Turn your free SIP softphone into a voice quality monitoring instrument with Sevana’s NIQA application

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Hi!

Am 12.05.2010 06:37, schrieb Sevana Oy:
>> Does somebody know how pjsip writes the wavefile? Will it be written
>> exactly like to the audio device (with possible jitter buffer
>> under/overrun and playback-speed adjustments) or will the voice sample
>> be written just one after the other to the wave file?
>
> Call audio will be saved one after another into the same file, however,
> this can also be solved in order to receive recording of a single call.

That's not what I asked - maybe I should make myself more clear:

During a normal phone call, the receiver may do manipulations to the 
audio stream before playing back the audio to the user. For example SIP 
clients often have dynamical jitter buffer - when the buffer gets empty 
the playback speed will be reduced, when the buffer gets full the 
playback speed will be increased, old packets may be ignored completely.

When a call is recorded, this manipulations are not needed because it 
doesn't matter if packets arrive late as for recording there are no 
real-time constraints. The receiver can wait until the RTP packets are 
received and then it saves the audio payload without need for 
manipulation to the wav file.

If a client writes a wav file like described above, and the is no packet 
loss - the recorded file will always be identical to the file sent by 
the other party.

If a client does audio manipulation also for recordings, then the 
recorded file will differ from the original and MOS should be different.

regards
Klaus



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