From this article, we will introduce H.264 / AVC. In the first few, we introduced MPEG-1 and MPEG-2, and considering it in order, we should ask questions, should it be MPEG-3? That's true, in fact, MPEG-3 is indeed, it is after MPEG-2, the audio and video standards that are developed on HDTV. However, since MPEG-2 is successful, it is already possible to meet the demand, so MPEG-3 is fused into MPEG-2.
Then we should have questions, then it should not be H.264 / AVC, it should be MPEG-4, which involves our topic today. So before talking about H.264 / AVC, let's talk about MPEG-4.
1, MPEG-4
MPEG-4 is also known as the Coding Of Audio-Visual Objects standard, pay attention to MPEG-1 and MPEG-2, it is more objects. It not only absorbs many of MPEG-1 and MPEG-2, but introduces the concept of audio-visual objects encoding. Here we don't have to manage what to listen to the object, because it does not appear in the next H.264 / AVC. why? This involves the components of MPEG-4.
Just like MPEG-1 and MPEG-2, MPEG-4 consists of multiple parts. Because MPEG-4 applications, it released the second edition in 1999, and officially became an international standard in 2000, and even now, it is constantly updated and improved. Introduction This paragraph is not to explain that MPEG-4 has more cattle, but for explanation, for this, multiple parts of MPEG-4, there are also first. For example, Part 1 and Part 31, Part 1 are definitely the earliest release, and Part 31, until recently, is released in 2014.
MPEG-4 is not just a audio and video codec standard, it is still a multimedia application standard. Its content includes, audio and video codec, subtitle flow text format, font compression, 3D graphic compression, web video coding, etc. This shows that the range of MPEG-4 is wide, because of its research topics, most people will not learn. For example, we only care about the audio and video encoding portion, and this part of the corresponding Part 2 (Visual), Part 3 (Audio), Part 10 (AVC), Part 14 (MP4), of course, for MPEG-4 It will also look at Part 1 (System), which is the system part.
Note that Part 2 and Part 3 are respectively the video and sound portions, and these two parts are also included in the earliest release. And the object code we said earlier is applied in Part 2 (Visual). So when we say MPEG-4 visual object coding, generally refer to MPEG-4 Visual, which is ISO / IEC 14496-2 Part2, where 14496 refers to the number of MPEG-4 standards, 2 is only Part 2, join It is 14496-2. As shown below:
The figure is bidding the red frame, is the first time of their first release, can be traced back to 1999, which is the second edition of MPEG-4.
However, we are not prepared to put energy on MPEG-4 Visual, because in today's practical applications, H.264 / AVC is more popular. The first few of us speak MPEG-1 and MPEG-2 because they can provide help to understand H.264 / AVC, but MPEG-4 Visual includes knowledge of new object coding, understanding H.264 / AVC help Smaller, so we directly ignore, interested, you can read the information. Let's start introducing today's protagonist: H.264 / AVC
2, H.264 / AVC
Some students may feel that the jump is a bit fast, just still saying MPEG-4, how can I jump to H.264 / AVC. First of all, this feeling is normal because I haven't introduced a key information yet. Starting from this article, we have been writing H.264 and AVC when he is talking about H.264 / AVC, which is actually directly meaningful to its origin.
When we talked about several important parts of MPEG-4, we also have Part 2, Part 3, and Part 10 (AVC) and Part 14 (MP4), PART 14 will know, this is not The famous MP4 format (with the MP4 we will introduce). And another Part 10, behind the note is AVC, is it related to H.264 / AVC?
Well, yes, you guessed, the fact is true.
MPEG-4 Part 10
This is Wikipedia, about the introduction of MPEG-4 Part 10, please look at the red box note section: a video signal compression format, which is the same as ITU-T H.264. And AVC means that Advanced Video Coding is also advanced video coding. It was released in 2003, which is also fit in MPEG-1, the displayed annual table is also accompanied:
International video code
In this way, ITU-T H.264 and MPEG-4 AVC is actually a standard. The reason is a standard because it is an expert group of ITU-T vceg (Video Coding Experts Group, and the MPEG expert group, which is developed, thus generating a name of H.264 / AVC.
H.264 / AVC application is very wide, it can use the original RGB or YUV pixel data, encoded to H.264 bare stream, and based on H.264 bare stream, we can also package it into MP4, MKV and other formats to save to Locally, you can also package the transfer protocol to transmit on the Internet. This is the current mainstream application of H.264 / AVC. Of course, this paragraph doesn't understand, because we just look at the knowledge path in front of the front.
H.264 / AVC compared to the previous coding standard, such as MPEG-1, MPEG-2, has no significant change in structure. But its coding efficiency is much higher than them, why? That is because H.264 / AVC has made a lot of improvements in the previous standard, especially in each major functional module. Although these changes are not large, these improvements have become the essence, and the compression efficiency of H.264 / AVC is 2 to 3 times the MPEG-2. Effectively reduces the cost of transmitting video data on the network, and the DVD and digital television of MPEG-2 are previously used, and also turned to H.264 / AVC.
Below is the main improvement of H.264 / AVC:
(1) Inter Bloom Prediction: The inter prediction and movement compensation of variable drawing blocks, pay attention to the variable graphics, the previous standard predictive block size is 16x16 pixels, and after the improvement, the prediction diagram can be small to 4x4 Pixel. In this way, the prediction accuracy of the moving vector is improved.
(2) Inframe prediction: The size of the intra prediction diagram block is improved into a macroblock that can be 16x16, or may be a 4x4 pixel piece, and a variety of prediction methods are defined. In this way, it is to find the best matching predictive block.
(3) Adopt integer transformation: This is a transformation that evolves from DCT, which can improve the speed of operation.
(4) Entropy encoding with CAVLC and CABAC: Names do not need to be entrusted, just know that they are entropy encoding, and can be higher than the coding efficiency of VLC (variable length coding / variable length encoding).
(5) Filtering technology using multi-reference frame and eliminating block distortion: Block distortion means that when the compression ratio is too high, the reconstructed image will appear block appearance. The filtering technology used to eliminate this phenomenon, if you don't plan to learn digital image processing, you can do not need to manage it.
It can be seen that although these improvements are not very moving, each of them has a big effect. In particular, the predictive blocks of the first 1, 2, 16x16 can be small to 4x4, which will greatly improve the forecasting accuracy of the mobile vector, which affects a set of predicted images, which is the power of butterfly effect!
Our other product:
