Question about AudioMixer

[jcbo...@gmail.com]

Hi.

 

I'm Android Developer.

 

I have some questions about AudioMixer of Android AudioFramework.

 

When Mixing audio frames sample by sample,

 

In theory, Overflow can be occurred.

 

Because size of sample is 16bit size , so 32bit outTemp buffer is used in AudioMixer.cpp

 

But, Tracks can be max 32 tracks, so It can be the range of

 

-32*4096*32767 ~ 32(max number of tracks)*4096(volume max value)*32767(sample max valume).

 

But 32bit signed pcm can be ranged of -16*4096*32767 ~ 16*4096*32767.

 

So 16*4096*32767 ~ 32(max number of tracks)*4096(volume max value)*32767(sample max valume) or -32*4096*32767~ -16*4096*32767 range occur overflow.

 

I want know the reason that how come the outTemp buffer size is 32bit, and

 

When the integer volume range is 0~ 2048 ,or outTemp buffer size is 64bit, the overflow does not occur.

 

Please reply the question.

 

Thanks,

[Glenn Kasten]

You are correct, it is possible to overflow / clip if there are too many active tracks at a high volume.