Enable multiple video tracks with no audio.

[cbernier]

There's always a number of audio sources equal to the number of video sources (TranscoderOptions.java:131)
and getTrackFormat returns null when the video file had no audio track or vice versa.
So when getTrackFormat returns null for all sources we can remove the associated track
type.

If only some of the data source files have no audio or video sources then it will still throw
an exception because we can't build a valid stream with missing parts.: it is either a full
track or no track.

[cbernier]

If only some of the data source files have no audio or video sources then it will still throw
an exception because we can't build a valid stream with missing parts.: it is either a full
track or no track.

I am currently looking to fix this exception for the audio track by filling the missing parts with a muted sound: https://github.com/natario1/Transcoder/issues/51#issuecomment-587570954

[natario1]

Thanks @cbernier2 ! Wouldn't TrackStatus.ABSENT be a better choice? Literally none of the input file have this track type so... I'd say it's absent. It would also be consistent with the single file case.

[cbernier]

Thanks @cbernier2 ! Wouldn't TrackStatus.ABSENT be a better choice? Literally none of the input file have this track type so... I'd say it's absent. It would also be consistent with the single file case.

Yes, indeed, I change that.

[natario1]

Thanks!