Synchronization not working for HLS VOD content

[forbjok]

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Website Problem

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Description of the Problem

Using a HLS-encoded VOD video (.m3u8 manifest pointing to either fragmented mp4 segments or single file w/ byte ranges), the stream does not synchronize between users. Pausing/unpausing or seeking as leader does not cause other users' state/position to be updated, and refreshing will always cause the video to restart from the beginning instead of synchronizing to the leader's position.

I would expect this to synchronize like any other video file. I know for a fact that this is possible, as I have implemented the same functionality myself in a personal project using the same player component (video.js) as cytube uses.

Here's an example video that reproduces this issue: https://junk.forbstuff.net/t3mp/cytube-hlsvod-repro/master.m3u8

I suspect a possible cause is that cytube is coded to always consider HLS links as a livestream (It says "Currently Playing: Livestream" over the video), which would not be controllable, however if this is the case, it's not a sound assumption, as HLS can also be used for non-live pre-encoded, fully seekable video (VOD), as is the case here.

System Information

OS: Windows 11
Web Browsers tested: Chrome, Brave, Firefox, Edge

There are no relevant error messages, and nothing new shows up in the console when pausing/unpausing or seeking on either the leader or the viewer browsers.

[calzoneman]

All directly added m3u8s are treated as livestreams and are therefore not synced.

See #767 -- someone contributed support for HLS VODs via the custom-media target (therefore relying on the JSON manifest to specify whether it is live or not), but it was not implemented for directly adding m3u8s (see #767 (comment) for why -- it's difficult to programmatically decide whether a given m3u8 link represents a livestream or a VOD because the format itself is designed for livestreaming).