Over the past few years, it has been in the past few years, and the video applications such as on-demand, live broadcast, have achieved their own achievements. We combine users scenes in the business of on-demand, live, short video, etc., launched a "provincial bandwidth, pressure cost" series, starting from the coding technology, network architecture, etc., combined with the product outcomes of the cloud, introduce you to save traffic To reduce the coup of bandwidth cost.
This article "In-depth analysis of H.265 encoding mode, takes you to understand the reason for the H.265", is the second article of the "provincial bandwidth, pressure cost" series of articles. Depart from the problem encountered from the video website, analyze the H.265 video coding.
Previous review:
The first one: "Save more than 50% of the flow costs, from the product architecture, PCDN's throduct capacity"
The second: "In-depth resolution of H.265 encoding mode, take you to understand the reason for the H.265" APPL
Today we talk video codes. Video files have a contradiction: HD image quality and video volume conflict, with the same coding standard, video is higher, the video is larger. Therefore, to apply more advanced video coding standards, reduce video volume, can greatly reduce the traffic consumption of the website.
The most widely used video coding standard for application is H.264. The video quality of H.264 at low yield is very vague; the support of H.264 pairs 2K, 4K video is poor: with H.264 compression ratio, a volume of 4K movie will exceed 100g, and even achieve 150g, 200g, this is almost deadly blow to the video platform that wants to seize the source of HD.
It is necessary to have a high-definition, and the video volume is small - this is obviously impossible by H.264, and the new encoding format H.265 can meet this requirement. It is also a 4K video of 110 minutes, compressed with H.265, and the volume can be reduced by 50%, and each 4K video can save a large amount of flow bandwidth cost compared to 100G-200G of H.264.
H.265 is an internationally recognized next-generation video coding standard, and more and more support for H.265 at home and abroad, China does not only love Qiqiyi, Sohu, Tencent and other head video sites began to support H.265 video on demand The major subtitles groups have also begun to try to press video using the H.265 standard.
H.265: New generation video coding technology
H.265 video coding technology is published in 2013, which is named Hevc (High Efficiency Video Coding), which is adopted by ITU-T and ISO / IEC, namely H.265 video compression standard. . Based on the existing video coding standard H.264, H.264 further improves compression efficiency, improving robustness (Robustness anti-transformability) and error recovery capabilities, reducing real-time delay, reducing channel acquisition time and random access Delay, reduce complexity to achieve optimal settings.
H.265 can transmit higher quality network video at a limited bandwidth, only H.264's half bandwidth can transmit the same quality video.
1. The video compression ratio is more, and the compression efficiency is 1x compared to H.264.
H.265 New coding mode effectively improves the video compression ratio, only the original half bandwidth can play the same quality video. It is well known that the code rate of video encoding is flexible, with the same video quality as a baseline, H.265 encoding technique can reduce H.264 encoding technology to 39% to 74% in video capacity, and can also obtain ratio h .264 video better signal-to-noise ratio (PSNR) effect. - Take "volume than you small, quality than you" to describe H.265's huge advantage compared to H.264, did not look too much.
△ H.264, H.265 compression ratio comparison
2. Video transmission traffic is 50%
IEEE published in Circuits and Systems for Video Technology, which Comparison of the Coding Ef fi ciency of Video Coding Standards-Including High Ef fi ciency Video Coding article to 9 segments the video encoding performance test H.265, the results obtained are quite satisfactory alternative Even in the sample that is the worst, saving traffic is close to 30%, and the average is also up to 49.3%. △ H.265 and H.264 flow comparison
3. Support Blu-ray 4K
H.265 encoding technology has an amazing compression ratio, plus flexible macroblock pixel technology, which is extremely important for Ultra HD 4K / 8K ultra high-definition resolution. The Blu-ray 4K (3840 × 2160) standard in 2015 is officially introduced. H.265 / HEVC coding standard, H.265 encoding technology can significantly reduce the capacity requirements of Blu-ray 4K disc.
H.265 Compression principle
A larger macroblock and transform block: The H.265 has introduced 32 × 32, 64 × 64 or even 128 × 128 macroblocks in H.265. An object is to reduce the number of macroblocks of HD digital video, reducing parameter information for describing the contents of the macroblock, and the shaping conversion block size is also expanded accordingly, is used to reduce the similar coefficients of the change in phase neighboring block in H.264.
△ H.264 and H.265 contrast
New MV (Sports Vector) Prediction: Different from H.264 Based on the Sport Vector Prediction Mode of Spatial Domain, the H.265 expands more direction for intra prediction, and the set of predictive blocks is extended by the original spatial domain to Time domain and empty mixed domain, select the best predictive block after the rate of distortion criteria. Using this method, in the basic mode, in the case of the same quality as H.264, the compressed gain of 6.1% is obtained, and the compression gain of the complex image can even be increased to 20%.
Parallelization: The current chip architecture has gradually developed from single core performance, and H.265 introduces ENTROPYSLICE, WPP and other parallel operation ideas, using a higher degree of encoding algorithm, more beneficial to H.265 in GPU / DSP / FPGA / ASIC is highly efficient in CPUs to achieve industrialization.
TILE division mechanism: It makes the coarse granular data parallel mechanism in the past slice, frame or GOP, more suitable for parallel implementation on the holy multicore processor. The DependentSlice and WPP mechanisms solved the problem of entropy encoding links in the previous coding technique in the past, making the DCT, motion estimation, motion compensation, entropy coding, and other task modules in the entire codec process more balanced, significantly improved parallelism. Speedup ratio.
Open H.265 Adaptation
Compared with H.264, H.265 is not only a trend of future HD movie development, but also to provide more efficient video compression efficiency, effectively saving traffic consumption in the same picture quality.
In order to allow users to use more advanced products, it has been drilled in the practicality and convenience of H.265, and H.265 video adaptive solution is launched in May 2017. Also shoot cloud H.265 video adaptive solution integrates video upload, video storage, video coding (transcoding), video distribution, video decoding and other functions.
Video transfer code: User to upload H.264 encoded video to another cloud server, and shoot it synchronously into H.265 encoded video; video asynchronous transcodation: for stored in the cloud server H.264 encoded video, through the cloud asynchronous transcoding service, can be converted to H.265 video storage, while retaining H.264 video copy; H.265 adaptive: also shooting cloud CDN network support H.265 adaptive Function, the UA request header initiated according to the client terminal player (Accept-Encoding: H265), whether the intelligent identification terminal player supports H.265, and determines whether the currently requested resource has a file encoded by H.265. If the player supports and has a video encoded by H.265, return H.265 video, otherwise returning the original video, thereby implementing the H.265 intelligent adaptation of the CDN platform. H.265 Adaptive Support is also a cloud storage and a cloud CDN.
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[Provincial bandwidth, pressure cost] How does PCDN will thrift 50% from a product architecture?
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