Add instruction for registering async filter
Minor cleanup
Specify landscape in android manifest, should fix the wrong orientation issues.
Negative volume means unchanged, not error.
Fix some minor incorrect logging.
Fix sceAudioSetChannelDataLen() error codes.
Reduce locking in sceAudio.
Block audio output more correctly.

Still with the same thresholds, so hopefully it won't hurt sync.
Merge pull request #1854 from unknownbrackets/audio-minor

Improve audio blocking and some sceAudio functions
Shader simplification: Flip skinning math around. Remove a temporary from the texcoord generation code. Update ffmpeg submodule pointer.
Correct sceVaudio NIDs.

May fix #1738.
Don't overlay Vaudio with multichannel.

It seems to share living space with Output2/SRC.
Correct some error codes and init in Vaudio.

This makes Velocity at least play sound, hurray.
Merge pull request #1857 from unknownbrackets/audio-minor

Make sceVaudio actually work
Add Mersenne Twister random number generator.