The rate of write() in channel driver being called

Hi,

 

I am writing the channel driver of the FXS/FXO ports of our VoIP gateway board.

When talking with a SIP softphone (SJPhone), I found that my write() function will be continuously called five times about every 100 ms.

That is, the interval between these five calls is almost zero. After the five calls, it must wait about 100 ms for next 5 calls.

However, the sample number of each RTP packet is set as 160, i.e. 20 ms per packet.

By capturing the packets sent by SJPhone, we found that it really sends one voice RTP packet every 20 ms.

It seems that Asterisk buffers the incoming voice packets from network and then sends a number of them to the other call leg.

Could you tell me how does Asterisk deal with the incoming packets? And, may we adjust the buffering delay?

Thanks a lot.

 

Sincerely Yours,

--

Guan-Hsiung Liaw (¹ù«a¶¯)

Assistant Professor

Department of Information Engineering

I-Shou University

1, Section 1, Hsueh-Cheng Rd.,

Ta-Hsu Hsiang, Kaohsiung County,

Taiwan 840, R.O.C.

 

Tel: 886-7-6577711 ext. 6529

e-mail: ghliawisu.edu.tw