in general, cm12+ roms on the S3 suffer from low speaker/mic volume. try search for "SL-Sound_L5.0.x.zip" on the forums and flash it normally.I've been on Temasek ROM since CM12.1 and everything was fine, but I got stuck on cm12.1 temasek v15.8 for quite a while and out of the blue my mic sound on the default call app was just gone. It worked fine on Messenger though. But since I'm more of a text guy I ignored it for a while. But recently I got a bootloop on it updating facebook (why I even use that tbh) and I decided to update the ROM since it would probably solve that problem.
So today I installed this latest version, followed the installation guidelines for the exception of TWRP (using PhilzTouch something) and everything is fine but the problem with the mic persists. Inexistent in default call app and now is kinda low on messenger (but on hands free is fine). So I haven't got the slightest idea what to do to change this. Any idea what can be done here?
it's basically editing the m0 file, which changes mic/speaker volume. or you could install a custom kernel and edit those values.