MutedAudio strategy for media without audio track

[mudar]

I'm trying to concatenate multiple videos where some would be missing the audio track. Is this a feature you're planning to add to the library?
I tried some code changes, and I was able to concatenate when all files are missing the audio track (result would not have an audio track). I was also able to mute audio if the track was available in the source.
However, I was not able to create the empty buffer manually. Do you have any hints that could guide me to find the right steps. I have looked around, and didn't find any solutions similar to this.

[natario1]

I'm trying to concatenate multiple videos where some would be missing the audio track. Is this a feature you're planning to add to the library?

I feel like this should work already with the current library. What is the issue that you are having?

[mudar]

I will provide more info here, now that TrimDataSource is completed. For now I need to do some tests with v0.7.4 before sending a PR.
Testing quickly, currently there's a simple bug selecting a null track

com.otaliastudios.transcoder.demo E/Transcoder: Fatal error while transcoding, this might be invalid format or bug in engine or Android.
java.lang.NullPointerException: Attempt to invoke virtual method 'int java.lang.Integer.intValue()' on a null object reference
at com.otaliastudios.transcoder.source.DefaultDataSource.selectTrack(DefaultDataSource.java:63)
at com.otaliastudios.transcoder.engine.Engine.openCurrentStep(Engine.java:149)
at com.otaliastudios.transcoder.engine.Engine.getCurrentTrackTranscoder(Engine.java:219)
at com.otaliastudios.transcoder.engine.Engine.transcode(Engine.java:368)
at com.otaliastudios.transcoder.Transcoder$1.call(Transcoder.java:134)
at com.otaliastudios.transcoder.Transcoder$1.call(Transcoder.java:124)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1167)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:641)
at java.lang.Thread.run(Thread.java:764)

Handling the null exception was not enough. For example if file-1 has a single track (video) and file-2 has both tracks, then the concatenation result should have an empty sound track until the timestamp of file-2. What used to happen was a shift of the audio track for file-2 starting at the beginning of file-1.

[TemMax]

I faced the same problem. But I tried to transcode one video without audio track.
Version: 0.8.0

[TemMax]

I found workaround for this case.
With MediaMetadataRetriever we can extract value METADATA_KEY_HAS_AUDIO and if our video doesn't have audio track we can use TranscoderOptions.Builder#addDataSource with type == TrackType.VIDEO only and don't set AudioStrategy.

[cbernier]

@TemMax solution works but it is not an option if we try to concatenate 2 videos and one of them has an audio track: we want to keep the first audio track and extend it with a mute sound for the duration of the second video.

[cbernier]

I submitted a pull request to solve @TemMax workaround: https://github.com/natario1/Transcoder/pull/61

@natario1 The next thing that we would like the library to handle is to optionally fill the missing track sources by a mute sound and maybe even a black image for the missing video sources.