Audio playback improvement

[kumama]

Hi, popcormmix,

As reported long long time ago( #28 ), a problem about audio channel change during playback.

Some container format doesn't care about audio channels, so we should check decoded(codec output) audio format.(As ffmpeg do) And this audio format change is minor change, so we don't need close -> open codec.

I know this patch is very rough and need some improvement.

May I ask you reviewing this patch?

[popcornmix]

Do you have a test file that has a changing number of audio channels?

[kumama]

• about fdk-aac

Watching video with omxplayer I noticed we can hear some cycle noises during playback sometimes. It's not always and not big. Some month ago I can't stand this noise, check video file using vlc(on my mac) but it's normal.So I debug omxplayer but noting is here. Then I convert aac to pcm using ffmpeg and visualize.

Using ffmpeg internal aac decoder ->

Using fdk-aac decoder ->

obviously ffmpeg's internal aac decoder generate cyclic noise.so I trying to use fdk-aac.The noise is gone.

BUT, some reason, I think it should not become default in this time.

• ffmpeg's fdk-aac wrapper's implementation have missing part(e.g.: channel change ... ),
• fdk-aac license
• Need work Makefile.ffmpeg

CPU usage is fair. when compile fdk-aac with same compiler optimization option.

[kumama]

I have the file that has a changing number of audio channels.
Please mail me. ( kuwana at kuwana.org ), I'll send you a URL.

Buffer allocation is annoying thing.I know the normal way is freeing buffer and re-allocate appropriate size. but the buffer is tunneled, so some buffer is using by another component and can't free.so at this time allocate max size of buffer for further channel change.

[kumama]

I made channel change sample.
http://kumama.org/omxplayer/channel_transition.ts

[Ruffio]

@kumama will you fix the conflicts?

[Ruffio]

@popcornmix Can this be merged?