1) MJPEG
MAPEG refers to Motion JPEG, ie dynamic JPEG, compresses the video signal with a JPEG algorithm in 25 frames / sec, completes the compression of dynamic video. It is made by the JPEG expert group, and its image format is compressed for each frame, typically 6: 1 compression ratio, but this ratio is still not enough. Just like each frame is an independent image. The unit of the MJPEG image stream is a frame of one frame of JPEG. Because each frame can be accessed, MJPEG is often used for video editing systems. Dynamic JPEG can produce high quality, full screen, full-moving video, but it needs to rely on additional hardware. Moreover, since MJPEG is not a standardized format, each manufacturer has its own version of MJPEG, and the documents of both parties cannot identify each other.
The advantage of MJPEG is that the quality is clear, the disadvantage is that the compression ratio is low, and the occupied bandwidth is very large. General single occupied bandwidth of about 2m.
2) H.263
The H.263 video coding standard is a low yard ratio image compression standard designed for medium and high quality motion image compression. H.263 uses a common coding method in motion video coding, divided the encoding process into two portions of intra coding and inter-frame encoding. Inframe uses improved DCT transform and quantizes, using 1/2 pixel motion vector predictive compensation technique, so that the motion compensation is more accurate and quantified, and the improved variable length coding table (VLC) is quantified to entropy encoding. , Get the final encoding coefficient.
H.263 Standard compression ratio, CIF format all-on-time mode is generally about a few hundred, and the specific occupancy bandwidth view is different. The disadvantage is that the quality is relatively different, and the occupation of the bandwidth with the complexity of the picture movement.
3) MPEG-1
VCD standard.
Developed in 1992, designed for industrial grade standards, applicable to different bandwidth equipment, such as CD-ROM, VIDEO-CD, CD-I. It is used to transmit a digital storage medium of 1.5Mbps data transmission rate and the encoding of its sound, after the MPEG-1 standard is compressed, the video data compression ratio is 1/100 ~ 1/200, the resolution of the film and television image is 360 × 240 × 30 (NTSC system) or 360 × 288 × 25 (PAL system), its quality is slightly higher than the quality of the household video system (VHS-VIDEO HOME SYSTEM). The audio compression ratio is 1 / 6.5, and the sound is close to the quality of CD-DA. MPEG-1 allows for more than 70 minutes of high quality video and audio stored on a CD-ROM disk. The VCD is the standard of MPEG-1, which is a video, audio compression standard for home TV quality. The MPEG-1 coding rate is up to 4-5 Mbits / sec, but as the rate is improved, its decoded image quality is lowered. MPEG-1 is also used on video transmission on digital telephone networks, such as non-symmetrical digital user lines (ADSLs, video on demand (VOD), and educational networks. At the same time, MPEG-1 can also be used to transmit audio on the Internet or on the Internet. The network bandwidth of the MPEG1 standard is about 1.5m.
4) MPEG-2
DVD standard.
Developed in 1994, the design goal is the image quality of the advanced industrial standard and higher transmission rate, mainly for high-definition television (HDTV) needs, with MPEG-1 compatible with MPEG-1, with MPEG-1, compatible with MPEG-1, and MPEG-1 is compatible with MPEG-1 compatible with MPEG-1 compatible with MPEG-1 compatible with MPEG-1 compatible with MPEG-1 compatible with MPEG-1 compatible with high-definition television (HDTV). Suitable for 1.5 to 60 Mbps or even higher coding ranges. The resolution is 720 × 480 × 30 (NTSC system) or 720 × 576 × 25 (PAL system). The quality of the film and television image is the quality of the broadcast level, and the sound is also close to the quality of CD-DA. MPEG-2 is twice the resolution of a household video system (VHS) tape. The audio coding of MPEG-2 can be provided with two surround channels, as well as an aggravated bass channel, and up to 7 parties (DVD can have 8 language dubbing reasons). Since MPEG-2 is ingenious during design, most MPEG-2 decoders can also play data in MPEG-1 format, such as VCD. In addition to the designated standards for DVD, MPEG-2 can also be used to provide broadcast, cable TV, cable network, and multi-level live broadcast (Direct Broadcast Satellite). Another feature of MPEG-2 is that it can provide a wide range of variable compression ratios to accommodate different picture quality, storage capacity, and bandwidth requirements. For end users, due to existing TV resolution restrictions, the high-definition screen quality (such as DVD screen) is not obvious on TV, and it is its audio characteristic (such as aggravating bass, more Sound channel, etc.) more compelling. The quality of the MPEG-2 is preferably, but it also has a very large bandwidth, between 4M to 15M, is not suitable for remote transmission.
5) MPEG-4
If the MPEG-1 "file is small, but the quality is poor"; and the MPEG-2 "good quality, but more space", then MPEG-4 combines the advantages of the top two. It was finalized in October 1998 that became an international standard in January 1999, followed by the development of the second edition for extended purposes, ending at the end of 1999. MPEG-4 is a compression standard for ultra-low yield motion images and languages, but it is not only for video, audio coding, but also more attention to the interactivity and flexibility of multimedia systems. MPEG-4 standards are mainly used in Video Phone, Video Email and Electronic News (Electronic News), and its transmission rate requires low, between 4800-64KBITS / SEC, resolution It is 176x144. MPEG-4 utilizes a very narrow bandwidth, with frame reconstruction technology, compression, and transfer data to obtain optimal image quality with least data. MPEG-4 provides a broader platform for multimedia data compression than MPEG-1 and MPEG-2. It is more defined in a format, an architecture, not a specific algorithm. It can fully use a variety of multimedia technologies, including some tools, algorithms that compress themselves, algorithms, including image synthesis, speech synthesis, and other technologies. MPEG-4 features that it is more suitable for interactive AV services and remote monitoring. MPEG-4 is the first dynamic image standard that makes you passively become active (no longer just viewing, allowing you to add interactive); another feature of its comprehensive; from the root MPEG-4 attempts to dissolve natural objects with artificial objects (visual effects). MPEG-4 design goals have wider adaptability and scalability.
The occupied bandwidth of the MPEG4 standard is adjustable, and the occupied bandwidth is proportional to the sharpness of the image. With the current technology, generally occupy the bandwidth of about hundreds k.
