Webvtt subtitles in mp4 format with HLS

Hi,


We are developing a Packager and we are trying to implement HLS with webvtt subtitles in mp4 format. However the players doesn't show the vtt subtitles.


We have created HLS fmp4 segments and the video and audio is played by both edge and ipad, but the players does not present the webvtt subtitles.


Is it possible to play fmp4 webvtt segments with .M3U8 files? If so, is the manifest different, besides, the #EXT-X-MAP:URI= entry?


We also tried adding wvtt to the CODECS in the main manifest, but it made no difference.


We can send the webvtt segments and the manifests if needed.


Thanks.