Parse Subtitles During Extraction BUG

[FongMi]

Version

Media3 1.5.1

More version details

This video file can't not play after 1.4.0-alpha02
1.4.0-alpha01 can play well even if have error.
https://drive.google.com/file/d/18fYNCarTAbN84679hBS_KKobqRDWKlir/view?usp=drive_link

textTrackTranscodingEnabled need to set false
parseSubtitlesDuringExtraction need to set false
legacyDecodingEnabled need to set true

The above settings can be made to play in 1.5.1

Devices that reproduce the issue

Xiaomi 13

Devices that do not reproduce the issue

None

Reproducible in the demo app?

Yes

Reproduction steps

1. add file path to media.exolist.json

Expected result

Play well

Actual result

See error

Media

https://drive.google.com/file/d/18fYNCarTAbN84679hBS_KKobqRDWKlir/view?usp=drive_link

Bug Report

• You will email the zip file produced by adb bugreport to android-media-github@google.com after filing this issue.

[icbaker]

Actual result

See error

What is the error?

[FongMi]

1.4.0-alpha01 can see the error too, but can play video.
1.4.0-alpha02~1.5.1 can see the error and stop play.

[icbaker]

This looks like a duplicate of #1722

Can you please try with 1.6.0-alpha01?

[FongMi]

1.6.0-alpha01 is same. not play continued

[icbaker]

Thanks - the changes in #1722 don't work here because the exception takes down the whole MatroskaExtractor and its Loadable, not just a Loadable being used only for subtitle playback.

Playback of your broken video can be permitted by adding try / catch (RuntimeException) around the call to parse here:

media/libraries/extractor/src/main/java/androidx/media3/extractor/text/SubtitleTranscodingTrackOutput.java

Lines 146 to 151 in 76088cd

	currentSubtitleParser.parse(
	sampleData,
	sampleStart,
	size,
	SubtitleParser.OutputOptions.allCues(),
	cuesWithTiming -> outputSample(cuesWithTiming, timeUs, flags));

But I'm not sure the best way to signal that error out of the player in a programmatically visible, non-fatal way (rather than just logging it and continuing) - for consistency with the way we handle other subtitle parsing errors.

[icbaker]

Digging a bit further into the provided file, it has a cue that starts like this (i.e. has duration zero):

Dialogue: 0:00:00:00,0:00:00:00

The cue looks like it contains some conversion metadata, and is not intended to be displayed.

This currently trips up some fiddly logic in SsaParser that's designed to support overlapping subtitles (see google/ExoPlayer#6595), and results in it creating a single, empty, cue list - which then violates the assumption that every SSA cue line results in at least two lists of cues, one containing the text and another containing no cues (to signal the end), which ends up throwing the exception you're seeing.

I've got a change in review which fixes playback for your file by just ignoring cues where startTimeUs >= endTimeUs as invalid.

I'm also looking at submitting a change that suppresses+logs all parsing errors that bubble out as far as SubtitleTranscodingTrackOutput as described above - in order to maintain parity with 'legacy' subtitle decoding (where errors that bubble out this far are suppressed and logged in TextRenderer).

[FongMi]

Thank you for your hard testing.