Video compression six standard classification analysis

<br> <br> video compression standard digital video technology is widely used in communications, computer, television broadcasting and other areas, bringing video conferencing, video telephony and digital television, media storage and a series of applications, prompting a lot of video encoding The production of standards. The differences and links between the various compression standards are described in detail below.

1, MJPEG (rarely used)

MJPEG: MJPEG refers to Motion JPEG, which is Motion JPEG, and uses a JPEG algorithm to compress video signals at a speed of 25 frames per second to complete dynamic video compression. MJPEG is developed by the JPEG expert group. The image format is compressed for each frame, usually achieving a compression ratio of 6:1, but this ratio is still relatively insufficient.

The advantage of MJPEG is that the picture quality is still relatively clear. The disadvantage is that the compression rate is low and the bandwidth is large. In general, a single channel occupies a bandwidth of about 2M.

In addition, since MJPEG is not a standardized format, each manufacturer has its own version of MJPEG, and the documents on both sides cannot be identified with each other.

2, MPEG-1

MPEG-1 was once the main compression standard of VCD, and it is also the video compression format widely used by the first generation DVR.

Developed in 1992, MPEG-1 is designed for industrial-grade standards and can be applied to devices with different bandwidths, such as CD-ROM, Video-CD.

MPEG-1 is used to transmit 1.5Mbps data transfer rate of digital storage media moving images and its accompanying sound encoding, after MPEG-1 standard compression, video data compression ratio of 1/100 to 1/200, video image resolution 360×240×30 (NTSC system) or 360×288×25 (PAL system).

3, MPEG-2

MPEG-2 is the designated standard for DVDs. It was established in 1994. The design goal is the picture quality of higher-level industry standards and higher transmission rates.

MPEG-2 is mainly for the needs of high-definition television (HDTV), the transmission rate is between 3-10Mbits/sec, compatible with MPEG-1, suitable for 1.5-60Mbps or even higher coding range. The resolution is 720×480×30 (NTSC system) or 720×576×25 (PAL system).

The picture quality of MPEG-2 is the best, but at the same time, the occupied bandwidth is also very large. Between 4M and 15M, it is not suitable for long-term storage and network transmission.

4, MPEG-4

The MPEG-4 video compression standard was finalized in October 1998 and became an international standard in January 1999.

MPEG-4 is a compression standard for ultra low bit-rate moving images and languages. It combines the advantages of MPEG-1 and MPEG-4. Its transmission rate requirement is relatively low, between 4800 and 64000bits/sec, the resolution is 176X144.

MPEG-4 uses a very narrow bandwidth, compresses and transmits data through frame reconstruction techniques to obtain the best image quality with the least amount of data. The occupied bandwidth of the MPEG-4 standard is adjustable, and the occupied bandwidth is directly proportional to the sharpness of the image.

5, H.263

H.263 is a standard draft of the ITU-T ITU-T. It is a low-rate image compression standard designed for medium-high quality video compression.

The H.263 standard has a high compression ratio. In the full real-time mode of the CIF format, the occupied bandwidth of a single channel is generally about several hundred. The specific occupied bandwidth varies depending on the amount of motion of the picture. The disadvantage is that the picture quality is relatively poor, and the occupied bandwidth greatly varies with the complexity of the picture motion.

6, H.264

The H.264 standard is a digital video coding standard proposed by Joint Video Team (JVT) jointly formed by ITU-T's VCEG (Video Encoding Experts Group) and ISO/IEC's MPEG (Moving Picture Experts Group). It is both ITU-T T's H.264 is also part 10 of the ISO/IEC MPEG-4 standard (also known as AVC, ie "Advanced Video Coding" or "Advanced Video Coding").

Under the same picture quality, H.264 saves about 50% bit rate than H.263, and saves an average of 64% of the transmission bit rate compared with the previous generation encoding standard MPEG2. Compared with MPEG4 (ASP), H.264 saves an average of 39% of the transmission bit rate. flow.

Because of its higher compression ratio, better IP and adaptability of wireless network channels, it has been increasingly used in digital video communication and storage. It should also be noted that the cost of H.264's superior performance is increased computational complexity. It is estimated that the computational complexity of coding is approximately three times that of H.263, and the decoding complexity is approximately twice that of H.263.

The H.264 standard is divided into three profiles: Baseline, Main, and High, which represent algorithm sets and technical limitations for different applications.

Baseline profile: A simple version of H.264, which contains technical features such as low complexity, low latency, and fault-tolerant lines, and is primarily intended for interactive applications.

Mainprofile: The main framework of H.264 adopts several technical measures to improve image quality and increase compression ratio, which can be used for SDTV, HDTV, and DVD.

Highprofile: Mainly for streaming media applications, all fault-tolerance technologies and flexible access and switching technologies for bitstreams are included in this framework.

At present, the domestic industry commonly referred to as MPEG-4 refers to the second part of MPEG-4 (ISO14496-2, also known as SP/ASP), including 3ivx, DivX4/ProjectMayo, DivX5, Envivio, ffmpeg/ffds, mpegable, NeroDigital, QuickTime, Sorenson, XviD and other common video formats.

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