Guide

webrtcH4cKS: ~ VR Video Calling with WebRTC and WebVR (Dan Jenkins)

Posted by Dan Jenkins on August 27, 2018
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WebRTC isn’t the only cool media API on the Web Platform. The Web Virtual Reality (WebVR) spec was introduced a few years ago to bring support for virtual reality devices in a web browser. It has since been migrated to the newer WebXR Device API Specification.

I was at ClueCon earlier this summer where Dan Jenkins gave a talk showing that it is relatively easy to add a WebRTC video conference streams into a virtual reality environment using WebVR using FreeSWITCH. FreeSWITCH is one of the more popular open source telephony platforms and has had WebRTC for a few years. WebRTC; WebVR; Open Source – obviously this was good webrtcHacks material. ...

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webrtcH4cKS: ~ A playground for Simulcast without an SFU

Posted by Philipp Hancke on July 31, 2018
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You don’t need to fit an SFU opponent when testing simulcast. Image: Hall of Mirrors scene from Bruce Lee’s Enter the Dragon

Simulcast is one of the more interesting aspects of WebRTC for multiparty conferencing. In a nutshell, it means sending three different resolution (spatial scalability) and different frame rates (temporal scalability) at the same time. Oscar Divorra’s post contains the full details.

Usually, one needs a SFU to take advantage of simulcast. But there is a hack to make the effect visible between two browsers — or inside a single page. This is very helpful for single-page tests or fiddling with simulcast features, particular the ability to enable only certain spatial layers or to control the target bitrate of a particular stream. ...

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webrtcH4cKS: ~ Smile, You’re on WebRTC – Using ML Kit for Smile Detection

Posted by Gustavo Garcia on June 11, 2018
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Now that it is getting relatively easy to setup video calls (most of the time), we can move on to doing fun things with the video stream. With new advancements in Machine Learning (ML) and a growing number of API’s and libraries out there, computer vision is also getting  easier to do. Google’s ML Kit is a recent example of a new machine learning based library that makes gives quick access to computer vision outputs.

To show how to use Google’s new ML Kit to detect user smiles on a live WebRTC stream, I would like to welcome back past webrtcHacks author and WebRTC video master  Gustavo Garcia Bernardo of Houseparty. Joining him I would like to also welcome mobile WebRTC expert, Roberto Perez of TokBox.  They give some background on doing facial detection, show some code samples, but more importantly share their learnings for optimum configuration of smile detection inside a Real Time Communications (RTC) app. ...

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webrtcH4cKS: ~ Part 2: Building a AIY Vision Kit Web Server with UV4L

Posted by Chad Hart on March 6, 2018
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In part 1 of this set, I showed how one can use UV4L with the AIY Vision Kit send the camera stream and any of the default annotations to any point on the Web with WebRTC. In this post I will build on this by showing how to send image inference data over a WebRTC dataChannel and render annotations in the browser. To do this we will use a basic Python server,  tweak some of the Vision Kit samples, and leverage the dataChannel features of UV4L.

To fully follow along you will need to have a Vision Kit and should have completed all the instructions in part 1. If you don’t have a Vision Kit, you still may get some value out of seeing how UV4L’s dataChannels can be used for easily sending data from a Raspberry Pi to your browser application. ...

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webrtcH4cKS: ~ AIY Vision Kit Part 1: TensorFlow Computer Vision on a Raspberry Pi Zero

Posted by Chad Hart on March 6, 2018
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A couple years ago I did a TADHack  where I envisioned a cheap, low-powered camera that could run complex computer vision and stream remotely when needed. After considering what it would take to build something like this myself, I waited patiently for this tech to come. Today with Google’s new AIY Vision kit, we are pretty much there.

The AIY Vision Kit is a $45 add-on board that attaches to a Raspberry Pi Zero with a Pi 2 camera. The board includes a Vision Processing Unit (VPU) chip that runs Tensor Flow image processing graphs super efficiently. The kit comes with a bunch of examples out of the box, but to actually see what the camera see’s you need to plug the HDMI into a monitor. That’s not very useful when you want to put your battery powered kit in a remote location. And while it is nice that the rig does not require any Internet connectivity, that misses out on a lot of the fun applications. So, let’s add some WebRTC to the AIY Vision Kit to let it stream over the web. ...

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webrtcH4cKS: ~ Computer Vision on the Web with WebRTC and TensorFlow

Posted by Chad Hart on December 3, 2017
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TensorFlow is one of the most popular Machine Learning frameworks out there – probably THE most popular one. One of the great things about TensorFlow is that many libraries are actively maintained and updated. One of my favorites is the TensorFlow Object Detection API.   The Tensorflow Object Detection API classifies and provides the location of multiple objects in an image. It comes pre-trained on nearly 1000 object classes with a wide variety of pre-trained models that let you trade off speed vs. accuracy. ...

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webrtcH4cKS: ~ How to capture & replay WebRTC video streams with video_replay (Stian Selnes)

Posted by Chad Hart on August 31, 2017
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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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webrtcH4cKS: ~ WebRTC Externals – the cross-browser WebRTC debug extension

Posted by Philipp Hancke on July 28, 2017
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Garden Tools

I am a big fan of Chrome’s webrtc-internals tool. It is one of the most useful debugging tools for WebRTC and when it was added to Chrome back in 2012 it made my life a lot easier. I even wrote a lengthy series of blog post together with Tsahi Levent-Levi describing how to use it to debug issues recently.

Firefox has a similar about:webrtc page which shows the local and remote SDP for each page as well as a very useful grid of ICE candidates. But unlike Chrome it does not show the exact order of API calls or nice graphs obtained from the getStats API. I miss both features dearly. Edge and Safari don’t support similar debugging helpers currently either. ...

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webrtcH4cKS: ~ Reeling in Safari on WebRTC – A Closer Look at What’s Supported

Posted by Chad Hart on June 19, 2017
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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 meant 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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webrtcH4cKS: ~ Am I behind a Symmetric NAT?

Posted by Philipp Hancke on May 15, 2017
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NATs can be a nuisance for VoIP, particularly Symmetric NATs . Fortunately WebRTC includes tools for dealing with them. Image source: http://pinktentacle.com/

WebRTC establishes peer-to-peer connections between web browsers. To do that, it uses a set of techniques known as Interactive Connectivity Establishment or ICE. ICE allows clients behind certain types of routers that perform etwork Address Translation, or NAT, to establish direct connections. (See the WebRTC glossary entry for a good introduction.) One of the first problems is for a client to find what its public IP address is. To do so, the client asks a STUN server for its IP address.

NATs are boxes (physical or virtual) that connect our local private networks to the public internet. They do so by translating the internal IP addresses we use to public ones. They work differently from one another, which ends up requiring WebRTC to rely on both STUN and TURN in order to connect calls. For background on these, check out some of our past posts on this topic like this one and this one. ...

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