Lip-sync Issues: When a Chrome Update Fixes your Application

This post was co-authored by Gustavo Garcia Bernardo, Philipp Hancke and Charley Robinson.

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When WebRTC stuff is really broken, it gets fixed very quickly.

Early in December 2015, shortly after the release of Chrome 47 to the general public, we started to notice a subtle and strange behavior in the Audio/Video of streams during our many daily meetings using WebRTC: the video occasionally wouldn’t stay caught up with the corresponding audio. As with many bugs noticed internally by developers, it took a while for any of us to believe that what we were seeing was a real issue. We call this the inverse of productive dogfooding: rather than assume we are just like our users, we can just as easily decide we are nothing like them.

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How to get a WebRTC Diagnostic Recording from Chrome 49+

WebRTC logoHave you ever had to support a WebRTC application and needed to get packet dumps from the user? Wireshark is a great tool for this, but asking a user to install it and make a dump rarely works. It’s just too complicated. So I was pretty excited when I read the Chrome 49 release notes which described (not in much detail) a new feature called the ‘RTC event log’. This is described as follows:

We now provide a new debug option in chrome://webrtc-internals for tracing internal details (e.g., BWE, jitter buffer state) for audio and video sessions. This option creates a log containing the timing and headers of packets as well as the timing of various internal events. We hope this will help resolve issues related to media transport and jitter buffers; attaching this log when reporting such issues will help us tremendously.

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When a Chrome update breaks your WebRTC application

chrome logoEarly December saw the roll-out of Chrome 47. When doing anything with WebRTC, this is always an interesting time. A release brings new features or may break things, like removing the getUserMedia functionality for insecure origins.

Our metrics clearly track such roll outs as seen below:

# of OpenTok calls

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