X-TARGETDURATION:11 #EXT-X-MEDIA-SEQUENCE:467 #EXT-X-DISCONTINUITY-SEQUENCE:23 #EXTINF:10.01 media-ujvb74pq5_467.ts
This disparity can cause the subtitles to drift apart from the media content & is a violation of Apple’s guidlines
5.4. For live/linear content, target durations for subtitle playlists MUST be identical to other media.
I also believe this is causing issues with playback on Apple devices. When subtitles are active on an iOS device, and the HLS stream encounters an EXT-X-DISCONTINUITY flag, the video/audio stream stops, but subtitles continue to be displayed. This does not occur on the same stream with subtitles disabled.
Is there a setting available to force the WebVTT segment duration to a desired value for HLS?