All posts tagged SDP

Back in April 2020 a Citizenlab reported on Zoom’s rather weak encryption and stated that Zoom uses the SILK codec for audio. Sadly, the article did not contain the raw data to validate that and let me look at it further. Thankfully Natalie Silvanovich from Googles Project Zero helped me out using the Frida tracing tool and provided a short dump of some raw SILK frames. Analysis of this inspired me to take a look at how WebRTC handles audio. In terms of perception, audio quality is much more critical for the perceived quality of a call as we tend to notice even small glitches. Mere ten seconds of this audio analysis were enough to set me off on quite an adventure investigating possible improvements to the audio quality provided by WebRTC. ...  Continue reading

webrtcH4cKS: ~ Not a Guide to SDP Munging

SDP has been a frequent topic, both here on webrtcHacks as well as in the discussion about the standard itself. Modifying the SDP in arcane ways is referred to as SDP munging. This post gives an introduction into what SDP munging is, why its done and why it should not be done. This is not a guide to SDP munging.

Want to keep up on our latest posts? Please click here to subscribe to our mailing list if you have not already. We only email post updates. You can also follow us on twitter at @webrtcHacks for blog updates. ...  Continue reading

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. ...  Continue reading

As the year 2017 comes to an end, there was a small present. Hangouts started to support Firefox with WebRTC instead of rejecting access – plugin access had been unavailable since Firefox 53 removed NPAPI in April 2017. While it had been public for a while that the Firefox WebRTC team had been testing this, it was a nice Christmas present to see this shipped. Tsahi Levent-Levi was one of the first people to notice.
This comes at a time where other Google teams are being criticized for promoting Chrome-only experiences. Kudos to the Hangouts team for showing that you still care about the web as an open platform! ...  Continue reading

We have have had many posts on Session Description Protocol (SDP) here at werbrtcHacks. Why? Because it is often the most confusing yet critical aspects of WebRTC. It has also been among the most controversial. Earlier in WebRTC debates over SDP lead the to the development of the parallel ORTC standard which is now largely merging back into the core specifications.  However, the reality is non-SDP based WebRTC is still a small minority of deployments and many have doubts this will change any time soon despite its formal acceptance. ...  Continue reading

WebRTC 1.0 uses SDP for negotiating capabilities between parties.  While there are a growing number of objects coming to WebRTC to avoid this protocol from the 90’s , the reality is SDP will be with us for some time. If you want to do things like change codecs or adjust bandwidth limits, then you’re going to need to “munge” SDP for the time being.

At a recent WebRTC Boston, Nick Gauthier of MeetSpace described how he used SDP modification and other techniques to jam up to 10 video callers into a single conference without a media server. Not everyone has a good reason to do this, but there are certainly plenty of applications where having more precise control of your bandwidth consumption would be useful. You can see his video here or check out his technique and thorough explanation on how to munge SDP to adjust individual bandwidth usage below. ...  Continue reading

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...  Continue reading

For the first time, Chrome, Firefox and Edge can “talk” to each other via WebRTC and ORTC. Check the demo on Microsoft’s testdrive.

tl;dr: don’t worry, audio works. codec interop issue…

Feature Interoperability Notes
ICE yes Edge requires end-of-candidate signaling
DTLS yes
audio yes using G.722, Opus or G.711 codecs
video no standard H.264 is not supported in Edge yet
DataChannels no Edge does not support dataChannels

As a reader of this blog, you probably know what WebRTC is but let me quote this:

WebRTC is a new set of technologies that brings clear crisp voice, sharp high-definition (HD) video and low-delay communication to the web browser.

In order to succeed, a web-based communications platform needs to work across browsers. Thanks to the work and participation of the W3C and IETF communities in developing the platform, Chrome and Firefox can now communicate by using standard technologies such as the Opus and VP8 codecs for audio and video, DTLS-SRTP for encryption, and ICE for networking. ...  Continue reading