Integrating any codec within an android VOIP application

Question

I am working on an android voip application that need not work on PSTN. I am completely novice to this field and any little help will be appreciated.

I started by researching how whatsapp voice call works and found out that it is using PJSIP which is open source sip stack library(Source: What's up with WhatsApp and WebRTC? - webrtcHacks). I also found that codecs are used in voip to compress and then decompress the voip packets.

Knowing that I am extremely comfused betweet those sip libraries and codec. Do an android voip app have to have implement sip library? Every sip library supports a few codec.

Is there any general format by which I can integrate any codec within my android app whether it is OPUS or Speex or anything like that which is independent of sip implementation?

May be I am sounding too confusing but that is true. Even googling so much on this specific topic did not help me and my last stop is this community. Any little guidance will be appreciated.

Answer 1

Yes, usually every app implements the codecs on their own. Some codec is available in the Android SDK but even in these cases a proper implementation is better.

G.711 (PCMU and PCMA) are very simple which can be implemented within a single java class (or even in a single function if you wish). The others are more complicated, but you can find open source implementations for almost each of them.

Also note that codec's are implemented also within PJSIP, so if you are using this library then you already have the most popular codec's available.