Analysis of various multimedia formats and Codec

First, we need to understand several concepts:
A. scanning line and resolution
The scanning line can be understood as dividing the horizontal direction of the screen into lines, just like a horizontal line forming a plane. The screen definition basically depends on the smoothness of the scanning line. In other words, the scanning line determines the physical resolution of the screen. The physical resolution refers to the maximum number of pixels displayed on the screen. Physical resolution determines the maximum resolution that the screen can achieve. In addition to the maximum resolution of the screen, there is also a concept of compatible resolution, for example, A 640*480 screen may also play signals in the 1080*720 format and compress the signals to the display range. In summary, the scanning line determines the definition and resolution. The following lists several common scanning formats:

1. D1 is in the 480i format and has the same definition as NTSC analog TV. It has 525 vertical scanning lines, 483 visible vertical scanning lines, 4: 3 or 16: 9, line/60Hz, and line frequency of 15.25 kHz.
2. D2 is in the 480p format. It is the same as a row-by-row scanned DVD. It has 525 vertical scanning lines and 480 visible vertical scanning lines. The resolution is 640 × 480 at or, line-by-line/60Hz with a row frequency of 31.5 kHz.
3. D3 is in 1080i format. It is a standard digital TV display mode, with 1125 vertical scanning lines, 1080 visible vertical scanning lines, resolution 1920 × 1080, and line separation/60Hz, the frequency is 33.75 kHz.
4. D4 is in the 750 p format. It is a standard digital TV display mode with 720 vertical scanning lines and 1280 visible vertical scanning lines. The resolution is 720 ×, row-by-row/60Hz, the line frequency is 45 kHz.
5. D5 is in the 1080p format. It is a standard digital TV display mode, with 1125 vertical scanning lines, 1080 visible vertical scanning lines, and a resolution of 1920x1080 lines. It is in professional format.
6. In addition, there is 576i, which is a standard pal TV display mode. There are 625 vertical scanning lines, 576 visible vertical scanning lines, or 16: 9, separated lines/50Hz, recorded as 576i or 625i.
 
In the above standard, "I" indicates the line separation, and "p" indicates the line by line. The HDTV standard is a high-quality video signal standard, including 1080i, 720 p, and 1080 p. That is to say, D3, D4, and D5 belong to the HDTV standard, but currently P is supported. It should be noted that the requirement for TV processing capabilities (such as bandwidth) is 480 I <720 p <1080i <p. So currently, few TVs that support P of chromatic aberration input, but many of them support 1080i or 1080i ready.
The 720 p, 1080i, and 1080p formats of Digital HDTV are standard HD formats determined by the motion picture and Television Engineers Association of America. 1080p is currently called the top-level display format of Digital TVs, in this format, TVs can scan 1920x1080 in a row-by-row manner. At present, only over 60 inch Of the world's display screens can display signals of 1920x1080. Currently, the so-called 1920 p high-definition digital TVs on the market cannot bring 1080x1920 images to consumers. These TV sets can only receive and process signals in the 1080 x format, currently, TV signals cannot meet such a high standard. Therefore, 1080p has little practical value for common users.

B. Multimedia container format
The multimedia container format is like the multi-media format we use. MP4 ,. 3GP ,. avi ,. ASF and so on are all multimedia container formats. They contain multiple encoding formats of video and audio. In multimedia, MUX and Demux are used to mix audio and video data (MUX) in the file format) and Demux In the decoding process ). Let's take a look at several container formats:

1. MP4
A multimedia container format defined by the MPEG-4 [MPEG-4 part14], widely used to store audio and video streams, as well as static images and subtitles. You can basically store the vast majority of data that can be embedded into MP4:
Video: MPEG-4 Part 10 (or H.264, also known as MPEG-4 AVC), MPEG-4 part 2, MPEG-2, and MPEG-1.
Audio: MPEG-2 Part 7 (also known as AAC), Apple lossless, MPEG-1 audio Layer 3 (also known as MP3), MPEG-4 part 3, MPEG-1 audio layer II (also known as MP2), MPEG-1 audio layer I, CELP (speech), twinvq (very low bitrates), saol (MIDI ).
Subtitles: MPEG-4 timed text (also known as 3GPP timed text ).

2. 3GP
3GP is a multimedia container format mainly used on mobile devices by 3GPP, with the extension. 3GP is generally used on GSM ,. 3g2 is generally used in CDMA, 3GP is actually very similar to MP4, both are based on MPEG4-part12. The media stream carried by 3GPP is generally:
Video: MPEG4-part2/h263 MPEG4-part10/h264
Audio: AAC AMR-NB AMR-WB

3. MKV
Matroska multimedia container is a fully open-source multimedia container format that encapsulates videos in multiple encoding formats, audio in up to 16 formats, and Subtitle data in a matroska media file. The goal of MKV is to replace some existing encapsulation formats such as. ASF. Avi, but no one knows what the open-source stuff can accomplish ~~

4. Avi
Avi is a product developed by Microsoft. It is mainly used on multimedia CDs to store TVs and movies. Because it is too large and incompatible with the standard, it will not be used much on mobile phones in the future, I will not talk about it here. If you are interested, you can check it on the Wiki.

In addition to this, there are also a lot of Apple QuickTime, ASF, vob, and so on. We should not use much on our mobile phones, so we will not talk about it here.

Now let's take a look at the various basic coding and decoding methods. Now the mainstream music encoding methods are AAC and MP3. The main human voice encoding methods are AMR and Amr +, and the main types of videos are h263, h264 and MPEG4, except for AMR being 3GPP, are all in the mpeg protocol cluster. In addition, Microsoft's WMA and WMV won't be mentioned.

MPEG (Moving Picture Experts Group) is ISO first proposed for audio and video compression and transmission of a protocol cluster, this protocol cluster should be very large, divided into many versions such as MPEG-1, MPEG-2, MPEG-3, MPEG-4 and so on. Next we will only choose what we may use in the future:

1. MPEG-1 audio Layer 3.
Is our familiar MP3, in fact it is the content of the MPEG-1 protocol, in fact it has gone through the development of MP1, MP2, and finally to MP3, MP3 is a lossy compression format for music.

2. MPEG-4 Part 2: MPEG-4 SP and MPEG-4 ASP
The two are different. SP is mainly used in low-speed scenarios, such as mobile devices, while ASP is actually similar to h263.

3. MPEG-4 Part 3
It is the advanced audio codec that we are not very familiar with. It should be said that AAC will replace MP3 in the future. It supports 96 KHz sampling frequency and 48 channels, as well as a variety of technologies such as SBR, providing high compression and high-quality audio.

4. MPEG-4 Part 2 MPEG-4 Part 10
This is the h263 and h264 (AVC) We should be not very familiar with, in fact, the h26x series of protocols are all later added to the MPEG-4 protocol cluster, because of its high performance compression. Although in the same frame, they are actually not the same video codec as the MPEG-4. It should be said that according to the performance of codec used in different aspects, MPEG-4 is now mainly used in the field of monitoring video encoding. H264 has many versions, including BP, SP, and hip.

Finally, let's talk about the human voice encoding Amr. The human voice encoding is a high compression encoding method, which is completely different from the music encoding algorithm. It should be said that they are basically based on CELP, amr is defined by 3GPP, including narrowband amrnb and amrwb used on broadband.

This article from the csdn blog, reproduced please indicate the source: http://blog.csdn.net/yili_xie/archive/2009/11/12/4803509.aspx