I've run some audio quality experiments and I'd appreciate some input. These cuts are best listened via headphones. All cuts are encoded at 64Kb/s mono. Audio was fed into phones via headset port.
Here's a reference of the source I used:
I then ran a test on Android via a G.722 (non Linphone) app:( The Linphone G.722 strangely samples at 8KHz so was unusable)
as you can hear, not perfect, but normal bandwidth for G.722
I then ran LinPhone Opus on the same phone:
Many codec artifacts are present, inferior to G.722. I should note that echo canceler was off.
I moved to iPhone and ran a G.722 app
Then to iPhone/LinPhone/Opus
Not artifact heavy, but all low frequencies have been cut. Very tinny sound.
Finally, for reference, I did an encode/decode pass on one of our lab devices that uses Opus (no Linphone)
Summary: Neither mobile implementation of Opus is superior to old fashioned G.722. Other implementations sound *much* better.
We're trying to recommend Linphone mobile for broadcast purposes but with an inferior Opus implementation that's difficult. Any thoughts?