[Cast] Convert MediaItem.playbackProperties.subtitles to MediaTracks

[gsavvid]

Previously, I would set the metadata like this:

val movieMetadata = MediaMetadata(MediaMetadata.MEDIA_TYPE_MOVIE)
movieMetadata.putString(MediaMetadata.KEY_TITLE, title)
movieMetadata.putString(MediaMetadata.KEY_SUBTITLE, subtitle)
movieMetadata.addImage(WebImage(Uri.parse(posterImage)))

val mediaInfoBuilder = MediaInfo.Builder(media.mediaUrl)
       .setStreamType(MediaInfo.STREAM_TYPE_BUFFERED)
       .setMetadata(movieMetadata)

player.loadItem(MediaQueueItem.Builder(mediaInfoBuilder.build()).build(), TimeUnit.SECONDS.toMillis(position))

Where MediaMetadata in the above example is com.google.android.gms.cast.MediaMetadata. Now that CastPlayer.loadItem() is deprecated, I want to replace it with Player.setMediaItem() but I can't find how to pass the same metadata to a MediaItem. I know that it accepts com.google.android.exoplayer2.MediaMetadata but this currently only has a title property.

So my question is how can I set the title, subtitle, and image to be displayed in the cast receiver app using a MediaItem?

[krocard]

Looking into the cast player extension, the non deprecated method setMediaItem converts the MediaItem to MediaInfo internally with with:

ExoPlayer/extensions/cast/src/main/java/com/google/android/exoplayer2/ext/cast/DefaultMediaItemConverter.java

Lines 59 to 70 in b100094

	MediaMetadata metadata = new MediaMetadata(MediaMetadata.MEDIA_TYPE_MOVIE);
	if (item.mediaMetadata.title != null) {
	metadata.putString(MediaMetadata.KEY_TITLE, item.mediaMetadata.title);
	}
	MediaInfo mediaInfo =
	new MediaInfo.Builder(item.playbackProperties.uri.toString())
	.setStreamType(MediaInfo.STREAM_TYPE_BUFFERED)
	.setContentType(item.playbackProperties.mimeType)
	.setMetadata(metadata)
	.setCustomData(getCustomData(item))
	.build();
	return new MediaQueueItem.Builder(mediaInfo).build();

This seems to imply that all other metadata than the title are dropped during the conversion.
@marcbaechinger, could you confirm? If so, should @gsavvid continue to use loadItem even if deprecated?

@Samrobbo, are the new metadata fields planned contain subtitle, MEDIA_TYPE and image ?
(Side note, having a MEDIA_TYPE metadata is awfully similar to AudioAttribute's contentType, we might consider merging them).

[Samrobbo]

The new metadata fields will cover a large selection of things yes. The initial change will be fairly minimal, but it will be quick and easy to expand it, and fields like those listed are common ones that will no doubt be implemented early on.

[krocard]

Thanks Sam. @gsavvid, until the new Metadata field are added, please continue to use the deprecated player.loadItem. I'm afraid your use-case was missed when we deprecated loadItem.

[marcbaechinger]

I don't think that use cases were missed, but as a library we can not know how an app want to pass arbitrary metadata. An app can add this behaviour though.

With new MediaItem.Builder().setTag(customObject) and app can set an arbitrary object as the tag. This could be a data object that includes metadata as strings or bitmaps or whatever is needed for your use case.

The CastPlayer then has a constructor that allows injection of a custom MediaItemConverter. You app can then convert that mediaItem with the custom tag into a MediaQueueItem from the cast API.

It's true that the MediaItem of ExoPlayer does not support meta data yet, and even if it does once, developers probably want or doesn't want to map this to the Cast item or override the metadata in the media with something else. For this purpose the converter approach has a default that just does the minimum but allows apps to customize this conversion.

Does this cover you use case @gsavvid?

[gsavvid]

It's true that you can't know how an app wants to pass arbitrary metadata but I'd expect that the metadata used by the Styled Media Receiver app would be supported.

Nevertheless, I ended up using the solution with the custom MediaItemConverter mentioned above by @marcbaechinger for another reason: the DefaultMediaItemConverter ignores the subtitles defined in the MediaItem so I wrote an implementation that takes care of that, too.