Request playlist with part 0

[kanongil]

Is your feature request related to a problem? Please describe.

When hls.js requests low latency playlist updates using blocking, it doesn't properly advance the msn and part when a segment is complete. Instead it requests a non-existing future part, and relies on the server to handle it (as it should per spec).

Describe the solution you'd like

When a playlist update indicates that a segment is complete (when the final segment contains a duration and url), advance the next update msn and set part to 0.

Describe alternatives you've considered

Keep it as is. This is a valid way to do it, but it reduces potential caching benefits in the CDN.

[robwalch]

Great suggestion!

Hopefully, playlist updates publish the last part and EXTINF duration and URL at the same time. I got mixed results with the sample streams I've been testing with. Knowing when we have the last part and can expect new parts would be really useful, and we can simply check part.fragment.relurl to determine if the parent fragment is complete.

[robwalch]

Here are links to the implementation:

https://github.com/video-dev/hls.js/blob/v1.0.0-rc.4/src/controller/base-playlist-controller.ts#L140
up to this.loadPlaylist(new HlsUrlParameters(msn, part, skip));

[robwalch]

and lastPartIndex getter:

hls.js/src/loader/level-details.ts

Line 116 in 25db4d7

get lastPartIndex(): number {

[robwalch]

Fix in pending PR: https://deploy-preview-3784--hls-js-dev.netlify.app/demo/