Accessing active datasource in onPositionDiscontinuity

[Tolriq]

[REQUIRED] Searched documentation and issues

I did :)

[REQUIRED] Question

I'm having an hard time to get the active datasource when the media change in a ConcatenatingMediaSource.

I use a specific DataSourceFactory that extends HttpDataSource.BaseFactory and prepare the media in the open(dataSpec).
During this preparation the media can be transcoded or not and depending on many factor the resulting may support some things like seeking or not.
I need to be able to access this information to do things like not calling normal seek but restart the transcoding at the new position.

The problem is that in ConcatenatingMediaSource open can be called to prepare the next media while the active media is still not closed.

So the question is how can I access the datasource from the player onPositionDiscontinuity callback. Or how can I access the MediaSource from the DataSource to be able to modify the tag?

[AquilesCanta]

Why don't you assign a specific DataSourceFactory to each MediaSource so that each DataSourceFactory knows to which MediaSource they are assigned?

So when the media source calls open(...) for preparation (or whatever), you know which is the calling MediaSource, since the DataSourceFactory knows the corresponding MediaSource.

[Tolriq]

Isn't that highly inefficient to create a DefaultDataSourceFactory and my factory for every single items for very large playlists?

[tonihei]

DefaultDataSourceFactory is just a thin wrapper creating other DataSource instances, so there should be no issue with creating multiple factories if needed.

Not sure about your exact use case, but you can also consider one of the following:

• Use ResolvingDataSource to add additional loading steps based on the DataSpec. You could detect whatever you need from the DataSpec URL, custom header key-value pairs or from using the customData object. Whether this is easily possible depends on the details of what you need and what you are trying to achieve.
• Set a tag on each MediaSource (or MediaItem) that can be retrieved by Player.getCurrentTag() in onPositionDiscontinuity.

[Tolriq]

@tonihei Ok so let me try to better explain the need that is.

The player can play media from many different sources and some of them can transcode the media on the fly.
The transcoding or not decision is made at the DataSource.open to avoid wasting server resources.
When transcoding some server for some media type and transcoded media can generate non seekable media via normal player seek functions.
I can detect and know this only when transcoding start so in DataSource.open

But I need to know this at the player / UI side to either disable the seek functions or intercept the seek to be actual restart of the media at the proper new starting point.

The problem is that with gapless / ConcateningMediaSource the DataSource.open is called independently of the active media.

And from DataSource.open I can't access the corresponding MediaItem/MediaSource to update the tag that I could then use in onPositionDiscontinuity

So TL;DR I need to access the MediaSource/MediaItem from the DataSource.open not sure ResolvingDataSource brings anything here as it's before the open.

[tonihei]

ResolvingDataSource is essentially just an easy wrapper to intercept the DataSpec to the DataSource. If the actual information you need is only available afterwards, you would probably need to follow @AquilesCanta's advice and use a DataSource.Factory for each of your DataSources that has access to your tag object:

MediaSource mediaSource = 
    new ProgressiveMediaSource.Factory(() -> new MyCustomDataSource(tag))
      .setTag(tag)
      .createMediaSource(MediaItem.forUri(uri));

Aside: If you make the tag object mutable be aware that the loading takes place on another thread, so you need additional thread safety around the updates.

[Tolriq]

Thanks that's what I do, but the new playlist api is all about MediaItem directly no? Or I can use MediaSources directly and still use the new playlist api instead of concateningmediasource?

[tonihei]

Yes, you can. The ExoPlayer interface defines all relevant methods for that (e.g. setMediaSource, addMediaSource etc)

[Tolriq]

Ok thanks, closing this one too as there's no other way and factory are small :)