Wednesday, September 28, 2005

A little more VoIP

Well I've done a bit of fiddling with my Asterisk setup. For those that haven't been following this saga: Asterisk server (2GHz Sempron, 512M RAM and 30G drive), a Grandstream BT100 IP Phone and a Sipura SPA-3000. I've finally fix the BT100 registration problem (needed host=dynamic & insecure=yes). I can also use the canreinvite=yes to get the BT100 to talk directly to the SPA-3000 after the call setup starts (the actual RTP portion of the call). This is important if you don't want to hear all sorts of oddities on the phone (clicks, drop outs, really bad echo). Unfortunately the SPA Line 1 and PSTN interfaces don't want to talk to each other directly (all the RTP goes through the Asterisk server, not good). The last problem is the volume level of the call. I set the SPA To PSTN Gain: -3 and the PSTN To SPA Gain: 3. This seems to boost the volume a little and avoids excessive echo that I've seen when I had the gains set to -6 & 0 respectively.

Here's my opinion of the BT100, it's an acceptable phone for experimenting with but I don't think I'll buy another. This phone will have a low SAF (Spouse Acceptance Factor). The buttons are large but feel a little cheap. The overall look is fine, but it would be nice if it had a little more weight so it didn't move around on the desk. I have to say it's features are not bad for the cost. Also Grandstream seems to be constantly updating the code with fixes and improvements. One major problem is the speaker phone. Listening to the speaker phone is difficult because it looses so much volume (even turned all the way up) and the micro phone won't properly pick up my voice at a distance of 2 ft (1 foot away and 1.5 feet below my head) on my desk. Since this phone is well out of warranty I may do some hardware hacking to boot the volume to the speaker and see if I can't improve the mic pickup. I'll have to be careful of feedback. BTW, the handset works fine, though I often have to lower the volume after using the speaker phone. For my next IP phone I'll take a look at the GXP-2000 and other IP phones.

One last thing, I've also been fiddling with the 'ring tones' for the BT100 (I expect that the GXP-2000 has a similar format for it's ring tones). I've been able to listen to the ring tone files from the BT100. I converted them from the G.711 format to wav using sox. The ring2.bin and ring3.bin files are just noise. The ring1.bin is a series of numbers and the final statement of ' You have a call from' nnn-nnn-nnnn, so I think I'm on the correct track. To listen to a ring tone run the command below and then run play ring1.wav:

sox -Ub -r 8000 -t .raw ring1.bin -t .wav ring1.wav

To convert a wav file to a ring tone run this command:

sox -t .wav ring1.wav -Ub -r 8000 -t .raw ring1.bin

Then you copy the ring1.bin to the tftp directory. Unfortunately I've not been able to copy the file to phone a second time (yes it worked previously).


At 10/09/2005 10:23 PM, Anonymous Anonymous said...

Thanks. You saved me a couple bucks/headaches. I was looking @ the same phone for my soon to be Asterisk setup.
bhickman [at} mfire(dot)com


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