Compression Revisited

Compression Revisited

an example of the compression artifact “banding”

If my last post made it seem like I hate compression in all its forms, you’ll have to forgive me. The simple fact is, without compression, there would be no digital video. All video is compressed. Period. Usually at the point of capture, then for exhibition at movie theaters, then again for home video. Even movies or TV shows shot on film are later transferred to digital for post production and compressed. There is no way to have a moving digital image of any kind without some form of compression.

 

For years, most popular digital video formats and capture devices have used H.264 compression. You don’t need to know exactly what H.264 is or how it works. Suffice to say, it’s been with us for a long while now, and it’s time in the spotlight is 

running out. Why? Because we’re moving ever faster towards needing video that maintains H.264’s quality, but with much better efficiency.

 

Enter H.265 (aka HEVC). While the similarity in naming to H.264 suggests there’s not a big difference, H.265 is an entirely different beast and the next frontier in compression.

 

So why are we, or am I, suddenly talking about the AV industry’s most boring topic? Well, because of Game of Thrones naturally. What, did you think I was going to ramble on about a Starbucks cup? No, compression is a big deal now because winter came and for a lot of folks it didn’t come with a very spectacular view! Suddenly the whole world cares about compression, even if HBO and the show’s creators would rather blame it on our lack of calibration. (Don’t get me started.)

 

You see, compression not only allows for digital video to exist in the first place but  also allows for so many of us to enjoy it all at the same time. So when a lot of people all decided they wanted to see some dragon porn at precisely 8 p.m. on the same Sunday night, it took a fair amount of compression to make that happen. Why?

Because digital video files are huge—not to mention complicated. Not like, “Oh, you attached a big file to that last email,” but rather, “Damn, you know I don’t have unlimited data on my cellular plan!” They’re actually even larger than that. In many ways, we’ve long since taken digital video for granted, because prior to the Battle of Winterfell, the only people who really griped about compression were AV nerds like me.

Compression Revisited

For what it’s worth, even most AV nerds misrepresent compression. To give you an idea of what I mean, here’s a comparison between the amount of data it takes to deliver a 4K HDR stream via Netflix (or similar services) compared to the amount of data that UHD Blu-ray discs and your local cineplex deliver.

 

Most nerds will tell you (ignorantly) that the line between unacceptable 

garbage and perfect quality video falls somewhere between the bottom line and the middle one. That argument looks sort of silly, though, when you compare all of the above with truly uncompressed 4K video (see the chart below). The difference between the most and least compressed digital video you as a consumer can access is minuscule by comparison.

Compression Revisited

Again, this isn’t a conversation most people are having. But when everyone’s favorite cousin-f’ing dating show suddenly looks like The Lego Movie, well, people notice.

 

Mind you, as I indicated in my last post, I’m not saying there’s no such thing as too much compression. As we saw with Game of Thrones, you can reach the breaking point of any codec. But it’s not anyone’s fault. You see, we’ve only had digital video in a

meaningful way for a very short time. While digital video has existed since the ‘80s and ‘90s, it didn’t really become the standard until the early 2000s—which means we’ve covered a hell of a lot of technological ground in a very short time.

 

H.264 has been a godsend for digital video both at the capture and exhibition levels. But it does have limitations—not in quality, mind you. Believe it or not, H.264 is robust enough to handle even 8K-resolution files. No, H.264’s limitation is that for as compressed as it is, it actually doesn’t compress enough, so one of two things has to happen. Either you need to compress the files right up to their limit so more people can watch them on demand—thus the GoT debacle—or two, you need a new compression scheme. That’s where H.265 comes into play.

 

H.265 doesn’t really promise to do anything better than its predecessor, except retain the same or better quality but at a quarter of the size. That is all great news. But to get the same horsepower from an engine one quarter the size, you need to do some tweaking—or in this case, some fairly substantial computing.

 

As a result, not everything in today’s modern AV eco system is H.265 equipped, or compatible. Moreover, not every modern camera has H.265 capabilities despite being so-called state of the art.

 

In other words, we find ourselves in a bit of in-between state, a mixed bag of both H.264 and H.265 content and capability. That’s why, at the moment, Netflix can even rival silly spinning discs when it comes to picture quality, whereas other streaming providers, like HBO Go or HBO Now, can end up looking awful while eating up the same amount of your internet data.

 

The good news is that we’re marching ever forward toward the full-scale adoption of H.265—which, in theory, should make something like that disastrous Thrones episode a thing of the past. But until that day comes when we’re all able to get on the same page, more and more of us may have to come to grips with compression and why it is both the lifeblood of digital video and its achilles heel.

Andrew Robinson

Andrew Robinson is a photographer and videographer by trade, working on commercial
and branding projects all over the US. He has served as a managing editor and
freelance journalist in the AV space for nearly 20 years, writing technical articles,
product reviews, and guest speaking on behalf of several notable brands at functions
around the world.

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