asterisk users - Mar 2013 - Disagreements between codec_siren14 and Polycom sources

There appears to be a disagreement between the encoding given in the
sources for Siren14 that are downloaded from Polycom (and the ITU, both
are the same) and that implemented by codec_siren14.so.  The latter
agrees with the actual device.

If I make a .sln32 file and run the encoder from ITU/Polycom with

	encode 0 foo.sln32 foo.siren14 48000 14000

the resulting file doesn't play back correctly with the Digium's siren14
codec.  I know the parameters are correct because the file is the same
size as that made by the Digium codec.

Both sets of decoders/encoders (Digium and Polycom/ITU) are symmetric and
can decode what they encode, but neither can read the encoding of the other.

Is there some subtle difference between G.722.1C and Siren14?

On 03/15/2013 10:41 AM, Richard Kenner wrote:
> There appears to be a disagreement between the encoding given in the
> sources for Siren14 that are downloaded from Polycom (and the ITU, both
> are the same) and that implemented by codec_siren14.so.  The latter
> agrees with the actual device.
>
> If I make a .sln32 file and run the encoder from ITU/Polycom with
>
> 	encode 0 foo.sln32 foo.siren14 48000 14000
>
> the resulting file doesn't play back correctly with the Digium's
siren14
> codec.  I know the parameters are correct because the file is the same
> size as that made by the Digium codec.
>
> Both sets of decoders/encoders (Digium and Polycom/ITU) are symmetric and
> can decode what they encode, but neither can read the encoding of the
other.
>
> Is there some subtle difference between G.722.1C and Siren14?
>
>
G,722.1C is not the same as Siren 14. This is stated in the Polycom 
material but they don't really indicate how different the two are. More 
importantly, they are vague about whether the two can be expected to 
interwork satisfactorily.

Polycom only offer source code for G.722.1C, so you can't really figure 
out the differences for yourself. People are really sloppy about these 
names and something called siren14 might well be G.722.1C. I assume 
something called G.722.1C is always G.722.1C.

Steve

I'm answering my own email here:
> There appears to be a disagreement between the encoding given in the
> sources for Siren14 that are downloaded from Polycom (and the ITU, both
> are the same) and that implemented by codec_siren14.so.  The latter
> agrees with the actual device.
The disagreement is in byte-swapping of the encoded stream.  Once that's
done, things work fine.  If anybody wants a codec that can transcode
between Siren14 and slin32 (which is better than Digium's codec_siren14
codec which goes to slin and slin16), let me know.  I can send a file that
calls the Polycom/ITU code.