Rendition report is not used when switching

[kanongil]

The feature in #3125 does not seems to work.

What version of Hls.js are you using?

master / c5698be.

What browser and OS are you using?

macOS Chrome

Test stream:

https://stream.sob.m-dn.net/live/sb1-ll/index.m3u8

Checklist

• The issue observed is not already reported by searching on Github under https://github.com/video-dev/hls.js/issues
• The issue occurs in the stable client on https://hls-js.netlify.com/demo and not just on my page

• The issue occurs in the latest client on https://hls-js-dev.netlify.com/demo and not just on my page

• The stream has correct Access-Control-Allow-Origin headers (CORS)
• There are no network errors such as 404s in the browser console when trying to play the stream

Steps to reproduce

1. Play the stream.
2. Change the level.

Expected behavior

Request the new level playlist using blocking playlist request using the msn and part info from the rendition report.

Actual behavior

Request the new level playlist without msn & part params, followed by another request with msn & part.

[robwalch]

Please provide more details on how you are changing the level.

Rendition reports are only used when these conditions are met:

• the other level has never loaded
• the current playlist response was from a blocking playlist request

Have a look at switchParams in the source and when testing.

[kanongil]

It appears that this is because it fails to actually match the URI here:

hls.js/src/controller/base-playlist-controller.ts

Line 67 in f3e2e99

if (uri === playlistUri.substr(-uri.length)) {

The current logic only works if the media playlists are all in the same url location, or are absolute urls.

Eg. it fails for the stream I linked, where it can contain reports like these:

#EXT-X-RENDITION-REPORT:URI="../vNG7t017KgCd93d8y3HxGjR/stream.m3u8",LAST-MSN=329899,LAST-PART=2
#EXT-X-RENDITION-REPORT:URI="../v2-2y65rygQ0kZW3a5-WWyJ/stream.m3u8",LAST-MSN=329899,LAST-PART=2
#EXT-X-RENDITION-REPORT:URI="../vwj1H8QkVzPcbycrRtI1EJw/stream.m3u8",LAST-MSN=329899,LAST-PART=2
#EXT-X-RENDITION-REPORT:URI="../vL2LFCVuQXAXxUgh4c12Ilh/stream.m3u8",LAST-MSN=329899,LAST-PART=2
#EXT-X-RENDITION-REPORT:URI="../v8Ew9fFqC0AEwfHoR5PS1cF/stream.m3u8",LAST-MSN=329899,LAST-PART=2

[kanongil]

This actually uncovers another issue, which is that hls.js just ignores the apparently missing report, and trudges ahead anyway. I would expect some kind of warning / error, and possibly a downgrade to non-low-latency streaming.

After all, valid rendition reports are a required component of low-latency streams: https://tools.ietf.org/html/draft-pantos-hls-rfc8216bis-08#appendix-B.1

Each Media Playlist contains one EXT-X-RENDITION-REPORT tag for
each Media Playlist (Rendition) in the Master Playlist, except for
the Media Playlist to which the EXT-X-RENDITION-REPORT tag is
being added, and Playlists that contain the EXT-X-I-FRAMES-ONLY
tag.