Crash in `TextRenderer` when rendering stream with single subtitle

[baconz]

[REQUIRED] Issue description

We get an NPE in 2.12.0 when the TextRenderer tries to render a stream with a single subtitle:

     Caused by: java.lang.NullPointerException: throw with null exception
        at com.google.android.exoplayer2.util.Assertions.checkNotNull(Assertions.java:147)
        at com.google.android.exoplayer2.text.TextRenderer.getNextEventTime(TextRenderer.java:328)
        at com.google.android.exoplayer2.text.TextRenderer.render(TextRenderer.java:201)
        at com.google.android.exoplayer2.ExoPlayerImplInternal.doSomeWork(ExoPlayerImplInternal.java:892)
        at com.google.android.exoplayer2.ExoPlayerImplInternal.handleMessage(ExoPlayerImplInternal.java:467)
        at android.os.Handler.dispatchMessage(Handler.java:101) 
        at android.os.Looper.loop(Looper.java:164) 
        at android.os.HandlerThread.run(HandlerThread.java:65) 

I think this was introduced with the null checks added here: 0efec5f#diff-2a869b1d2a8dabec5def4e6e02d2bd18

It is possible to call getNextEventTime() on the first render() if nextSubtitle.isEndOfStream().

[REQUIRED] Reproduction steps

It is difficult for us to share a stream in the clear that reproduces this.

[REQUIRED] Link to test content

See above.

[REQUIRED] A full bug report captured from the device

Happy to do this upon request.

[REQUIRED] Version of ExoPlayer being used

2.12.0

[REQUIRED] Device(s) and version(s) of Android being used

Any

[icbaker]

I'm not able to reproduce this crash.

I tried with the following WebVTT file:

WEBVTT

00:00.000 --> 00:01.234
This is the first subtitle.

And played it in the demo app at 2.12.0 using this JSON snippet:

{
  "name": "go/exoghi/8017",
  "uri": "https://storage.googleapis.com/exoplayer-test-media-1/gen-3/screens/dash-vod-single-segment/video-avc-baseline-480.mp4",
  "subtitle_uri": "file:///sdcard/Download/webvtt.vtt",
  "subtitle_mime_type": "text/vtt",
  "subtitle_language": "en"
}

The video played fine and displayed the subtitle as expected on the screen. I didn't see any suspicious stack traces in logcat.

Are you able to reproduce the behaviour you see in the ExoPlayer demo app?

Can you provide more info about your setup to help us reproduce and investigate?

[baconz]

Indeed I can't repro with the VTT example you posted. I suspect it is because the VTT input buffer does not set BUFFER_FLAG_END_OF_STREAM on the first pass.

I am able to reproduce reliably with the CEA-608 subtitles in the example below. Here, the very first time the decoder grabs captions, the input buffer has BUFFER_FLAG_END_OF_STREAM set, and thus it triggers the NPE code path.

      {
        "name": "bad cea-608 dash",
        "uri": "https://static-us-east-2-fastly-a.www.philo.com/storage/dev/seth/exo_cc_npe/manifest.mpd"
      },

[icbaker]

Thanks, I can repro with that media.

(side note, I had to tweak the URL slightly, think it should be https://static-us-east-2-fastly-a.www.philo.com/storage/dev/seth/exo_cc_npe/manifest.mpd - I've edited your comment to help anyone else trying to repro)

[icbaker]

I've sent a fix for this - thanks for reporting