"Last August, Ericsson launched the first h.265 codec, and just six months later, ITU officially approved the hevc / h.265 standard. The full name of the standard is high efficiency video coding, which is quite improved compared with the current H.264 standard. H. 265 aims to transmit higher quality network video under limited bandwidth. It only needs half of the original bandwidth to play video of the same quality. This also means that our mobile devices (mobile phones, tablets) will be able to directly play full HD (1080p) video online. The h.265 standard also supports 4K (4096 & times; 2160) and 8K (8192 & times; 4320) ultra high definition video. It can be said that the h.265 Standard enables network video to keep up with the "high-resolution" of the display screen. You may see that devices supporting h.265 decoding are on the market (such as smart phones, graphics cards, etc.) in a few months. H. H.264 has dominated the past five years, and in the next five or even ten years, h.265 is likely to become the mainstream.
Why is h.265 better than H.264
Before discussing the improvements and advantages of h.265, let's take a look at H.264.
H. 264, also known as MPEG-4 AVC (advanced video coding), is not only a video compression standard, but also a widely used format for recording, compressing and publishing high-precision video. H. H.264 is famous for being a codec standard of Blu ray disc. All Blu ray players must be able to decode H.264. More importantly, because Apple resolutely abandoned Adobe's VP6 coding and chose H.264, this standard has entered thousands of households with hundreds of millions of iPads and iPhones, becoming the absolute overlord in the field of video coding, accounting for more than 80%. H. 264 is also widely used in network streaming media data, various high-definition television terrestrial broadcasting, satellite television broadcasting and other fields.
? H. Compared with the previous coding standards, H.264 has some new features, such as multi reference frame motion compensation, variable block size motion compensation, intra prediction coding, etc. by using these new features, H.264 has higher video quality and lower bit rate than other coding standards, so it has been recognized by people.
H. The coding architecture of 265 / hevc is roughly similar to that of h.264/avc, and mainly includes modules such as intra prediction, inter prediction, transform, quantization, deblocking filter, entropy coding, etc. However, in the hevc coding architecture, the whole is divided into three basic units: coding unit (Cu), prediction unit (PU) and transform unit (TU).
Compared with h.264/avc, h.265/hevc provides more different tools to reduce the bit rate. In terms of coding unit, the size of each macroblock (MB) in H.264 is a fixed 16x16 pixels, and the coding unit of h.265 can be selected from the smallest 8x8 to the largest 64x64. Taking the following figure as an example, the areas with less information (such as the red part of the car body and the gray part of the ground) have larger macroblocks and fewer coded words, while the areas with more details (tires) have smaller and more macroblocks and more coded words, which is equivalent to the focused coding of the image, Thus, the overall bit rate is reduced and the coding efficiency is improved accordingly. Meanwhile, the intra prediction mode of h.265 supports 33 directions (H.264 only supports 8), and provides better motion compensation processing and vector prediction methods.
Repeated quality comparison tests have shown that under the same image quality, the video size encoded by h.265 will be reduced by about 39-44% compared with H.264. Due to different determination methods of quality control, this data will change accordingly. The data obtained from subjective visual test shows that when the bit rate is reduced by 51-74%, the quality of h.265 encoded video can be similar to or even better than h.264 encoded video, which is essentially better than the expected signal-to-noise ratio (PSNR). The evaluation criteria of these subjective visual tests cover many disciplines, including psychology and human visual characteristics. The video samples are very wide. Although they can not be used as the final conclusion, this is also a very encouraging result.
H. Compared with the subjective visual test of H.264 and h.265 encoded video, we can see that the bit rate of the latter is greatly reduced
The current hevc standard has three modes: main, main 10 and main still picture. The main mode supports 8-bit color depth (i.e. 256 shades of red, green and blue, a total of 16.7 million colors), and the main 10 mode supports 10 bit color depth, which will be used on ultra high definition television (uhdtv). The first two limit the chroma sampling format to 4:2:0. It is expected that the standard will be expanded in 2014 and will support 4:2:2 and 4:4:4 sampling formats (i.e. providing higher color reduction), and multi view coding (e.g. 3D stereo video coding).
In fact, the h.265 and H.264 standards have some overlap in various functions. For example, the hi10p part of the H.264 standard supports 10 bit color depth video. Another part of H.264 (hi444pp) can also support 4:4:4 chroma sampling and 14 deeper than features. In this case, the difference between h.265 and H.264 is that the former can use less bandwidth to provide the same function at the cost of device computing power: the video encoded by h.265 needs more computing power to decode. At present, chips supporting h.265 decoding have been released - Broadcom released a Brahma bcm7445 chip at CES exhibition in early January this year. It is a four core processor using 28 nm technology, which can transcode four 1080p video data streams at the same time, or the resolution is 4096 × 2160 h.265 encoded UHD video.
H. The future of 265
For ordinary consumers, they are more concerned about how long it will take to buy a device that supports h.265/hevc decoding. It depends on many factors. Video card giants such as AMD and NVIDIA may integrate h.265 in a fairly short time, although many new functions have not been added to h.265. The first generation chip may only be applicable to the newly finalized standard. After future expansion, a version supporting h.265 multi view decoding will be made.
Because different companies have different decoding capabilities for H.264 video, we may see some "fooling people" information in terms of device level compatibility. For example, smart phones or tablets with powerful CPUs that can forcibly realize h.265 video decoding through computing power can be advertised as "supporting h.265 video decoding", and such "support" will sharply increase their power consumption when processing video. There will certainly be some unscrupulous companies that hype h.265 and regard this new video standard as a gimmick to distinguish the device level, so that they can sell videos that do not really support h.265 decoding to consumers who do not know the truth. In fact, these contents will be produced by major media and advertising companies, so the inside story is more complex.
At present, MPEG-2 is still the main standard used in cable TV and digital TV broadcasting. The good news is that the introduction of h.265 standard can eventually persuade radio and television companies to give up the old MPEG-2, because h.265 can reduce bandwidth consumption by 70-80% for the same content. This can easily support full hd 1080p broadcasting under the existing bandwidth conditions. On the other hand, TV broadcasters have few reasons to want to innovate, because most cable TV companies face limited competition in their target markets. For the purpose of saving bandwidth, satellite TV companies may take the lead in adopting the h.265 standard.
In the long run, the h.265 standard will become the choice of 4K and 8K resolutions for ultra high definition television (uhdtv). But there are other problems. At present, there is little video content with native 4K resolution. H. The completion of the 265 standard means that content owners now have a corresponding theoretical standard, but they do not have a unified way to transmit content. Sony is planning a 4K film digital transmission service for customers who buy Sony 4K TVs, and also launched a high-definition Blu ray DVD player called "mastered in 4K" this year. These 1080p films are converted from 4K digital master, and are expected to launch a better quality "near 4K experience" in the future.
Comparison of standard definition (SD), high definition (hd) and 8K resolution ultra high definition (UHD) video sizes
The Blu ray Disc Association is studying ways to support 4K resolution video in the Blu ray Disc standard, but it's not that simple. Theoretically, H.264 can have this function after expansion, but then the bit rate problem will surface. A 4K Blu ray movie encoded by H.264 needs much more storage space than the h.265 version of the same content, and its size can be up to more than 100g, while the existing players do not support 100-128gb high-capacity recordable rewritable optical disc (BDXL).
So far, there is still no proper solution to add 4K resolution video to the existing Blu ray standard without damaging its compatibility. Although updating to the h.265 standard does not need to improve the disc manufacturing process, it needs to manufacture a new player to play the new Blu ray disc. Although some players can play high-density discs, it also needs to check and upgrade the equipment.
Another big problem is the game console's support for the h.265 standard. Sony's PS2 and PS3 hosts have promoted the development of DVD and Blu ray standards. In theory, the upcoming PS4 is likely to support 4K resolution content, but how should 4K resolution video be transmitted and through which standards? This is still under discussion.
At present, we still need to be cautious and optimistic about the h.265/hevc standard. But one thing is certain: the h.265 standard will significantly reduce bandwidth consumption on the same content quality. With h.265, it will not be difficult to broadcast high-definition 1080p TV broadcasting and 4K video online, but only if Sony or other media giants can find a way to transmit these contents. At the same time, if the mobile device adopts the h.265 standard, its high power consumption when decoding video is also a problem that major manufacturers need to solve. Read the full text and the technology zone
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