Apple

Video: I know X, what does WebRTC get me?

Posted on by Russell Trafford-Jones

WebRTC is now a W3C standard providing sub-second peer-to-peer video and audio streaming with NAT traversal. Widely used for video conferencing, its sub-second latency has also been the focus of video streaming companies such as Millicast and Limelight (to name but two) who aim to deliver this otherwise peer-to-peer technology to thousands or millions of people in under a second enabling interactive video, gamefied streams, auctions and ultra-low-latency sports.

Addressing directly people using other streaming protocols, Pion creator Sean DuBois spoke at SF Video Tech about what WebRTC brings over and above protocols like RTMP, SRT and RIST. At the heart of it, WebRTC, like SRT and RIST, creates a connection over which it can send a variety of data. Whilst we expect media to be sent, actually, file transfer can be easily achieved – let’s not forget the whole of SRT is build upon UDT which is specifically a file delivery utility. Where file transfer can be achieved, so can real-time data & metadata transfer.

Sean quickly summarises WebRTC as a Protocol between (typically) browsers, an peer-to-peer secure connection over which multiple audio & video streams can flow. In common with RIST and other recent protocols, it’s based on many pre-existing
technologies such as SRTP, DTLS, ICE and SDP to deliver signalling, connection management, encryption and communication.

 

 

The list of improvements over RTMP is very long. They’re spelt out concisely in the video so we will highlight just a few here. Importantly, low-latency is key. RTMP was low-latency for its time, but not by today’s standards. Google’s Stadia can boast 125ms video latency for a keypress, explains Sean. DTLS and SRTP are essential for security but are well understood, trusted methods of securing your data. DTLS is pretty much exactly the same as the TLS which secures your bank transfers, just moved into UDP instead of TCP. However, WebRTC can work by exchanging ‘fingerprints’ (DTLS-SRTP) instead of the full trusted certificate infrastructure that underpins TLS on the web. Removing the requirement for certs is a big boost for flexibility and agility as long as you are confident you can exchange fingerprints securely ahead of time.

NAT traversal is also a big boon where, even with both endpoints behind a firewall, endpoints can always find a way to communicate although this does mean that ICE servers are needed to facilitate connectivity. Within broadcasting, however, it’s more likely that you’ll have control of one end so this is less needed. Sean highlights the ability to send multiple quality levels within the same stream using the ‘simulcast’ ability of WebRTC.

Sean then looks at SRT and RIST. Both of these are low-latency streaming protocols which can, both, also provide sub-second streaming for good connections with a relatively low RTT. Sean highlights the lack of SRT and RIST to negotiate the codec in use and their optional security. Being focused more on delivering contribution feeds, they tend to have a more static configuration often created after a programme of testing to ensure the quality will be acceptable to the broadcaster/streaming provider.

To finish, Sean highlights a whole series of interesting, innovative uses of WebRTC from informal group streaming to drones to shared online games to file transfers and more.

Watch now!
Speaker

Sean DuBois Sean DuBois
Developer, Apple
Creator of Pion WebRTC

Video: LL-HLS Discussion with THEO, Wowza & Fastly

Posted on by Russell Trafford-Jones

Roundtable discussion with Fastly, Theo and Wowza

iOS 14 has finally started to hit devices and with it, LL-HLS is now available in millions of devices. Low-Latency HLS is Apple’s latest evolution of HLS, a streaming protocol which has been widely used for over a decade. Its typical latency has gradually come down from 60 seconds to, between 6 and 15 seconds now. There are still a lot of companies that want to bring that down further and LL-HLS is Apple’s answer to people who want to operate at around 2-4 seconds total latency, which matches or beats traditional broadcast.

LL-HLS was introduced last year and had a rocky reception. It came after a community-driven low-latency scheme called LHLS and after MPEG DASH announced CMAF’s ability to hit the same 2-4 second window. Famously, this original context, as well as the technical questions over the new proposal, were summed up well in Phil Cluff’s blog post which was soon followed by a series of talks trying to make sense of LL-HLS ahead of implementation. This is the Apple video introducing LL-HLS in its first form. And the reactions from AL Shenker from CBS Interactive, Marina Kalkanis from M2A Media and Akamai’s Will Law which also nicely sums up the other two contenders. Apple have now changed some of the spec in response to their own further reasearch and external feedback which was received positively and summed up in, THEO CTO, Pieter-Jan Speelmans’ recent webinar bringing us the updates.

In this panel, Pieter is joined by Chris Buckley from Fastly Inc. and Wowza’s Jamie Sherry discussing pressing LL-HLS into action. Moderator Alison Kolodny hosts the talk which covers a wide variety of points.

“Wide adoption” is seen as the day-1 benefit. If you support LL-HLS then you’ll know you’re able to hit a large number of iPads, iPhones and Macs. Typically Apple sees a high percentage of the userbase upgrade fairly swiftly and easily see more than 75% of devices updated within four months of release. The panel then discusses how implementation has become easier given the change in protocol where the use of HTTP/2’s push technology was dropped which would have made typical CDN techniques like hosting the playlists separately to the media impossible. Overall, CDN implementation has become more practical since with pre-load hints, a CDN can host many, many connections into to it, all waiting for a certain chunk and collapse that down to a single link to the origin.

One aspect of implementation which has improved, we hear from Pieter-Jan, is building effective Adaptive Bit Rate (ABR) switching. With low-latency protocols, you are so close to live that it becomes very hard to download a chunk of video ahead of time and measure the download speed to see if it arrived quicker than realtime. If it did, you’d infer there was spare bit rate. LL-HLS’s use of rendition reports, however, make that a lot easier. Pieter-Jan also points out SSAI is easier with rendition reports.

The rest of the discussion covers device support for LL-HLS, subtitles workflows, the benefits of TLS 1.3 being recommended, and low-latency business cases.

Watch now!
The webinar is free to watch, on demand, in exchange for your email details. The link is emailed to you immediately.
Speaker

Chris Buckley
Senior Sales Engineer,
Fastly Inc.
Pieter-Jan Speelmans Pieter-Jan Speelmans
CTO,
THEO Technologies
Jamie Sherry Jamie Sherry
Senior Product Manager,
Wowza
Alison Kolodny Moderator: Alison Kolodny
Senior Product Manager of Media Services,
Frame.io

Video: The challenges of deploying Apple’s Low Latency HLS In Real Life

Posted on by Russell Trafford-Jones

HLS has taken the world by storm since its first release 10 years ago. Capitalising on the already widely understood and deployed technologise already underpinning websites at the time, it brought with it great scalability and the ability to seamlessly move between different bitrate streams to help deal with varying network performance (and computer performance!). In the beginning, streaming latency wasn’t a big deal, but with multi-million pound sports events being routinely streamed, this has changed and is one of the biggest challenges for streaming media now.

Low-Latency HLS (LL-HLS) is Apple’s way of bringing down latency to be comparable with broadcast television for those live broadcast where immediacy really matters. The release of LL-HLS came as a blow to the community-driven moves to deliver lower latency and, indeed, to adoption of MPEG-DASH’s CMAF. But as more light was shone on the detail, the more questions arose in how this was actually going to work in practice.

Marina Kalkanis from M2A Media explains how they have been working with DAZN and Akamai to get LL-HLS working and what they are learning in this pilot project. Choosing the new segment sizes and how they are delivered is a key first step in ensuring low latency. M2A are testing 320ms sizes which means very frequent requests for playlists and quickly growing playlist files; both are issues which need to be managed.

Marina explains the use of playlist shortening, use of HTTP Push in HTTP2 to reduce latency, integration into the CDN and what the CDN is required to do. Marina finishes by explaining how they are conducting the testing and the status of the project.

Watch now!
Speaker

Marina Kalkanis Marina Kalkanis
CEO,
M2A Media

Video: Introducing Low-Latency HLS

Posted on by Russell Trafford-Jones

HLS has taken the world by storm since its first release 10 years ago. Capitalising on the already widely understood and deployed technologies already underpinning websites at the time, it brought with it great scalability and the ability to seamlessly move between different bitrate streams to help deal with varying network performance (and computer performance!)

HLS has continued to evolve over the years with the new versions being documented as RFC drafts under the IETF. Its biggest problem for today’s market is its latency. As originally specified, you were guaranteed at least 30 seconds latency and many viewers would see a minute. This has improved over the years, but only so far.

Low-Latency HLS (LL-HLS) is Apple’s answer to the latency problem. A way of bringing down latency to be comparable with broadcast television for those live broadcast where immediacy really matters.

Please note: Since this video was recorded, Apple has released a new draft of LL-HLS. As described in this great article from Mux, the update’s changes are

  • “Delivering shorter sub-segments of the video stream (Apple call these parts) more frequently (every 0.3 – 0.5s)
  • Using HTTP/2 PUSH to deliver these smaller parts, pushed in response to a blocking playlist request
  • Blocking playlist requests, eliminating the current speculative manifest request polling behaviour in HLS
  • Smaller, delta rendition playlists, which reduces playlist size, which is important since playlists are requested more frequently
  • Faster rendition switching, enabled by rendition reports, which allows clients to see what is happening in another playlist without requesting it in its entirety”[0]

Read the full article for the details and implications, some of which address some points made in the talk.

Furthermore, THEOplayer have released this talk explaining the changes and discussing implementation.

This talk from Apple’s HLS Technical Lead, Roger Pantos, given at Apple’s WWDC conference this year goes through the problems and the solution, clearly describing LL-HLS. Over the following weeks here on The Broadcast Knowledge we will follow up with some more talks discussing real-world implementations of LL-HLS, but to understand them, we really need to understand the fundamental proposition.

Apple has always been the gatekeeper to HLS and this is one reason the MPEG DASH exists; a streaming standard that is separate to any one corporation and has the benefits of being passed by a standards body (MPEG). So who better to give the initial introduction.

HLS is a chunk-based streaming protocol meaning that the illusion of a perfect stream of data is given by downloading in quick succession many different files and it’s the need to have a pipeline of these files which causes much of the delay, both in creating them and in stacking them up for playback. LL-HLS uses techniques such as reducing chunk length and moving only parts of them in order to drastically reduce this intrinsic latency.

Another requirement of LL-HLS is HTTP/2 which is an advance on HTTP bringing with it benefits such as having multiple requests over a single HTTP connect thereby reducing overheads and request pipelining.

Roger carefully paints the whole picture and shows how this is intended to work. So while the industry is still in the midst of implementing this protocol, take some time to understand it from the source – from Apple.

Watch now!
Download the presentation

Speaker

Roger Pantos Roger Pantos
HLS Technical Lead,
Apple