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All posts by Chad Hart

Decoding video when there is packet loss is not an easy task.  Recent Chrome versions have been plagued by video corruption issues related to a new video jitter buffer introduced in Chrome 58. These issues are hard to debug since they occur only when certain packets are lost. To combat these issues, webrtc.org has a pretty powerful tool to reproduce and analyze them called video_replay. When I saw another video corruption issue filed by Stian Selnes I told him about that tool. With an easy reproduction of the stream, the WebRTC video team at Google made short work of the bug. Unfortunately this process is not too well documented, so we asked Stian to walk us through the process of capturing the necessary data and using the video_replay tool. Stian, who works at Pexip, has been dealing with real-time communication for more than 10 years. He has  experience in large parts of the media stack with a special interest in video codecs and other types of signal processing, network protocols and error resilience.

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Long have WebRTC developers waited for the day Apple would come around to WebRTC. It has not been simple for web developers and Apple due to their policy that requires web browsing functionality to use the WebKit engine along with Safari. This mean no WebRTC in Safari, no Firefox or Chrome WebRTC on iOS, no native WebView with WebRTC or iOS API’s (but plenty of 3rd party ones). Despite community efforts and active development inside the WebKit project, it was not entirely clear when there would be at launch. That changed earlier this month when Apple announced a WebRTC-enabled WebKit based on the Google-backed webrtc.org engine was coming to both High Sierra – the next version of OSX – and iOS 11. Even better, WebRTC is available today as part of the free Safari Technology Preview.

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Media servers, server-side media handling devices, continue to be a popular topic of discussion in WebRTC. One reason for this because they are the most complex elements in a VoIP architecture and that lends itself to differing approaches and misunderstandings. Putting WebRTC media servers in the cloud and reliably scaling them is  even harder. Fortunately there are several community experts with deep expertise in this domain to help. One of those experts who has always been happy to share his learnings is past webrtcHacks guest author Luis López Fernández.

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Way back in 47 (version that is), Chrome started to mandate the use of HTTPS in conjunction with getUserMedia. To use HTTPS you need a SSL/TLS certificate.  Xander Dumaine covered this a bit for us before, but I still see a lot of people out there struggle with it. As it so happens, the certificate for my own personal website is about to expire and I’m not too excited about paying $70/year to renew it. Fortunately, there is a new way to get certificates for free through Let’s Encrypt. Let’s Encrypt is a non-profit certificate authority that formed with the backing of many major industry players like Mozilla, Akamai, Cisco, and many others to simplify and automate the process of setting up encryption for your website. Oh, and its completely free.

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Dealing with multi-party video infrastructure can be pretty daunting. The good news is the technology, products, and standards to enable economical multiparty video in WebRTC has matured quite a bit in the past few years. One of the key underlying technologies enabling some of this change is called simulcast. Simulcast has been an occasional sub-topic here at webrtcHacks in the past and it is time we gave it more dedicated attention.

To do that we asked Oscar Divorra Escoda, Tokbox’s Senior Media Scientist and Media Cloud Engineering Lead to walk us through it. Tokbox was one of the first to market with a SFU and Oscar shares some of his learnings below.

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Conference calling is a multi-billion dollar industry that is mostly powered by expensive, high-powered conferencing servers. Now you can replicate much of this functionality for free with a modern browser using the combination of WebRTC and WebAudio.

Like with video, multi-party audio can utilize a few architectures:

  1. Full mesh – each client sends their audio to every other client; the individual streams are then combined locally before they come out of your speaker
  2. Mixed with a conferencing server acting as a Multipoint Control Unit (MCU) – the MCU combines each stream and sends a single set to each client
  3. Routed with a conferencing server in a Selective Forwarding Unit (SFU) mode – each client sends a single stream to the server where it is replicated and sent to the others

This architecture represents a fourth type: client-mixed type where one of the clients acts like the server. This provides the server-less benefits of mesh conferencing without the excessive bandwidth usage and stream management challenges.

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Session Description Protocol (SDP) is a fundamental, but very unintuitive concept behind how WebRTC works today. Its no wonder that the Anatomy of a WebRTC SDP post and the interactive SDP guide by Quobis CTO, Antón Román has been so popular here on webrtcHacks. With all things WebRTC, things have changed and we were due for an update.

We also had some rendering issues on the interactive guide. After failing to figure out how to fix it, I decided to completely rewrite it. It is still has some issues, so please make your pull requests to fix and update it on our github repo here.

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Two weeks ago Microsoft’s Bernard Aboba (and former webrtcHack’s interviewee) gave an update on Edge’s ORTC and WebRTC at the Microsoft Build conference. He covered some big topics including VP8 and WebRTC 1.0 support. You can see the update video at the link above or read the follow-up post for details. Then last week Microsoft announced plug-in free Skype on the Edge browser.

I had some questions; Fippo had some questions; so we asked Bernard if he could publicly respond here. It turned out Bernard and his teammate on the Edge Browser team, Shijun Sun, were building a running list of questions they wanted to address too. Here it is.

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Losing customers because of issues with your network service is a bad thing. Sure you can gather data and try to prevent, but isn’t it better to prevent issues in the first place? What are the most common pitfalls to look out for? What’s a good benchmark? What WebRTC-specific user experience elements should you spend your limited resources focusing on? No service can be perfect, so what is a reasonable error rate? These are all tough questions to answers without decent industry data.

Fortunately Lasse Lumiaho and Varun Singh from callstats.io have agreed to share some stats from their WebRTC monitoring service to help you answer these questions.  Their service does not monitor every WebRTC service,  but their 100+ customer base does provide a statistically meaningful sample to help give you some practical metrics for planning and comparison.

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Back in October 2013,  the relative early days of WebRTC, I set out to get a better understanding of the getUserMedia API and camera constraints in one of my first and most popular posts. I discovered that working with getUserMedia constraints was not all that straight forward. A year later I gave an update after the situation with Chrome was greatly improved, but Firefox at the time effectively only supported a single resolution so constraints were not much help. Specifically, I am interested in understanding what happens when you ask for a specific resolution. You might want to have a specific resolution returned by getUserMedia if you want to match the camera resolution to a specific video area to have a 1 to 1 pixel correlation, in a computer vision application where each pixel represents a distance, or if you are dealing with non-standard video devices.

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