I have a Raspberry Pi running raspbx (http://www.raspberry-asterisk.org/) with Asterisk Ver. 11.20.0 / FreePBX 126.96.36.199. Attached is a mobile stick with a SIM card from my cell phone operator.
I am using Zoiper 1.30 for Android als SIP client on my Sony Xperia Z3 Mini runnin Android 5.1.1.
Generally everthing works fine, but the opposite site always has bad audio quality (I don't have bad quality on my site). For the calls I use my WLAN and of course the mobile stick with the SIM card.
I have the same problem with my Samsung Galaxy S2 with Zoiper als SIP client.
If I am using a notebook with Windows 7 and the jitsi sip client (connected via WLAN) or a Cisco hard phone (connected via LAN) the audio quality on the opposite site is fine.
I bought in the meantime the G.729 codec and I am also a Zoiper GOLD member. I tried differnt codec (but not all until now). The quality on the opposite site is different with the different codes, but I did not get a good audio quality on the opposite site.
So my questions are:
- Which codec should I use?
- What else can be done to get a better audio quality for the opposite site?