What are the differences between H.264 and H.265 technologies?

At present, many cameras use the H.265 encoding standard, and H.264-encoded cameras are gradually reduced. Why is H.265 popular? What is the difference between H.264 and H.265?

What is H.265

H.265 is the new video coding standard developed by ITU-TVCEG following H.264. The H.265 standard revolves around the existing video coding standard H.264, retaining some of the original technologies and improving some related technologies. The new technology uses advanced techniques to improve the relationship between codestream, encoding quality, latency, and algorithm complexity to achieve optimal settings.

The specific research contents include: improving compression efficiency, improving robustness and error recovery capability, reducing real-time delay, reducing channel acquisition time and random access delay, and reducing complexity. H264 can achieve standard-definition digital image transmission at speeds lower than 1 Mbps due to algorithm optimization. The H265 can transmit 720P (1280 x 720) high-definition audio and video transmissions at speeds of 1 to 2 Mbps.

H.265 aims to transmit higher-quality network video under limited bandwidth, and only needs the original half bandwidth to play the same quality video. This also means that our smartphones, tablets and other mobile devices will be able to play 1080p full HD video directly online. The H.265 standard also supports 4K (4096×2160) and 8K (8192×4320) Ultra HD video. It can be said that the H.265 standard allows online video to keep up with the "high resolution" display.

What is H.264

H.264, which is also the tenth part of MPEG-4, is proposed by Joint Video Team (JVT) jointly formed by ITU-T Video Coding Expert Group (VCEG) and ISO/IEC Motion Picture Experts Group (MPEG). The highly compressed digital video codec standard. This standard is often referred to as H.264/AVC (or AVC/H.264 or H.264/MPEG-4 AVC or MPEG-4/H.264 AVC) and clearly describes its developers in both aspects.

The biggest advantage of H.264 is that it has a very high data compression ratio. Under the condition of the same picture quality, the compression ratio of H.264 is more than twice that of MPEG-2 and 1.5 to 2 times that of MPEG-4.

For example, if the size of the original file is 88GB, it will be compressed by MPEG-2 compression standard to 3.5GB, the compression ratio will be 25:1, and it will be converted to 879MB, from 88GB to 879MB, after being compressed by the H.264 compression standard. The compression ratio of H.264 reaches a staggering 102:1.

Low bit rate plays an important role in the high compression ratio of H.264. Compared with MPEG-2 and MPEG-4 ASP compression technologies, H.264 compression technology will greatly save users' download time and Data traffic charges. In particular, it is worth mentioning that H.264 also has high-quality and smooth images while having a high compression ratio. Because of this, H.264-compressed video data requires less bandwidth during network transmission. It is also more economical.

What is the difference between H.265 and H.264?

Before discussing the enhancements and advantages of H.265, we might as well take a look at H.264. H.264, also known as MPEG-4 AVC (Advanced Video Coding), is a video compression standard and is also a recording, compression, and distribution format for widely used high-precision video. H.264 is known as a codec standard for Blu-ray discs, and all Blu-ray players must be able to decode H.264.

More importantly, because Apple initially decided to abandon Adobe's VP6 code and chose H.264, this standard will also enter hundreds of millions of iPads and iPhones and become the current domain of video coding. Absolute overlord, with over 80% share.

H.264 is also widely used in network streaming media data, various high-definition television broadcasts, and satellite television broadcasts. H.264 has some new features compared to previous coding standards, such as motion compensation for multiple reference frames, variable block size motion compensation, intra-prediction coding, etc. By using these new features, H.264 has more advantages than other coding standards. High video quality and lower bit rate have also been recognized by people and widely used.

The coding architecture of H.265/HEVC is similar to that of H.264/AVC, and mainly includes: intra prediction, inter prediction, transform, and quantization. Deblocking filter, entropy coding and other modules. However, in the HEVC coding architecture, the whole is divided into three basic units, which are: a coding unit (CU), a prediction unit (PU), and a transform unit (TU).

Why H.265 is better than H.264

Compared to H.264/AVC, H.265/HEVC provides more different tools to reduce the code rate. In terms of coding units, the size of each macroblock (MB) in H.264 is a fixed 16x16. Pixels, and H.265 encoding units can choose from the smallest 8x8 to the largest 64x64.

Repeated quality comparison tests have shown that at the same picture quality, the H.265-encoded video stream size is reduced by about 39-44% over H.264 compared to H.264. Due to the different methods of quality control measurement, this data will also have corresponding changes. The data obtained through subjective visual testing shows that the quality of H.265-encoded video can be similar to or even better than that of H.264-encoded video at a code rate reduction of 51-74%, which is essentially better than expected. The signal to noise ratio (PSNR) is better. These subjective visual test evaluation criteria cover many disciplines, including psychology and human visual characteristics. The video samples are very extensive. Although they cannot be used as final conclusions, they are very encouraging results.

The current HEVC standard has three modes: Main, Main10, and Main Still Picture. Main mode supports 8-bit color depth (that is, 256 colors of red, green, and blue, and 16.7 million colors in total). The Main10 mode supports 10 bits of color depth and will be used in 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 extended in 2014 and will support 4:2:2 and 4:4:4 sampling formats (ie, provide a higher degree of color reproduction) and multi-view encoding (eg, 3D stereoscopic video encoding).

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. The other part of H.264 (Hi444PP) can also support 4:4:4 chroma sampling and 14-bit feature depth. In this case, the difference between H.265 and H.264 is that the former can use less bandwidth to provide the same functionality at the expense of device computing power: H.265-encoded video requires more computing power To decode. There are already chips supporting H.265 decoding. Broadcom has released a Brahma BCM 7445 chip at the CES exhibition in early January of this year. It is a quad-core processor with a 28-nm process. , You can transcode four 1080P video streams or H.265 encoded Ultra HD video with a resolution of 4096×2160.

The birth of H.265 standard is to transmit higher quality network video under limited bandwidth. For most professionals, the H.265 coding standard is no stranger to it. It is the video coding standard developed by ITU-TVCEG following H.264. The H.265 standard mainly revolves around the existing video coding standard H.264. After retaining some of the original technologies, the H.265 standard has increased the relationship between code stream, encoding quality, delay, and algorithm complexity. Related technologies. The main contents of the H.265 study include improving compression efficiency, improving robustness and error recovery capabilities, reducing real-time latency, reducing channel acquisition time and random access delay, and reducing complexity.

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