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How to mix AMR files ?

Started by horiaciu June 27, 2007
Hello,

I am implementing a simple mixing program (i.e. create a new sound
file combinig two initial files - all the same format). I have
implemented this for WAV files (PCM) and now I want to support AMR. I
can do this in 2 ways:

1. convert to PCM and reuse the mixing code - I cannot find any
documentation on how to convert an AMR frame to PCM samples. What
happens after I reorder the bits and obtain the 3 classes (A, B and
C) ?

2. directly mix 2 AMRs frame by frame - I have no ideea how to do this.

Any help is welcome,
Thanks

Horia
To my limitted knowledge, direct mixing of 2 signals in coded domain
is some what impossible. The best I think one can hope for is
skipping the post filtering at the decoders.

--- In s..., "horiaciu" wrote:
>
> Hello,
>
> I am implementing a simple mixing program (i.e. create a new sound
> file combinig two initial files - all the same format). I have
> implemented this for WAV files (PCM) and now I want to support AMR.
I
> can do this in 2 ways:
>
> 1. convert to PCM and reuse the mixing code - I cannot find any
> documentation on how to convert an AMR frame to PCM samples. What
> happens after I reorder the bits and obtain the 3 classes (A, B and
> C) ?
>
> 2. directly mix 2 AMRs frame by frame - I have no ideea how to do
this.
>
> Any help is welcome,
> Thanks
>
> Horia
>