H.265 is a new video coding standard developed by ITU-T VCEG after H.264. The H.265 standard revolves around the existing video coding standard H.264, retaining some of the original technologies, while improving some related technologies. The new technology uses advanced technology to improve the relationship between code stream, encoding quality, delay and algorithm complexity to achieve optimal settings. The specific content includes: improving compression efficiency, reducing real-time delay, reducing channel acquisition time and random access delay, and reducing complexity. Due to the optimization of the algorithm, H.264 can realize standard-definition digital image transmission at a speed lower than 1Mbps; H.265 can realize the transmission of 720P (resolution 1280×720) ordinary high-definition audio and video transmission at a transmission speed of 1~2Mbps.
H.265 technology (type) analysis
The R&D purpose of H.265 can be seen from its naming. H.265 is also known as HEVC (High Efficiency Video Coding), and its main purpose is to further reduce the amount of traffic required by the movie to reduce storage. And the cost of transmission. H.265 requires that in the best encoding profile (profile), it can save about 36% of the data volume of the 1080P surveillance video compressed with H.264 while maintaining the same PSNR, and it can save the data when the image quality is about the same. The savings are further increased to 50%.
In addition, H.265 restricts the amount of calculation required for compression and decompression. The time required for H.265 encoding with the best encoding template can only be 10% longer than H.264 encoding, and the decoding time It can be 60% more.
What are the advantages and differences between H.265 and H.264 and other technologies
Compared with H.264, the algorithm complexity of the H.265 standard has been greatly improved to obtain better compression performance. H.265 has made great improvements in many features (see Table 1).
In summary, the technical highlights of H.265 are:
Flexible coding structure: In H.265, the size of macroblocks is expanded from 16×16 of H.264 to 64×64 to facilitate high-resolution video compression;
Flexible block structure-RQT (Residual Quad-tree Transform). RQT is an adaptive transform technology. This idea is an extension and expansion of the ABT (Adaptive Block-size Transform) technology in H.264/AVC. For inter-frame coding, it allows the size of the transform block to be adaptively adjusted according to the size of the motion compensation block; for intra-frame coding, it allows the size of the transform block to be adaptively adjusted according to the characteristics of the intra-frame prediction residual Adjustment. Compared with the transformation of small blocks, the transformation of large blocks can provide better energy concentration effect on the one hand, and can save more image details after quantization, but on the other hand, it will bring more ringing after quantization effect. Therefore, according to the characteristics of the current block signal, the size of the transform block is adaptively selected to obtain the optimal compromise between energy concentration, detail preservation and the ringing effect of the image;
Sample Adaptive Offset. SAO is located in the codec loop, after Deblock, by classifying the reconstructed image, adding or subtracting an offset to the pixel value of each type of image to achieve the purpose of reducing distortion, thereby increasing the compression rate and reducing the code stream. After adopting SAO, the code stream can be reduced by 2%~6% on average, while the performance consumption of the encoder and decoder is only increased by about 2%;
Adaptive Loop Filter (Adaptive Loop Filter). ALF is located in the codec loop, after Deblock and SAO, and is used to restore the reconstructed image to achieve the minimum mean square error (MSE) between the reconstructed image and the original image. The coefficients of ALF are calculated and transmitted at the frame level. ALF can be applied to the entire frame, or ALF can be performed on a partial area based on a block or a quantization tree (quadtree). If it is ALF based on a partial area, the indication area information must be transmitted Additional information;
Parallel design. The current chip architecture has gradually evolved from single-core performance to multi-core parallelism. Therefore, in order to adapt to chip implementations with a very high degree of parallelization, HEVC/H.265 has introduced many optimization ideas for parallel computing.
H.265 technology development (bottlenecks and future development trends) analysis
In the surveillance industry, H.265 has been supported by many chip solution providers, but from the actual market, H.265 products are still very few. If the completed project is replaced with a H.265 network camera, the corresponding back-end storage also needs to be replaced with a product that supports H.265. In this case, the overall project transformation investment is too large.
For new projects, H.265 is still a relatively new technology, and various security manufacturers basically incorporate H.265 into their high-end product lines, so the overall cost of new projects is also higher than the equipment investment using H.264.
In fact, judging from the current layout of the entire surveillance industry, H.265 is more suitable for occasions like 4K/8K. Higher resolution, lower bandwidth. Using H.265 can reduce the original bandwidth by at least 50%, whether it is network transmission or back-end storage space can get a lot of help.
At the same time, news on the Internet pointed out that HEVC (High Efficiency Video Coding, or H.265) is natively built in the Microsoft Windows 10 operating system, that is, 4K or 8K videos can be played efficiently through the Windows 10 system.
As a new generation of video coding technology, H.265 has the unparalleled advantages of previous generations of coding technologies, such as MPEG-4, H.264, etc. That is, there is currently no compression technology that can compete with it, so compatibility is also very important. Big advantage. In short, H.265 will greatly promote the rapid development of video applications including high-definition video.
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