H.265: the era of HD network video

In last August, Ericsson launched the first h.265 codecs. Six months later, ITU officially approved the adoption of the hevc/h.265 standard, the standard is fully referred to as high efficiency video coding. the 264 Standard has been greatly improved. H.265 is designed to transmit high-quality online videos with limited bandwidth. Only half of the original bandwidth is required to play videos of the same quality. This also means that our mobile devices (mobile phones and tablets) will be able to play full-definition (1080 p) videos directly online. The h.265 standard also supports 4 K (4096x2160) and 8 K (8192x4320) ultra-HD videos, the h.265 Standard keeps the online video behind the "High Resolution" of the display screen, probably within a few months, you can see that devices supporting h.265 decoding are listed (such as smartphones and video cards ). H.264 has ruled the past five years, and h.265 is likely to become the mainstream in the next five or even ten years.

Why h.265 is 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 codec, advanced video encoding), is a video compression standard, it is also a widely used high-precision video recording, compression, and publishing format. H.264 is well known for its codec standard. All Blu-ray players must be able to decode H.264. More importantly, Apple decided to abandon Adobe's VP6 encoding and chose H. 264, this standard has become an absolute leader in the video coding field, with hundreds of millions of iPad and iPhone entering thousands of households, accounting for more than 80% of the shares. H.264 is also widely used in network streaming media data, various high definition television Land broadcasting, satellite television broadcasting, and other fields.

H. compared with the previous encoding standards, 264 has some new features, such as motion compensation of Multi-reference frames, Motion Compensation of variable block size, and intra-Frame Prediction encoding. By using these new features, H. 264 has a higher video quality and a lower bit rate than other encoding standards, so it has been recognized by people.

The encoding architecture of h.265/hevc is roughly the same as that of H. 264/AVC architecture is similar, mainly including: intra prediction, inter prediction, transform, Quantization) deblocking Filter and entropy coding. However, in the hevc coding architecture, the whole is divided into three basic units, namely: encoding unit (Cu), prediction unit (PU) and the conversion unit (TU)
).

Compared with H. 264/AVC, h.265/hevc provides more tools to reduce the bit rate. For the encoding unit, H. in 264, the size of each Macro Block (marcoblock, MB) is fixed 16x16 pixels, while the h.265 encoding unit can be from the minimum 8x8 to the maximum 64x64. For example, the macro blocks in areas with a small amount of information (the color changes are not obvious, such as the red part of the car body and the gray part on the ground) are large, and the codes after encoding are less, where there are many details (Tires), the macro blocks are smaller and more, and there are more code words after encoding, which is equivalent to focusing on the image encoding, this reduces the overall bit rate and increases the encoding efficiency accordingly. In addition, h.265 supports 33 types of intra-frame prediction modes (H.264 only supports 8 types), 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 with h.265 will be reduced by about 39-264 compared with H.264. Due to the different quality control measurement methods, this data will also change accordingly. The data obtained through subjective visual testing shows that h.265 video quality can be consistent with h when the bit rate is reduced by 51-74%. 264 encoded videos are similar or even better, essentially better than the expected SNR. These subjective visual testing criteria cover many disciplines, including psychology and human visual characteristics. Video samples are very extensive, although they cannot be used as final conclusions, but this is also a very encouraging result.

Comparison between h.265 and h.265 video subjective visual testing, we can see that the bit rate of the latter is much lower than that of the former.

Currently, the hevc standard has three modes: Main, main 10, and main still picture. The main mode supports 8-bit color depth (256 colors for each of the red, green, and blue colors), and the main 10 mode supports 10 bit color depth, which will be used on uhdtv. Both of the preceding two sets the color sampling format. The standard is expected to be extended in 2014 and supports the and sampling formats (that is, higher color reduction) and multi-view encoding (such as 3D stereo video encoding ).

In fact, h.265 and H.264 standards overlap various functions. For example, the hi10p section in H.264 supports videos of 10 bit color depth. Another H.264 section (hi444pp) also supports 4-4 color sampling and 14-bit color depth. In this case, h.265 and H. the difference of 264 is that the former can use less bandwidth to provide the same function, and the cost is the computing power of devices: h.265 videos require more computing power to be decoded. At present, a Chip Supporting h.265 decoding has been released -- Broadcom released a Brahma bcm7445 chip at the CES exhibition in early January this year, it is a quad-core processor using a 28nm process. It can transcode four 1080p video streams at the same time, or parse h.265 encoded ultra-high-definition videos with a resolution of 4096x2160.

Future of h.265

For ordinary consumers, it is certainly not long before they can purchase devices that support h.265/hevc decoding. This depends on many factors. Graphics giants such as AMD and NVIDIA may integrate h.265 in a short period of time, although h.265 still has many new features. The first generation chip may only apply to the standards just finalized. After the expansion is completed in the future, a version supporting h.265 multi-view decoding will be created.

Because different companies have different decoding capabilities for H.264 videos, we may see some "dumb" information for device-level compatibility. For example, smart phones or tablets that have powerful CPUs that can forcibly perform h.265 video decoding Through computing power can be promoted to support h.265 video decoding ", such "support" will greatly increase the power consumption when processing videos. There will certainly be some unscrupulous companies that will publicize h.265 cloud and regard this new video standard as a gimmick to differentiate the device level, in this way, you can sell videos that do not actually 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 complicated.

Currently, cable TV and digital television broadcasting are mainly based on MPEG-2 standards. The good news is that the introduction of the h.265 standard could eventually persuade radio and television companies to give up the old MPEG-2, because of the same content, h.265 can reduce bandwidth consumption by 70-80%. This allows you to easily support full-definition P broadcast with the current bandwidth. On the other hand, television broadcasting companies have few reasons for innovation, because most cable TV companies face limited competition in their target market. To save 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 4 K and 8 K resolution for uhdtv. But this also brings about other problems. At present, there are very few native 4 K resolution video content. The completion of the h.265 standard means that the content owner now has a corresponding theoretical standard, but they do not yet have a unified way to transmit the content. Sony is planning a 4 k film digital transfer service for customers who buy Sony 4 k TV, and this year launched a high-definition Blu-Ray DVD player named "mastered in 4 K. These P films are converted from 4 K digital masters and are expected to provide a "nearly 4 K experience" with better quality in the future ".

SD, HD, and 8 K Ultra-HD (UHD) Video size comparison

The Blu-ray Disc Association is studying how to support 4 K resolution videos in the Blu-ray Disc standard, but this is not that easy. In theory, H.264 can have this function after expansion, but the bit rate problem will emerge at that time. One H. 4 K Blu-ray movies with 264 encoding require much larger storage space than h.265 versions with the same content, and the size can be larger than GB, the existing player does not support-GB of high-capacity, Erasable CDS (bdxl ).

Up to now, there is still no proper solution. You can add a 4 K resolution video to an existing Blu-ray standard without compromising its compatibility. Although it is not necessary to improve the CD manufacturing process to update the h.265 standard, it is necessary to create a new player to play the new Blu-ray disc. Although some players can play high-density CDs, however, you also need to check and upgrade the device.

Another major problem is the support for the h.265 standard for game hosts. Sony's pS2 and PS3 hosts drive the development of DVD and Blu-ray standards. In theory, the upcoming PS4 will probably support 4 K resolution content, but what standards should be used to transmit 4 K resolution videos? This is still under discussion.

We still need to be cautious and optimistic about the h.265/hevc standard. However, it is certain that the h.265 standard will significantly reduce bandwidth consumption in terms of the same content quality. With h.265, HD 1080p television broadcasting and 4 K video network playback, it will not be difficult, but the premise is that Sony or other media giants can come up with a way to deliver the content. At the same time, if mobile devices adopt the h.265 standard, the high power consumption during video decoding is also a problem that major manufacturers need to solve.

References

1. H.265 standard finalized, cocould finally replace MPEG-2 and usher in uhdtvJoel Hruska
2. Http://zh.wikipedia.org/wiki/H.264/MPEG-4_AVC
3. Http://en.wikipedia.org/wiki/High_Efficiency_Video_Coding
4. High-efficiency decision-making algorithm for hevc single-bit depth and simplified single-bit modeChen Heyuan

Source: http://www.guokr.com/article/436664/