[cisco-voip] Creating PCM samples??

[Ryan Ratliff]

These are the specs:

•Raw PCM (no header)

•8000 samples per second

•8 bits per sample

•ulaw compression

•Maximum ring size—16080 samples

•Minimum ring size—240 samples

•Number of samples in the ring evenly divisible by 240

•Ring starts and ends at the zero crossing.

So if you've got 8000 samples per second and your total number of  
samples needs to be evenly divisible by 240 then to keep the math  
simple make the total length of the ringer some increment of 1.5  
seconds.   Of course the max ring size allows for a 2.01 second ring  
file at 16080 samples.

As for the zero crossing I have no idea what that means.  Maybe just  
that the beginning and end of the audio has 0 amplitude (ie silent)?

HTH,

-Ryan

On May 26, 2006, at 12:11 PM, Tim Reimers wrote:



Anyone got any clue on how to set the zero crossings and the number  
of samples to be divisible by 240??

CCMstuff. org and Cisco say to do that..

I've created a steelpan ringer, and the phone plays it, but it's all  
distorted--

Sounds as if I've violated one of the rules regarding the PCM file.
I followed the instructions of 8k samples, 8 bit..pcm ulaw format…
I guess it's the number of samples or something, or not divisible by  
240…

I have no idea how to do that last in Audacity or in Sound Recorder...

Not sure what to do from here….


Thanks, Tim

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