#WebRTC Video Quality Assessment

How to make sure the quality of a [webrtc] video call, or video streaming is good? One can take all possible metrics from the statistic API, is still be nowhere closer to the answer. The reasons are simple. First most of the statistic reported are about network, and not about video quality. Then, it is known, and people who have try also know, that while those influence the perceived quality of the call, they do not correlate directly, which means you cannot guess or compute the video quality based on those metrics. Finally, the quality of a call is a very subjective matter, and those are difficult for computers to compute directly. 

In a controlled environment, e.g. in the lab, or while doing unit testing, people can use reference metrics for video quality assessment, i.e. you tag a frame with an ID on sender side, you capture the frames on the receiving side, match the ID (to compensate for jitter, delay or other network induced problems) and you measure some kind of difference between the two images. Google hasfull stack teststhat do just that for many variations of codecs and network impairments, to be run as part of their unit tests suite.

But how to do it in production and in real-time?

For most of the WebRTC PaaS use cases (Use Case A), the reference frame is not available (it would be illegal for the service provider to access the customer content in any way). Granted, the user of the service could record the stream on the sender side and on the receiving side, and compute a Quality Score offline. However, this would not allow to act on or react to sudden drops in quality. It would only help for post-mortem analysis. How to do it in such a way that quality drops can be detected and act on in real-time without extra recording, upload, download, ….?

Which webrtc PaaS provides the best Video Quality in my case, or in some specific case? For most, this is a question that can’t be answered. How can I achieve this 4×4 comparison, or this zoom versus webrtc, in real time, automatically, while instrumenting the network?

CoSMo R&D came up with a new AI-based Video Assessment Tool to achieve such a feat in conjunction with its KITE testing engine, and corresponding Network Instrumentation Module. The rest of this blog post is unusually sciency so reader beware. 

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H.264 finally a first class citizen in #WebRTC stacks.

VP8 and H.264 codecs are mandatory to implement to be webrtc compliant. Simulcast is a way to use multiple encoders at a time to provide different resolutions of the same media to chose from as a way to adapt to bandwidth fluctuations (and other good things). Unfortunately, while some patches were proposed some two years ago by some including HighFive, libwebrtc did not implement support for simulcast with the H.264 codec. H.264 was then a de-facto secondary codec, and Safari which only supported H.264, could not achieve the same level of adaptation (or quality) than VP8 and some other browsers could. This blog gives more details about the epic journey to get that done, the design of the implementation, and the impact for WebRTC products.

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CoSMo New Offices ! Bringing #Webrtc further, faster.

We had started the cosmo adventure in a co-working space. It was great: we were surrounded by entrepreneur-minded people, supported by great staff (kudos Claire and Evelyn), the space was nice, the roof top incredible, and it accommodated our growth from 1 to 13 local employees in 2017. If you’re looking for a centrally located co-working space in Singapore, I could not recommend any place more than WOTSO co-working space at 19 Cecil Street. The hard truth was that we had outgrown our co-working space.

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