Android IOS WebRTC Audio Video Development Summary (71)--What's the difference between h265/h264

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h.265

H.265 is the new video coding standard developed by ITU-TVCEG after H. The h.265 standard revolves around the existing video coding standard, which retains some of the original technology while improving some of the relevant technologies. The new technology uses advanced techniques to improve the relationship between code flow, encoding quality, latency and algorithmic complexity to achieve optimal settings. The specific research contents include: Improve compression efficiency, improve robustness and error recovery ability, reduce real time delay, reduce channel acquisition time and random access delay, reduce complexity and so on. H264 because of the algorithm optimization, can be less than 1Mbps to achieve SD Digital image transmission, H265 can be achieved by 1~2mbps transmission speed to transmit 720P (resolution 1280*720) normal HD audio and video transmission.

The h.265 is designed to deliver higher-quality network video at limited bandwidth, with only half the bandwidth available to play the same quality video. It 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 (4096x2160) and 8K (8192x4320) Ultra HD video. It can be said that the H.265 standard allows network video to follow the display "high-resolution" footsteps.
　　
h .
　　
H. MPEG-4, also part tenth, is a joint video group composed of the ITU-T video Coding Expert Group (VCEG) and ISO/IEC dynamic Imaging Expert Group (MPEG) (jvt,joint Team) proposed standard for highly compressed digital video codecs. This standard is often referred to as H.264/AVC (or avc/h.264 or H.264/MPEG-4AVC or mpeg-4/h.264 AVC) and clearly describes its two developers.
　　
The biggest advantage is the high data compression ratio, in the same image quality conditions, the compression ratio of H. MPEG-2 is more than twice times, is the MPEG-4 1.5~2 times. For example, if the original file size of 88GB, using MPEG-2 compression standard compression into 3.5GB, compression ratio of 25:1, and the compression standard of H. 102:1 to 879MB, from 88GB to 879mb,h.264 compression ratio to achieve a staggering. The low bit rate, which plays an important role in the high compression ratio of H. MPEG-2 and mpeg-4asp compression technology, will greatly save users ' download time and data traffic charges. In particular, it is worth mentioning that the high compression ratio at the same time, but also has a high quality smooth image, because of this, after the compression of the video data, in the network transmission process requires less bandwidth and more economical.
　　
What is the difference between h.265 and H .
　　
before we discuss the advantages and benefits of h.265, let's take a look at H. Also known as MPEG-4AVC (Advanced video Coding), it is a video compression standard and a widely used recording, compression, and publishing format for high-precision video. Since it is known as a codec standard for Blu-ray discs, all Blu-ray players must be able to decode H. More importantly, as Apple resolutely abandoned Adobe's VP6 code and chose H. Hundreds of millions of, the standard has gone into the tens of thousands of millions of ipads and iphones, making it the absolute overlord of the video coding field, with a share of over 80%. It is also widely used in the field of network streaming media data, various HDTV broadcasting and satellite TV broadcasting. Compared with the previous coding standards have some new features, such as multi-reference frame motion compensation, variable block size motion compensation, intra-frame prediction coding, through the use of these new features, H. A higher video quality and lower bitrate than other coding standards, but also by people's recognition, and is widely used.

H.265/HEVC's coding architecture is broadly similar to the architecture of the H.264/AVC, including: Intra-frame prediction (intra prediction), inter-frame prediction (inter prediction), conversion (transform), quantization ( Quantization), Block filter (deblocking filter), Entropy coding (entropy coding) and other modules. However, in the HEVC coding architecture, the whole is divided into three basic units, divided into: encoding units (coding UNIT,CU), predictive units (predict Unit,pu) and conversion units (transform Unit,tu).
　　
Why h.265 is better than H .
　　
compared to H.264/AVC,H.265/HEVC provides a number of different tools to reduce the bitrate, in terms of coding units, each macro block (MARCOBLOCK,MB) size is fixed 16x16 pixels, The H.265 encoding unit can choose from the smallest 8x8 to the largest 64x64. The area of information is not much (color change is not obvious, such as the red part of the car body and the gray part of the ground) divided the macro block larger, coded code word less, and the details of the place (tires) divided the macro block of the corresponding small and more, encoded code word more, this is equivalent to the image has been focused on coding, Thus reducing the overall rate of code, coding efficiency is correspondingly improved. At the same time, h.265 's intra-frame predictive mode supports 33 directions (only 8 are supported) and provides better motion compensation processing and vector prediction methods.
　　
repeated quality comparison tests have shown that the size of the video stream encoded by h.265 is about 39-44% less than that in the same image quality compared to H. because of the different methods of measuring quality control, the data will change accordingly. According to the data obtained by the subjective visual test, the quality of the h.265 encoded video can be approximated or even better than that of the encoded video in the case of the rate reduction 51-74%, which is, in essence, better than the expected signal-to-noise ratio (PSNR). The judging criteria for these subjective visual tests cover many disciplines, including psychology and human visual characteristics, and the video samples are very broad, although they cannot be used as final conclusions, but this is also a very encouraging result.
　　
the current HEVC standard has three modes: Main, MAIN10, and main still picture. The main mode supports 8bit color depth (that is, red, green, and blue three colors each have 256 chroma, a total of 16.7 million colors), Main10 mode support 10bit color depth, will be used in ultra-high-definition TV (UHDTV). The first two limits the chroma sampling format to 4:2:0. It is expected that the standard will be expanded in 2014 and will support the 4:2:2 and 4:4:4 sampling formats (i.e. providing higher color reduction) and multi-view encoding (e.g. 3D stereo video encoding).
　　
In fact, the h.265 and the H: standard have some overlap in various functions. For example, the hi10p section of the H. 10bit standard supports video with a color depth. The other, part of H. 14 (hi444pp) can also support 4:4:4 chroma sampling and a characteristic depth of more than a few (.). In this case, the difference between h.265 and H. S is that the former can use less bandwidth to provide the same functionality, at the cost of Device computing power: H.265 encoded video requires more computing power to decode. A chip that supports h.265 decoding has been released--Broadcom at the CES exhibition in early January this year released a Brahma BCM 7445 chip, a four-core processor with a 28-nanometer process, You can transcode up to four 1080P video streams or h.265 encoded Ultra HD video with resolution of 4096x2160.
　　
the birth of the h.265 standard is the transmission of higher quality network video at limited bandwidth. For most professionals, the h.265 coding standard is not unfamiliar, it is itu-tvceg after the development of the video coding standards. The h.265 standard mainly revolves around the existing video coding standard, which, in addition to preserving some of the original technologies, increases the correlation between the code stream, the encoding quality, the delay, and the complexity of the algorithm. The main contents of h.265 research include improving compression efficiency, improving robustness and error recovery ability, reducing real time delay, reducing channel acquisition time and random access delay, and reducing complexity.

Android IOS WebRTC Audio Video Development Summary (71)--What's the difference between h265/h264