Replace gapless playback with skip silence

[naveensingh]

Since exoplayer transitions between media items as seamlessly as possible, we don't need a switch for it (it works as well as the previous MediaPlayer.setNextMediaPlayer implementation). The skip silence feature trims any silence in the audio stream, not just at the start/end hence putting gapless playback there is a little misleading.

If we don't want to add such a feature, we can remove the preference and category.

Sidenote: True gapless playback (absolutely zero gaps) is possible in exoplayer but we don't really want to complicate things using concatenated media sources.

[tibbi]

from the users perspective Skip silence makes no sense, lets keep the old string even if you change the functionality

[naveensingh]

Yes, that was the plan. I added skip silence as an extension of gapless playback but then I realized this problem:
The skip silence feature trims any silence in the audio stream, not just at the start/end

That means when playing some music with a tune like SILENCE_DRUM_SILENCE_DRUM_SILENCE, the silent part is always skipped (including the one in the middle) and that's not a feature of gapless playback. I wasn't actively researching or trying to tweak it but there is a related open issue: google/ExoPlayer#7423

We have the following options then:

• Keep the preference named Gapless playback and wait for user feedback.
• Disable skip silence, convert the gapless playback preference to a dummy preference that does nothing and it is there just so old users aren't confused. (It also kinda of advertises that this app supports gapless playback and we might wanna keep it that way)
• Disable skip silence, remove the gapless preference, and add "Enable gapless playback by default" in the release changelog.

[naveensingh]

The skip silence feature trims any silence in the audio stream, not just at the start/end

Please ignore my previous comment, I'm gonna fix this instead of renaming the preference

[naveensingh]

New PR here: #595
I'll close this one.

[naveensingh]

Closed in favor of #595