feat!: Add support for OTF format streams

[absidue]

Description

Some videos have formats that are a bit different than other ones, YouTube seems to refer to these as OTF. According to NewPipeExtractor (https://github.com/TeamNewPipe/NewPipeExtractor/blob/dev/extractor/src/main/java/org/schabi/newpipe/extractor/services/youtube/DeliveryType.java#L23-L38) these can occur on videos with low view counts and live stream replays that have just been reencoded to normal videos. Instead of allowing you to request arbitrary chunks with the range query parameter, instead you use the sq query parameter to request sequences, the first sequence (&sq=0) contains the duration of the sequences, so we need to request it while building the DASH manifest.

This implementation was inspired by the NewPipeExtractor implementation, so big thanks to them :).

Here is a video with OTF streams: https://www.youtube.com/watch?v=DJ8GQUNUXGM
The 720p and 360p streams are normal, the other ones (144p, 240p and 480p) are OTF streams

⚠️ Breaking change ⚠️

The toDash functions are now asynchronous, they return a Promise<string> instead of a string, as we need to fetch the first sequence while building the manifest.

Type of change

Please delete options that are not relevant.

• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have checked my code and corrected any misspellings

for release please:

BEGIN_COMMIT_OVERRIDE
feat!: Add support for OTF format streams

BREAKING CHANGE: The toDash functions are now asynchronous, they now return a Promise<string> instead of a string, as we need to fetch the first sequence of the OTF format streams while building the manifest.
END_COMMIT_OVERRIDE

[absidue]

Okay so apparently videos with OTF streams have the dash url field populated, so we don't need to generate these manifests in YouTube.js.

[LuanRT]

I just tested this and also the dash manifest YouTube returns and both work great. This could be useful for those who need to filter out unwanted formats.

[absidue]

Yep, just remembered that FreeTube can't use YouTube's one because, videojs-http-streaming (the part of video.js that handles DASH) only supports MP4-DASH, it doesn't support WebM-DASH.