Closed Captions in Media3

[zhoushsong]

The Closed Caption track cannot be read in Media3 Player.
Could you please check what the issue is?

Using this method, I can only read the audio and video tracks

 Tracks xx =  player.getCurrentTracks();
        for (int i = 0; i < xx.getGroups().size(); i++) {
            int trackType = xx.getGroups().get(i).getMediaTrackGroup().type;
            if (trackType == C.TRACK_TYPE_TEXT) {
                textTrackGroups.add(xx.getGroups().get(i).getMediaTrackGroup());
            }
        }

Below is the video link.
http://www.melodvb.com/test/cc.mp4

[oceanjules]

Have you tried adding it to https://github.com/androidx/media/blob/release/demos/main/src/main/assets/media.exolist.json to see the error?

• When I put the above URL, I get a snackbar exception "cleartext http traffic not permitted"
• When I try to change the above URL to https, I get androidx.media3.datasource.HttpEngineDataSource$OpenException: android.net.http.NetworkExceptionWrapper: Exception in CronetUrlRequest.

Unfortunately, I can see that the exception disappears too fast and you can't actually see the full text to realise there is a URL to follow:

media/libraries/datasource/src/main/java/androidx/media3/datasource/HttpDataSource.java

Lines 385 to 393 in 7cc1056

	public CleartextNotPermittedException(IOException cause, DataSpec dataSpec) {
	super(
	"Cleartext HTTP traffic not permitted. See"
	+ " https://developer.android.com/guide/topics/media/issues/cleartext-not-permitted",
	cause,
	dataSpec,
	PlaybackException.ERROR_CODE_IO_CLEARTEXT_NOT_PERMITTED,
	TYPE_OPEN);
	}

Please read https://developer.android.com/guide/topics/media/issues/cleartext-not-permitted to see how you could overcome this issue.

[icbaker]

I can reproduce what you observe when playing the provided URL in the demo app with cleartext traffic allowed. I see a video and audio track, but no text track:

tracks [eventTime=7.28, mediaPos=0.00, window=0, period=0
  group [ id=0
    [X] Track:0, id=1/211, mimeType=video/avc, container=video/mp2t, codecs=avc1.640028, res=1280x720, color=NA/NA/NA/8/8, supported=YES
  ]
  group [ id=1
    [X] Track:0, id=1/221, mimeType=audio/mp4a-latm, container=video/mp2t, codecs=mp4a.40.2, channels=2, sample_rate=48000, language=und, supported=YES
  ]
]

I tried to curl the file to analyse it offline but I got an HTML 403 error page.

I tried opening the link in my browser to download it, but that also failed (just buffered forever).

I tried passing the URL to https://gpac.github.io/mp4box.js/test/filereader.html and that also failed with

downloader.js:143 Mixed Content: The page at 'https://gpac.github.io/mp4box.js/test/filereader.html' was loaded over HTTPS, but requested an insecure XMLHttpRequest endpoint 'http://www.melodvb.com/test/cc.mp4'. This request has been blocked; the content must be served over HTTPS.

Please provide or host the file in a way that we can easily download it and we can inspect it further to understand why ExoPlayer doesn't find a text track.

[zhoushsong]

Hello, thank you for your help. This video has closed captions. You can copy this link and play it in PotPlayer or VLC, or open the link in Google Chrome, then right-click and select "Save as" to download the video locally for testing.

[icbaker]

This file has an MP4 file ending, but it's actually an MPEG-TS file (so handled by ExoPlayer's TsExtractor, not Mp4Extractor).

I believe this file doesn't contain enough metadata for ExoPlayer to identify the subtitle tracks.

I made subtitles appear by configuring them manually in the demo app's PlayerActivity:

media/demos/main/src/main/java/androidx/media3/demo/main/PlayerActivity.java

Line 321 in 7cc1056

return new DefaultMediaSourceFactory(/* context= */ this)

return new DefaultMediaSourceFactory(
        /* context= */ this,
        new DefaultExtractorsFactory()
            .setTsSubtitleFormats(
                ImmutableList.of(
                    new Format.Builder()
                        .setSampleMimeType(MimeTypes.APPLICATION_CEA608)
                        .setAccessibilityChannel(0)
                        .build()))

I tried other values of setAccessibilityChannel. I see subtitles with 1, but not 2 or 3. This is consistent with the Closed captions 1/2/3/4 tracks exposed by VLC (1 & 2 have subtitles visible, 3 & 4 don't). I suspect VLC is just configuring all 4 possible subtitle tracks and exposing them, whether they are contained in the file or not. You can replicate this behaviour in ExoPlayer using the code snippet above.