[asterisk-users] LAN IAX2 trunk bad audio quality vs. LAN SIP trunk good audio quality

[Gareth Blades]

There should be no noticeable difference between slin, ulaw and alaw so 
what you have is fine. The problem must be elsewhere.

Vieri wrote:
> --- On Thu, 5/13/10, Gareth Blades <list-asterisk at skycomuk.com> wrote:
> 
>> Show the details on the active
>> channels when using both methods and 
>> check what codecs are being used.
> 
> The audio codecs are different:
> 
>            Type: SIP
>           State: Up (6)
>           Rings: 0
>   NativeFormats: 0x4 (ulaw)
>     WriteFormat: 0x40 (slin)
>      ReadFormat: 0x40 (slin)
>  WriteTranscode: Yes
>   ReadTranscode: Yes
> 
>            Type: IAX2
>           State: Up (6)
>           Rings: 0
>   NativeFormats: 0x8 (alaw)
>     WriteFormat: 0x8 (alaw)
>      ReadFormat: 0x8 (alaw)
>  WriteTranscode: No
>   ReadTranscode: No
> 
> By the way, I have this in iax.conf:
> 
> [interboxIAX2]
> deny=all
> allow=ulaw
> allow=gsm
> type=friend
> host=192.168.250.111
> secret=mysecret
> auth=plaintext
> requirecalltoken=no
> qualify=yes
> context=mycontext
> trunk=yes
> username=interbox
> 
> Shouldn't the channel details report ulaw instead of alaw?
> 
> Also, if I change [interboxIAX2] and replace ulaw with alaw, the result is the same (I still experience bad audio quality).
> 
> Maybe I should try slin but how do I "force it"?
> 
>> Vieri wrote:
>>> Hi,
>>>
>>> I have an audio quality problem regarding IAX2. I have
>> 2 Asterisk servers interconnected via 2 LAN trunks at 1Gbps
>> (no nat, no firewall).
>>> One trunk is SIP and the other IAX2.
>>> Normally, I use IAX2 but have noticed easily
>> reproducible audio quality problems (voice in/out is OK but
>> there's a "third" noise overlapping with a "scratchy sound"
>> as if it were some kind of interference).
>>> So lately I setup calls to go through the SIP trunk
>> and audio quality is OK (no "third overlapping noise").
>>> This is happening between Asterisk 1.4.31 and a
>> 1.2.40.
>>> I'm wondering if there's something I can tweak in IAX2
>> to eliminate this artifact.
>>> Could the IAX2 jitter buffer between 1.2 and 1.4 be an
>> issue (I believe it's enabled by default)?
>>> Thanks,
>>>
>>> Vieri
>>>
>>>
>>>
>>>        
>>>
>>
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> 
> 
>       
>