Video coding has moved on considerably in the last 14 years and it continues to be increasingly important.

One change is that we all use video a lot more now. We have more screens in our homes, which have higher resolutions and we’re streaming more video. At the same time, processors have become faster and more capable. If you put all of that together then you have more processing power and more demand for high definition video, transmission, storage and streaming. New video codecs such as HEVC/H.265 and VVC/H.266 can compress high resolution video more efficiently, making use of the faster processors that we now have. All of this means that there are plenty of new developments to explain to the reader.

There’s another reason that I wrote this new book. I spend a lot of my time explaining video coding and I am always looking for new ways to explain the core concepts. I’ve rewritten all my explanations of the key ideas of video coding in what I hope is a fresher, more accessible way, with literally hundreds of new examples and diagrams.

In this new book, I explain all the basic concepts of video coding by using lots of diagrams and easy to follow explanations. These explanations will give you a good start, but I think there is no substitute for trying experiments yourself.

My recommendation is to buy the book, take a look, review the explanations and then start thinking, “Right, how do I actually change the quantizer?”, “Just how much better is H.266 compared to H.264 or H.265?” 

You find out the answers to these and other questions by experimenting yourself with video codecs. It may be a little bit of a learning curve, but I can guarantee it's not too steep! You don’t need an engineering or a computing degree to get started, anyone can try it and get their hands dirty. I feel that running your own experiments can give you a more intuitive understanding of what it means to have good compression and what it means to have good quality. This is how you really begin to understand the trade off between compression, video quality and the amount of computation that is required. And then if somebody releases a new codec and claims that it’s the best one yet, you can make your own measurements and reach your own conclusions, instead of just taking their word for it.

There is no easy answer to that question! H.264 has been around for 20 years now, and it's an absolute workhorse. It is probably still the most widely used video codec. However, if you've got faster processors available, or if you are looking at higher definition video like HD and 4K video, then you might expect better performance out of H.265 or even H.266. Of course, the answer is going to depend on factors such as how much computation you have available, the video content you’re working with and the way in which the codec has been implemented in software or hardware.

The best codec very much depends on the situation. There are codecs and formats available that have different features and are flexible in different ways. The best codec will really depend on what you're coding, what you're using to code it, and what you're coding it for.

Is H.265 twice as good as H.264? Is H.266 twice as good as H.265? Is AV1 better or worse than H.265? You'll find publications and articles disagreeing about these questions. Part of the answer is that video codec implementations are not the same. For example, the H.265 standard tells you certain things about a video decoder and it implies certain things about a video encoder. How the actual video encoder is put together is largely up to the designer.

Some codecs are deliberately computationally efficient. This means that they go really fast, but the compression versus quality performance might not be particularly good. Other codecs implementing the same standard might use more sophisticated encoding methods. You might get better compression for the same quality or better quality for the same compression, however it might take a lot more computation.

No two codec implementations are the same and there are so many different factors involved that can make it difficult to reach a single answer about performance.

Absolutely! In the 1990s, people would ask me “What are you working on?”. “Video compression” was my answer. More than once I heard the opinion, “oh, we won't need video compression soon. Bandwidth is increasing so much”. Of course, the exact opposite happened. Bandwidth has increased so much since the 1990s but the demand for high-resolution has increased even more. Think of a typical family household nowadays, where everyone might be watching video at the same time, on a different screen. So we actually need video compression now more than we ever did.

So yes, a colleague did offer me that bet of $100. I didn’t take that bet, but I wish I had!

The answer to that, is determined by the trade-off between computation, video coding performance and backwards compatibility. For example, the majority of video that is coded, streamed over the internet and stored on devices, is still using the 20 year old H.264 format. Therefore, many devices need to support H.264 to make sure they are still compatible with the video that’s out there.

These days, a lot of electronic devices support H.265, however not all devices can handle it. As the processors improve, and as we generate future generations of processors, we might see H.265 become very widely supported and we might expect to see growing support for H.266, and so eventually H.264 may become obsolete - but we are a long way from that point. This means that you might have the ability now to choose a newer codec, if you have a high performance processor and if the decoder can also support the desired codec. As processing power continues to improve, there’s an opportunity to develop and use increasingly sophisticated video codecs that improve compression at the expense of more processing power.

There are also codecs or formats that are not standardised by International Organisation for Standardisation / International Electrotechnical Commission (ISO/IEC) and the International Telecommunication Union Telecommunication Standardisation Sector (ITU-T) such as VP9 and AV1 and then there are other formats which might have more specialist applications. There are lots of reasons why you know you might want to use different codecs in different scenarios, and nobody's yet agreed on a single codec that covers all the backward compatibility.

Until we get a one-size-fits-all codec, I think we are still going to see this wide range of different codecs and formats.