How to enable subtitles on a hls file from Google Cast sender app

Question

Is it possible to enable subtitles from a Google Cast sender app? I have implemented Google Cast in my app and hls streaming is working fine on Chrome Cast. There is a subtitle track included in the hls file, but the subtitles are not showing. There are no .vtt files available for the videos and therefor I cannot implement MediaTrack to send subtitles URL to receiver app. I was wondering if it is possible to enable subtitles on the hls streaming from sender app or do I need to make a custom receiver app for that?

I am creating the MediaInfo object which is sent to receiver app in the following way (standard)

private MediaInfo buildMediaInfo() {
        MediaMetadata movieMetadata = new MediaMetadata(MediaMetadata.MEDIA_TYPE_MOVIE);

    movieMetadata.putString(MediaMetadata.KEY_TITLE, mTitle + " (" + mProdYear + ")");
    movieMetadata.putString(MediaMetadata.KEY_SUBTITLE, mFilmType);
    movieMetadata.addImage(new WebImage(Uri.parse(mImageUrl)));

    return new MediaInfo.Builder(mVideoUrl.toString())
            .setStreamType(MediaInfo.STREAM_TYPE_BUFFERED)
            .setContentType("videos/mp4")
            .setMetadata(movieMetadata)
            //enable subtitles on hls streaming??
            .build();
}

Answer 1

You didn't mention what receiver you are using. In Default/Styled receiver, HLS (adaptive streams in general) are handled by the Media Player Library. If it sees a supported tracks, then that information will be sent to the connected devices in status updates. Sender apps can then learn about the presence of additional tracks (and their associated track ids) and then can turn them on or off. For example, if you use CCL, this will be handled for you automatically (on the sender side): to see that in action, grab CastVideos-android-v2 (which uses CCL) and have two phones, connection to the receiver and start one of the first three movies there (the first three have closed captions) and go to the full screen cast controller page and turn on closed caption and select the text track. Then connect the second phone to the same receiver and you'll see it syncs up with what is playing on the receiver and if you go into the full screen controller on the second phone, you'll see that it knows about the closed captions and what track is enabled.