Use yt_dlp.get_postprocessors()

[tcely]

Fixes #412 #645

[meeb]

Looks reasonable to me.

I realise the media item instance isn't passed to download_media(...) but that string check could match if the video title contains (for example) av1- for some reason, however unlikely that might be.

Perhaps the media item instance should be passed to download_media(...)? Then you could use the actual codec match from media.source..... This could also simplify the args for download_media(...) which have grown quite a lot lately. I think in very early drafts download_media(...) was called in a worker that couldn't be passed a media instance without an extra lookup but that seems pretty moot now given it's called from where a media instance is already created.

I'm pretty sure download_media(...) is only called in two places so it's not a massive refactor, once in models.py as download_youtube_media(...) and once in signals.py if I remember. Both can just have self or instance added as the first arg most likely.

[tcely]

Refactoring it would be a good idea. Especially when we start asking for yt-dlp to select the format for us.

I'd like to get away from passing a format and handling fallbacks, if possible.

[meeb]

Thanks!