Voice Over IP (VOIP) / Audio sampling combined with ethernet

dorsiareservations · Joined: 16 Nov 2006 Posts: 10

I am starting a project, and was wondering if any one had tried this yet. My final prodect is to make a headset with a PIC in it along with a keypad, and then you can plug the headset into the LAN, and dial an IP of anyone on your network. Sounds cool?

Well, I have never done audio processing before, and the ethernet code with ENC28j60 from CCS is kind of sketchy for me. Should I use a dsPIC, along with an ethernet setup, an 18f J series with an external DAC of some sort, or just use an 18F J series and power through it. I have never used a DAC, or do I know how audio encoding works, especially sending it over UDP. If anyone could help me out with some suggestions/tips, I would be much appreciated.

asmallri · Joined: 12 Aug 2004 Posts: 1635 Location: Perth, Australia

You main challenge will be dealing with the limited amount of ram in a PIC. A dsPIC generally has more RAM available than a PIC18F and is therefore a better candidate than a PIC18F for audio type applications of this nature.

Typically, VoIP packets contain 20ms of sample data per packet. The packet size if a function of the encoding mechanism used (bit rate, mono versus stereo, compression ratio etc).

If you are trying to interface with a "standard client" then this will determine the protocol you will use. If you are developing your own client application for the PC then this is not such a problem.

Voice over IP is transported over UDP as packet loss for voice is preferential to jitter and latency variation introduced by FTP recovery in the event of packet loss in the network.
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dorsiareservations · Joined: 16 Nov 2006 Posts: 10

Interesting. I might be biting off more than I can chew with this, but I am going to give it a shot. I have been wanting to try and use some dsPIC's, but you cant compile them with the CCS compiler. We have been a long time user of CCS, but we are thinking of switching because they dont seem to be keeping up with the pace. Any suggestions on other compilers or if anyone has heard of when an update is going to happen?