Please find below Chrome 39 WebRTC Release notes:-
Issue 1746 :- Added support for getting STUN candidates from the TURN server.
Issue 1906 :- Added support for sdp parameter maxplaybackrate for Opus. You can test this parameter in apprtc demo by passing url parameter 'opusmaxpbr'.
Issue 3570 :- Added support to handle TURN allocation mismatch error code 437 in accordance with RFC 5766.
Issue 3712 :- With VP8 codec, the encoder has to sometimes drop frames to maintain the bit-rate. A lot of frame-drops can look worse than scaling image down. Now we added ability to scale down frames before encoding to improve quality.
Added functionality in AGC to raise the microphone level if needed at startup. This is based on some user reports of not being able to hear others in a call.The effect on the AGC is that it can not raise the volume, since it is either not audible or too low and therefore treated as background noise. Now we force the level up to ~10% at startup if it is below that.
Issue 3559 :- Fixed issue with SCTP packets being received out of order.
Issue 3761 :- Fixed Divide-by-zero problem in NetEq's Normal::Process. This was causing a crash in Chrome.
Issue 3785 :- Fixed one way audio issue in Chrome. The problem was that NetEQ was unable to handle a big jump in timestamp.
Issue 3833 :- Fixed problem, now the media content will be send-only if offerToReceive parameter is false and local streams exist.
Issue 3778 :- Fixed problem in SCTP data channel, closing a data channel was causing next open data channel to fail silently.
Issue 423696 :- Fixed audio glitches on Mac when webrtc and webaudio streams are used at the same time.
Issue 424149 :- Fixed problem with Chrome reporting as 0 audio energy for input stream when microphone volume was low.
Issue 420866 :- Fixed Black video problem for Chrome on Android on some Samsung devices.
Issue 414211 :- Fixed problem on Mac, we were not sending DTLS close alert on closing peer connection. It was not happening for NSS but for boringSSL on mac. In Chrome 39 we switched to BoringSSL instead of NSS.
Issue 417245 :- Fixed problem, not all tracks were getting removed before onRemoveStream was called in a multi-track scenario.
Issue 374104 :- Fixed A/V sync issue when FEC was enabled.
Issue 403618 :- Now we close all peer-connections upon OS suspend.