[Asterisk-Users] Standard Sound Files Distortion

[Tim Panton]

On 28 Jun 2006, at 19:50, Douglas Garstang wrote:

>> -----Original Message-----
>> From: Doug Lytle [mailto:support at drdos.info]
>> Sent: Wednesday, June 28, 2006 12:31 PM
>> To: Asterisk Users Mailing List - Non-Commercial Discussion
>> Subject: Re: [Asterisk-Users] Standard Sound Files Distortion
>>
>>
>> Douglas Garstang wrote:
>>> I've been noticing lately what seems to be some distortian
>> in the standard asterisk sound files, used for voicemail.
>> These files are stored on the local Asterisk system. When
>> Asterisk plays them, I can hear some cracles and pops. I'd
>> never noticed these until recently.
>>>
>>>
>> What I've learned from reading the list, is it usually is a sign of
>> shared IRQs.  Just a thought.
>
> Thanks for the reply. I just worked out what it was. I had ulaw  
> copies of all the sound files in the digits/ directory. For some  
> reason, the ulaw files either had the cracks and pops in the  
> recordings, or when asterisk played the ulaw files, it generated  
> the cracks and pops.

I've noticed something that may (or may not) be related.

If you have a sound file that isn't an exact multiple of 20ms long,
then asterisk 1.2.9.1 (don't know about other versions - yet) sends
out a 'partial' packet with the remaining data in it. For ulaw,
the data would normally be 160 bytes, but a few (the last?) packet(s)
might be 54 bytes (or whatever). This confuses my softphone.
Do we think this is correct behavior ? Shouldn't
asterisk pad the sound out to 20ms?

Note - this never occurs with GSM data, like the
'standard' voice files, as gsm is always a multiple of
20ms long.

T.

Tim Panton
tim at mexuar.com