Video: Making Live Streaming More ‘Live’ with LL-CMAF

Squeezing streaming latency down to just a few seconds is possible with CMAF. Bitmovin guides us through what’s possible now and what’s yet to come.

CMAF represents an evolution of the tried and tested technologies HLS and DASH. With massive scalability and built upon the well-worn tenants of HTTP, Netflix and a whole industry was born and is thriving on these still-evolving technologies. But the push to reduce latency further and further has resulted in CMAF which can be used to deliver streams with five to ten times lower latencies.

Paul MacDougall is a Solutions Architect with Bitmovin so is well placed to explain the application of CMAF. Starting with a look at what we mean by low latency, he shows that it’s still quite possible to find HLS latencies of up to a minute but more common latencies now are closer to 30 seconds. But 5 seconds is the golden latency which matches many broadcast mechanisms including digital terrestrial, so it’s no surprise that this is where low latency CMAF is aimed.

CMAF itself is simply a format which unites HLS and DASH under one standard. It doesn’t, in and of itself, mean your stream will be low latency. In fact, CMAF was born out of MPEG’s MP4 standard – officially called ISO BMFF . But you can use CMAF in a low-latency mode which is what this talk focusses on.

Paul looks at what makes up the latency of a typical feed discussing encoding times, playback latency and the other key places. With this groundwork laid, it’s time to look at the way CMAF is chunked and formatted showing that the smaller chunk sizes allow the encoder and player to be more flexible reducing several types of latency down to only a few seconds.

In order to take full advantage of CMAF, the play needs to understand CMAF and Paul explains these adaptations before moving on to the limitations and challenges of using CMAF today. One important change, for instance, is that chunked streaming players (i.e. HLS) have always timed the download of each chunk to get a feel for whether bandwidth was plentiful (download was quicker than time taken to play the chunk) or bandwidth was constrained (the chunk arrived slower than real-time). Based on this, the player could choose to increase or decrease the bandwidth of the stream it was accessing which, in HLS, means requesting a chunk from a different playlist. Due to the improvements in downloading smaller chunks and using real-time transfer techniques such as HTTP/1.1 Chunked Transfer the chunks are all arriving at the download speed. This makes it very hard to make ABR work for LL-CMAF, though there are approaches being tested and trialed not mentioned in the talk.

Watch now!


Paul MacDougall Paul MacDougall
Solutions Architect,

Video: A Survey Of Per-Title Encoding Technologies

Optimising encoding by per-title encoding is very common nowadays, though per-scene is slowly pushing it aside. But with so many companies offering per-title encoding, how do we determine which way to turn?

Jan Ozer experimented with them, so we didn’t have to. Jan starts by explaining the principles of per-title encoding and giving an overview of the market. He then explains some of the ways in which it works including the importance of changing resolution as much as changing

As well as discussing the results, with Bitmovin being the winner, Jan explains ‘Capped CRF’ – how it works, how it differs from CBR & VBR and why it’s good.

Finally, we are left with some questions to ask when searching for our own per-title technology to solve the problem we have such as “can it adjust rung resolutions?”, “Can you apply traditional data rate controls?” amongst others.

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Jan Ozer Jan Ozer
Streaming Learning Center

Video: AV1/VVC Update

AV1 and VVC are both new codecs on the scene. Codecs touch our lives every day both at work and at home. They are the only way that anyone receives audio and video online and television. So all together they’re pretty important and finding better ones generates a lot of opinion.

So what are AV1 and VVC? VVC is one of the newest codecs on the block and is undergoing standardisation in MPEG. VVC builds on the technologies standardised by HEVC but adds many new coding tools. The standard is likely to enter draft phase before the end of 2019 resulting in it being officially standardised around a year later. For more info on VVC, check out Bitmovin’s VVC intro from Demuxed

AV1 is a new but increasingly known codec, famous for being royalty free and backed by Netflix, Apple and many other big hyper scale players. There have been reports that though there is no royalty levied on it, patent holders have still approached big manufacturers to discuss financial reimbursement so its ‘free’ status is a matter of debate. Whilst there is a patent defence programme, it is not known if it’s sufficient to insulate larger players. Much further on than VVC, AV1 has already had a code freeze and companies such as Bitmovin have been working hard to reduce the encode times – widely known to be very long – and create live services.

Here, Christian Feldmann from Bitmovin gives us the latest status on AV1 and VVC. Christian discusses AV1’s tools before discussing VVC’s tools pointing out the similarities that exist. Whilst AV1 is being supported in well known browsers, VVC is at the beginning.

There’s a look at the licensing status of each codec before a look at EVC – which stands for Essential Video Coding. This has a royalty free baseline profile so is of interest to many. Christian shares results from a Technicolor experiment.


Christian Feldmann Christian Feldmann
Codec Engineer,

Video: Scalable Video Coding in HEVC & AV1

While it has never played a big role in practical applications, scalable video coding has been around since the times of MPEG 2, and might actually have some advantages over the multi-rate transmission often applied today. The purpose of scalable coding is to efficiently compress multiple different versions of the same video in one “scalable” bitstream. Actually this sounds like the perfect solution for VOD and streaming applications, but unfortunately it has some downsides and few vendors ever used it. In this talk, Chrstian will review the basic idea of scalable coding, how it is enabled in modern coding standards and the pros and cons of implementing the technology in streaming applications.


Christian Feldmann Chrisitan Feldmann
Codec Engineer,