# Channel choosing unexpected codecs?

**URL:** <https://community.asterisk.org/t/channel-choosing-unexpected-codecs/15673>\
**Category:** Asterisk Support\
**Created:** [July 19, 2007, 12:01am UTC](https://community.asterisk.org/t/channel-choosing-unexpected-codecs/15673 "2007-07-19T00:01:22Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![cstefani](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@cstefani](https://community.asterisk.org/u/cstefani)\
**Post date:** [July 19, 2007, 12:01am UTC](https://community.asterisk.org/t/channel-choosing-unexpected-codecs/15673/1 "2007-07-19T00:01:22Z")

</div>

I’m unsure if what I’m seeing is correct or not in my channel info for a sip cleint making a call in terms of which codecs are being used. I am running Asterisk 1.4.2, I have sip.conf set to force alaw (g.711) on my sip clients.

When I call up using one of those clients and do a 'core show channel x/channel" I see this (excerpt):

NativeFormats: 0x8 (alaw)  
WriteFormat: 0x40 (slin)  
ReadFormat: 0x8 (alaw)  
WriteTranscode: Yes  
ReadTranscode: No  
1st File Descriptor: 16

I’m a little confused because I would think the NativeFormats, WriteFormat and ReadFormat would all be alaw, instead of alaw, slin, alaw.

Is this expected? or do I have a configuration issue? I am battling some other sound quality problems for this system (it’s an inhouse only system, meaning no outside calls) so I’m going through each possible area one step at a time and looking for anomilies.

Thanks,

Colin