What is HEVC? Explain high efficiency video coding, H.265 and 4K compression
High efficiency video coding (HEVC), also known as H.265, can achieve twice the compression by Blu-ray optimal video compression. But how it works, is it enough to see more than 4K content?
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I want to call it H.265 because it sounds cool, but its full name is high efficiency video coding (HEVC). It is a new heir of advanced video coding (AVC), also known as H.264, one of the compressed schemes used in Blu-ray.
The HEVC idea is to provide the same level of image quality as the AVC, but with better compression, therefore need to handle less data. If we want 4K / ultra HD broadcast (including satellite), 4K blue light, etc., this is the key.
But is this enough, in this way, how does it work?
Compressed (good, bad and damaged)
Professional HD cameras on the back of the camera is very large. There is no way to easily transport it to your home. Instead, the video is compressed to reduce the amount of data into a form that is easier to manage.
There are many ways to do this, the simplest method is to reduce quality. In some cases, this doesn't matter. Think about you average YouTube video. Not very good, right? This is usually because the video is highly compressed (before or during upload). The heavy pressure may make the resolution remain unchanged, but the image looks more soft, even more noisy, or will produce strange dispersion attention (as shown on the right).
But if the focus is to keep the director's intent, or show off your new 77-inch OLED, this is not a good idea.
So another choice is to use better compression. In this case, you can basically consider "better" as a "smarter" compression. So it uses the same original (video) and find a better way to reduce the amount of data without sacrificing the quality. Every few years, the handling capacity of the gear will increase to a more processor-intensive compression algorithm, and further compress the data without making the image worse.
This difference between "more" compression and "better" compression is important. In fact, these terms are incompupied in this case. You can reduce the amount of data required to reduce the signal by starting compression and making images ugly ("more" compression) or use more efficient compression techniques ("better" compression) to reduce the amount of data required.
Let me say this. Say you have a frame of apples. You need to install 100 apples inside. You can do this with more compression (reducing apples to sauce) or better compression (find a better way to make them suitable, but keep their apples) to do this.
More compression: Apple sauce is better compressed: more apples, the same space
From this delicious example, "more" is easy to compress (smush), and "better" compression requires more thinking and / or better techniques.
Enter H.265
Like HD, data is dense, 4K is worse. Although most of us is accustomed to using H.264 with the advantages of H.264 relative to MPEG-2, the sports image expert group and the International Telecom Alliance's telecommunications standardization department (ITU-T) have begun to study the next generation of video compression, Focus on the future.
Do not want to make small, progressive improvements, every time you introduce new compression criteria, it must be a considerable change. For each jump, the general rule is half the bit rate of the same mass (or has a higher quality at the same bit rate).
How did it do? Mainly by extending AVC (and previous other compression techniques) work mode.
First, it will view multiple frames to see content that does not change. In most scenes of TV programs or movies, most pictures have not changed much. Think about someone talking. The lens is mainly their head. For many frames, the background will not change much. In this regard, most pixels representing their face may not have much change (of course, except their lips). Therefore, it is not to encode each pixel in each frame, but the initial frame is encoded, and then only it is encoded (substantially).
Then, HEVC expands the size of the area viewed for these changes. Basically larger and smaller "blocks" provide additional efficiency. When is a foul, do you have seen blocks in your image? The HEVC can be larger, smaller and larger than the previous compression method. For example, a larger block is found more efficient.
The left is the macroblock processing made by AVC / H.264. As you can see on the right, the HEVC / H.265 encoder has greater flexibility, not to say greater size.
Then other things have been improved, such as motion compensation, space prediction, etc. All of these things can be done through AVC or even earlier, but it needs more cost-effective to process more economically.
In the development phase, the compression algorithm objectively tests its original quantity efficiency, but it also subjectively compares different compression methods and quantities by video professionals in "blind" test, where they don't know which method is. People's factors are essential. Just because the computer said that the first-level compression is better than the other level, it does not mean that it looks better than the other.
Since H.265 has much higher degree of denseness, do not expect to decode your device via a simple firmware upgrade. In fact, this is part of the problem. You need a hardware decoder. If your new media streaming media, cable TV box or BD player has it, then you will set all (assuming you also have HDMI 2.0, so you can get 2160P / 60, not just 2160p / 30). Can high-end PC decodes them through software? maybe. XBOX One or PS4? not necessarily. Everyone likes their favorite console, but remember that the hardware of this generation is equivalent to a normal PC.
Is it enough?
Well, technology is, but there is a big warning. As previously AVCs (and other compression standards), H.265 can be adjusted according to the required bandwidth. Want 4K mediocre internet connection? No problem; turn "dial" (remember appler?). Do you want the best quality? No problem; turn the dial from another direction.
Although this arrangement provides flexibility, it also means "4k" and "UHD" do not necessarily guarantee better image quality than the current "1080P" or "HD". In many ways, high-compressed 4K signals may be worse than the HD signal having a lower compression.
In other words, according to the degree of compression used, stream 4K may look poor than the current 1080P blue light. As Netflix is now transmitted at 15.6 Mbps, the initial signs indicate that 1080p blue looks "cleaner", which confirms some experts' forecasts. possible reason? 1080p Blu-ray is more bandwidth for video than in line stream media, not just the old compression scheme of the disc.
Although all devices have followed the law, the Internet bandwidth is not. Of course, there are some real high-speed connections, but many people are difficult to get a decent HD signal. With Net NeutRality in the United States, the general and cheap 4K streaming media is still cloudy.
Another benefit
Although most of the potential advantages of HEVC are concentrated on 4k, the better compression effect has also brought advantage to HD. The lower the high-definition bandwidth means more people can get HD. A crowd that is too slow to connect to the current HD may be able to obtain HD encoded by HEVC. If you pay by megabytes (mobile or home), lower bit rate means cheaper HD viewing.
end
Start looking for HEVC (or H.265) as a product line for future TV, Blu-ray player and other media players. Almost all major brands of 2014 4K TV contains the necessary hardware decoders, although the 4K TV in 2013 is not. There are more streamers such as Sony FMP-X10 including the necessary hardware.
There are many complaints during the transition of the Blu-ray, and now it has become a reality. In the end, HEVC is also true. Reduce data rate while maintaining quality, is a good thing for everyone.
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