Multi audio

[bhh1988]

New: Support multiple audio tracks

This commit adds support for selection of different audio tracks when
available in the manifest. It selects based on a combination of the
language and "role" of the audio track. This combination should be
unique in order to unambiguously select audio tracks - roles are made
unique by the backend, as audio0, audio1, etc.

One thing to be careful of in all this is how this interacts with
selecting HD/SD video. Previous implementation would cache the HD/SD
variant to switch to. Now, there are multiple HD variants and multiple
SD variants, because the HD stream could have different audio. Thus this
required some refactoring of how we pick the HD/SD streams, so that we
maintain the same audio stream while changing video quality. In the
process, I've also fixed a bug in how we size the video for audio-only
representations (before, the size would end up being so small that the
play button icon would leak into the controls).

[bhh1988]

Not sure if I'm allowed to do this? I feel like we should log something though...

[jeremypress]

If you consider this to be an error feel free to use console.error. I would probably remove that comment though

[bhh1988]

Done

[bhh1988]

Not so sure if this is ok to do - using -1 as sentinel value.

[jeremypress]

We would normally do null or just initialize it as undefined but if -1 makes more sense since these are numeric IDs I'm ok with that. What are other peoples thoughts on this?

[tonyjin]

-1's probably fine.

[jeremypress]

LGMT assuming its not tied to the shaka player update.

[jeremypress]

Magic Numbers

[bhh1988]

Defined as constants at top

[jeremypress]

Is this emitted by shakaplayer?

[bhh1988]

No. Settings menu emits this whenever you choose an option. Shaka player doesn't seem to emit events when you manually choose a track. Why?

[tonyjin]

When you do manage to merge this in after Shaka 2.2, please make sure to update this to the latest version at that point. Right now, it's 1.6.2

[bhh1988]

Will do

[tonyjin]

Same as above.

[tonyjin]

I like appending the unit, e.g. DEFAULT_VIDEO_WIDTH_PX

[bhh1988]

Done

[tonyjin]

-1's probably fine.

[tonyjin]

Nit: Capitalize The in The id of the video

[bhh1988]

Done

[tonyjin]

Is there a situation where the cache could be empty for media-audiotracks?

[bhh1988]

There should be no such situation, because handleAudioTrack() is only ever called after selection in Settings.js, which sets the cache as the only means of communicating to this file what audio track should be switched to.

[tonyjin]

Please space out your code more. I'd suggest a line break before let i = 0;, this.audioTracks = , and if (this.audioTracks.length > 1) {

[bhh1988]

Done

[tonyjin]

Could be simplified:

if (sdRep.videoId === null) {
    // There is only audio, no video
    this.videoWidth = DEFAULT_VIDEO_WIDTH;
    this.videoHeight = DEFAULT_VIDEO_HEIGHT;
} else {
    this.videoWidth = hdRep.width;
    this.videoHeight = hdRep.height;
    this.hdVideoId = hdRep.videoId !== sdRep.videoId ? hdRep.videoId : undefined;
    this.sdVideoId = sdRep.videoId;
}

[bhh1988]

Thanks. Also shaka 2.2.0 has an isAudioOnly() method, which I can call now instead of checking sdRep.videoId === null