Day 1-resolution of HD video Encapsulation Format

Zol HD Lecture Hall: HD video Encapsulation Format Parsing http://it.southcn.com/9/2011-02/11/content_19899035_3.htm in order to make you more understand the knowledge of HD, enjoy the quality of HD more perfect life, zol launched a high definition lecture hall, I hope that I can provide some users with experience with high definition in their daily lives. In the last issue, I introduced the problem of video encoding, this time, I will introduce you to the encapsulation format that is closely related to video encoding. Click the zol HD lecture hall in the previous issue: Comprehensive Analysis of video encoding formats

Video Encoding is an algorithm for compressing videos, and the video Encapsulation Format is the file type we have seen. Therefore, the video Encapsulation Format must be a "familiar stranger ". The videos we use, including the videos we have downloaded from the Internet to be watched in audio and video software or player, and files in our mobile phones, MP4, and other playback devices, in people's discussion, we basically talked about the video formats that a mobile phone can play. The format in the mouth refers to the "Encapsulation Format", which is the already formed file type. We get to him every day, but we don't necessarily know him. Today, I hope you will have some gains after reading this high definition lecture.

Video Encapsulation Format

In fact, it is necessary for us to understand the video encapsulation format in the future. In the last issue, we learned about the video encoding methods, which is a prerequisite for us to understand the Encapsulation Format, we have learned about the Encapsulation Format in this issue and will be helpful in choosing the playing equipment and screening the playing performance of the machine in the future. In addition, mobile phones, tablets, and multimedia on computers have become mainstream in our daily lives. It is even more necessary to know more about this aspect. In home entertainment, if you want to make your home theater a powerful "nothing to play" device, you should be more energetic.

  How does one understand the video Encapsulation Format?

I have randomly asked people of all ages in all walks of life about their cultural levels and found that few people who are in contact with videos can clearly identify video encoding and encapsulation formats. The main reason is that, on the one hand, video encoding and encapsulation formats are complicated and complex. On the other hand, many people do not pay much attention to the collection of this knowledge and there are many self-righteous mistakes. Here I will answer them one by one.

　　1. What is the Encapsulation Format?

The so-called Encapsulation Format is to put the compressed video track and audio track into a file in a certain format, that is, it is just a shell. Here are two examples for your understanding. There are two animated images in a bottle. We can use this bottle as a encapsulated video with compressed videos and audio. To watch a video with both sound and image, we need a container to "encapsulate" the video and audio and present them together. For example, a zip file is a container that can contain various types of files, such as images or Word files. the same is true for encapsulation formats such as MKV and Avi,
It can contain videos of different encoding formats.

Encapsulate a file like a bottle

Originally, the original video stream data is converted into a corresponding bit stream after being encoded, And the bit stream is encapsulated into the corresponding file format according to the protocol. The so-called encapsulation is to add different "headers" to the original video bit streams and cut them into different sizes. For example, after the original analog video adopts MPEG2 digital encoding, you can use TS Stream format to encapsulate it into TS Stream files, or PS stream format to encapsulate it into PS stream files, the option is you. TS stream is called a real-time stream. It divides video information into many small packages and damages a package, when decoding and playback, you only cannot see a small part (such as mosaic), but PS streams are file streams. If the file is damaged, the entire file cannot be viewed. Again, the encapsulation of a video resource using Ts streams is to cut the video into 10 parts and put it in 10 boxes. One box is opened in order, you can watch this video. The PS stream puts the entire video in a box and it will automatically play it for you in order. If one box is broken, the TS stream can see nine boxes, and you will not be able to see the PS. (From the Internet)

　　Ii. How to identify the Encapsulation Format

Some people may say that I understand what the video Encapsulation Format is, but how can I tell what the video format is? In fact, I would like to tell you a clear method. The suffix after each video file is the Encapsulation Format of the video. In fact, the Encapsulation Format is just a professional formal name. Currently, the following video encapsulation formats can be encapsulated for p hd videos: MP4, Avi, MKV, ts, and mov.

  Introduction to major HD movie encapsulation formats

　　1. Avi Encapsulation Format

Avi has already been recognized by international professional organizations and academic institutions as a packaging format that has been outdated and eliminated, we always see the image in AVI format in a variety of videos, so we will also introduce it.

Avi Encapsulation

Avi was a Technology launched by Microsoft in 1992. It was originally designed to combat Apple's QuickTime technology. Although we have no technical advantages at present, there are still many supporters because of the versatility of windows and easy-to-understand API development.

Like all encapsulation formats, Avi only provides a shell and a framework. Theoretically, the encoding formats of internal video and image data and the Audio Encoding formats should be arbitrary. However, in the Internet era, streaming media can no longer be played over the Internet. For example, if the resources downloaded on the network fail to reach 100%, there is no way to play back the resources.

Another problem is that Avi does not support high-bit-rate VBR audio files.

The full name of VBR is variable bitrate, which is the dynamic bit rate. Different bit rates can be defined according to the current needs to avoid waste and improve the utilization. The problem arises as the image in the container is separated from the sound, so a synchronization process between the image and the sound is required during playback. If the CBR audio track is set, synchronization is not a problem, but the VBR audio tracks are constantly changing, while Avi does not have time to intercept the VBR audio tracks and images, which leads to the problem of non-synchronous image sounds. (From Baidu encyclopedia http://wenku.baidu.com/view/6cc8fb0e52ea551810a687d2.html)

Later, virtualdub proposed a new method to expand Avi's compatibility with VBR audio. It was previously recognized as a cracking, but it has recently been gradually recognized by academia, it has become a means to expand the AVI technology. To put it simply, vbrs are divided into equal blocks through redundant data transformation packages to simulate CBR. However, this method also has limitations. Only a part of the VBR sound compression method can be used, and the audio data must be analyzed in detail to determine the maximum redundancy for each compression format, if the audio quality bit rate is high, the encoding efficiency will be poor and it is difficult to implement. However, when the bit rate is high, the loss of data will occur, resulting in lossy sound effects. This problem has not yet been a perfect solution. What's more, many of them are completely unsupported (truehd,
DTS-HD master audio ). So we often see that Avi is good, and the sound quality problem is only because the data volume of some audio tracks is too large and the player cannot be put.

2. Ts Encapsulation Format

Speaking of the TS Encapsulation Format, we have to mention the hddvd that has exited the historical stage. Although both hd dvd and BD adopt MPEG2/VC-1/H.264 in encoding, the Encapsulation Format is different. The hd dvd officially recognized by the DVD Forum uses the PS encapsulation, that is, the Program Stream (Program Stream), which is the same as the MPEG2 Program Stream encapsulation used in the previous DVD, the suffix of the PS stream is vob and Evo. Without the official certification of the DVD Forum, BD uses ts encapsulation, namely transport stream, instead of PS encapsulation ), the suffix of the TS stream is ts. Because BD wins in the competition, we now commonly use the TS Encapsulation Format.

TS encapsulation container

After the original analog video adopts MPEG2 digital encoding, You can encapsulate it into a TS Stream file in the TS Stream format, or you can encapsulate it into a PS stream file in the PS stream format, a ts stream is called a real-time stream. It divides video information into many small packages and damages a package. When decoding and playback, you only cannot see a small part (such as mosaic ), however, the PS stream is a file stream. If the file is damaged, the entire file cannot be viewed. Again, the encapsulation of a video resource using Ts streams is to cut the video into 10 parts and put it in 10 boxes. One box is opened in order, you can watch this video. The PS stream puts the entire video in a box and it will automatically play it for you in order. If one box is broken, the TS stream can see nine boxes, and you will not be able to see the PS. (Internet)

We will focus on the TS Encapsulation Format. TV programs can be decoded (watched) when you turn on the TV, the characteristic of the MPEG2-TS format is that it can be decoded independently from any part of the video stream. In terms of structure, TS consists of the header file and the subject, and the expanded TS Stream also contains the timestamp. In this way, regardless of the format of the VBR audio track, it is easy to use the time stamp to synchronize the image. Of course, for the new sound format, a new separator and decoder are required for decoding. It is constantly improving development. Unlike Avi, TS has taken network playback into account since its birth. As a result, it soon became a world standard and widely used in TV station digital playback, mobile phones, and other fields.

　　3. MpEG Encapsulation

Mpg, also known as Moving Pictures Experts Group, is a dynamic image Expert Group. It was jointly established in 1988 by the International Standardization Organization ISO (International Standards Organization) and IEC (International Electronic Committee, it is dedicated to the standardization of motion images (MPEG videos) and audio companion codes (mPEG audios.

MPEG is an international standard for Motion Image Compression Algorithms and is now supported by almost all computer platforms. It includes MPEG-1, MPEG-2 and MPEG-4. MPEG-1 is widely used in the production of VCD (video compact disk), the vast majority of VCD adopts MPEG-1 format compression. MPEG-2 is used in the production of digital video/versatile disk, HDTV (high definition television broadcasting) and some demanding video editing and processing.

MP4 (also called MPEG-4) is an MPEG format, is a compression method of active images. Through this compression, small files can be used to provide higher image quality. It is one of the most popular video file formats (especially on the network. The advantage of this format is that it can not only cover low-frequency bands, but also develop to high-frequency bands. Since its publication, MP4 has aroused widespread attention. Currently, the most popular compression methods for MP4 are DivX and XviD. After a DVD program processed by MP4 technology, which is represented by DivX or Xvid, the quality of the video and audio in the image has not decreased much, but the volume has been reduced to a fraction of the original, it is easy to save the generated file with two MB-size normal CD-ROM. A single disk can accommodate a movie of one hundred minutes, and the image quality is obviously better than that of VCD. The file extension of an MPEG Video is usually MPEG or mpg.

　　4. MKV Encapsulation Format

MKV is a new file format with distinctive advantages: it can be flexibly used with any video and audio encoding, just like a deformation universal packing box. Any video encoding file can be put into MKV, of course, the latest H. 264 is the most popular. any audio encoding file can also be put into MKV, and n Different audios can be put in a movie. For example, one audio is a Chinese dubbing dual-channel, and one audio is a 5.1 stereo sound in English, the other is the 7.1 surround sound in Japanese. Each sound is essentially different from the left and right audio channels used by VCD many years ago.

Even better, you can put multiple Subtitles into MKV. in this way, you can switch Subtitles at will during viewing. Anyone in any country can understand la .mkv. Currently, it is widely used on computers, but it is not widely supported by hosts. thanks to the obvious advantages of MKV, the new DVDRip and bluediscrip all use MKV encapsulation in large quantities, and even surpass the official MP4 encapsulation trend. in the MKV package, the most accepted video and audio encoding methods are: H. 264 (x.264) video with AAC audio.

  Several problems that are easy to pay attention:

　　I. What are the advantages of MKV over Avi:

Compared with Avi, it has the following advantages:

1: Variable Frame Rate: This requires encoding. Imagine replacing it with low FPS when playback changes are slow (for example, static objects), which can save a lot of resources.

2: Error Detection and repair: This undoubtedly provides error correction and fault tolerance, which is especially required during network transmission.

3: Soft Subtitles: Friends who often read DVDRip and hdrip know that Subtitles generally exist in the form of other files. In MKV, subtitles can be embedded in encapsulation, but will not be confused with videos, you can also select multiple Subtitles at will. This makes transmission and storage easier.

4: stream transmission: this is basically the same as the reason for TS stream. You can use timestamps to manage video and audio synchronization issues, so that you can watch the video right away.

5: menu: Interactive operations make MKV more user-friendly.

6: strong compatibility: The biggest feature of MKV is that it can accommodate a variety of different types of encoding video, audio, and Subtitle streams. Even the very closed RealMedia and QuickTime are included in it, A universal media container.

7: openness and cross-platform: matroska uses an open architecture with many advanced features and can be used across platforms.

Ii. How to compare the definitions of MKV and Avi?

1. Who has smaller MKV and AVI sizes with the same resolution?

If you can understand the analogy above, you should know that this question does not make much sense. The key to the size of the video is the size of the video. If the same content is encapsulated, the size is almost the same.

2. Who has a higher definition of MKV and AVI in the same volume?

In the same way, this problem is meaningless. The definition depends on the content encapsulated in MKV and Avi. If MKV encapsulates 720 p and AVI encapsulates 1080 p, which one do you think is clear? If the same is true.

3. Who is more fluent in MKV and AVI with the same definition?

Avi is relatively suitable for older machines. If your configuration is not very good, it may be appropriate to play Avi. Of course, it also depends on the separator and decoder used for playing.

4. In the case of the same smooth playback, the video interface is reduced and zoomed in. Who has a lower error rate in MKV and Avi?

As with the previous issue, if there is a false positive rate, it is also generated by the player and decoder used. More is the result of psychological effects.

"The definitions of MKV and Avi are the same on the materials read on the internet." First, there is a problem with this sentence. MKV and Avi are only encapsulation methods, definition cannot be determined. The definition mainly depends on the unclear source. Just like water in a glass water tank, if you want to show people a clear feeling, the most important thing is that the water inside is clean. That is to say, only the small and clear size of the compressed video will affect the quality of the video image, but it has little to do with the Encapsulation Format.

Of course, the encoding method during encapsulation is also somewhat related, but the gray scale of the same chip is a little different. Currently, MKV is mainly based on x264 encoding, while Avi is mostly based on DivX encoding, divX encoding has seen a large number of films earlier, but most of the current mainstream uses the x264 encoding in MKV encapsulation, because this method does not significantly reduce the image size, it seems that the color is more "real", so the film from the same source feels more natural and will be checked. So you will feel "MKV is much clearer than Avi ". Of course, the x264 encoding can also be encapsulated with Avi. The compressed parts are the same as the x264 encoding and the MKV encapsulation, but few people do this. It is a bit difficult to hear, of course, the benefit of AVI format is that you can see thumbnails in windows.

The size of a piece in the MKV and AVI formats does not exist. It mainly depends on how high the bit rate is used during encoding. The higher the bit rate, the larger the file, the higher the bit rate, of course, the same encoding method is easier to distinguish.

Supplement: vob is the original file format of the DVD, that is, it is not heavily encoded. Of course, it is much larger, and the proportion of the encoded MKV and AVI files is also cleared. MKV and Avi are just a file format encapsulated after the original part is reencoded, because you have not figured out this, so there will be so many problems with these different formats, these problems do not exist after the problem is clarified. The reason why x264 encoding is very popular now is that it can compress the source image into a much smaller file, but the quality of the image can be very close to that of the source image. Earlier DivX encoding is also the reason, but the x264 encoding is better. (The above answers are converted to beater7)

　　Summary:

The video Encapsulation Format is actually a molded file type for the playback service, but it is not a decisive factor that affects the quality of the video.