feat(DASH): Add support for service descriptions

[adgllorente]

Changes

• Parse ServiceDescription from Manifest
• Use ServiceDescription for live syncrhonization

Doubts

• I have added support for just one ServiceDescription. Low Latency spec seems that it supports more than one. If this support is mandatory, how can I know which ServiceDescription should I use?
• I am executing onTimeUpdate when this.manifest_.serviceDescription OR this.config_.streaming.liveSync, should it be an AND?

[avelad]

@adgllorente

Doubts

I have added support for just one ServiceDescription. Low Latency spec seems that it supports more than one. If this support is mandatory, how can I know which ServiceDescription should I use?

Let's just take the first one, it's the same as we do with the trickplay track.

I am executing onTimeUpdate when this.manifest_.serviceDescription OR this.config_.streaming.liveSync, should it be an AND?

We don't want to break the old configuration, so OR is perfect in this case.

[adgllorente]

@avelad

I have parsed many values from Latency and PlaybackRate but we are using just 2 of them, do you agree in removing others?

[avelad]

@avelad

I have parsed many values from Latency and PlaybackRate but we are using just 2 of them, do you agree in removing others?

In the context of this PR, yes.

[avelad]

@adgllorente I forgot to comment before, add a parsing test of these new parameters in dash_parser_manifest_unit.js

[github-actions]

Incremental code coverage: 63.46%

[avelad]

LGTM. I'll wait to pass all tests to merge it. Thanks for your contribution!