There are two types of digital video recording formats: uncompressed and compressed. D1, D2, D3, D5 and other series of uncompressed recording format, it directly records the input signal at the original signal code rate, maintaining the original level of the signal, and is a lossless recording. The recording method is divided into digital components (D1, D5) and digital composite (D2, D3), which represent the highest standards of video equipment, the highest image quality, and the smallest signal loss, but at the same time due to the large amount of image signal data, the The requirements are extremely demanding, and the price is very expensive. Although the product has been available for several years, only a few video production companies with extremely high image quality requirements use it. The compression format refers to the video using digital compression technology. Common ones include DV, MPEG-2, M-JPEG, etc., and formulate various data compression standards, so the corresponding digital Betacam (DVW), DV, DVCPRO, DIGITAL appear -S, DVCAM, Betacam-SX and other digital video recorders, they compress the image signal and record it on the tape, the purpose is to reduce the amount of image signal data, reduce the size of the equipment, reduce Tape usage achieves the best possible results with minimal signal loss, thereby reducing equipment costs.
1. International standards for digital video technology
(1) Recommendation CCIR601
In order to facilitate international exchange of programs and eliminate the differences in standards between digital devices, making 625-line television systems compatible with 525-line television systems, the International Radio Consultative Committee (CCIR), February 1982, is now ITU Radio At the 15th Plenary Session of the Ministry of Communications (ITU-R), Recommendation 601 was adopted, which was determined to be based on component coding: based on the luminance component Y and the two color difference components RY, BY, as the digital encoding of TV studios International standards.
(2) H.261 standard
H.261 is abbreviated as p & TImes; 64. The standard is used for video telephony and video conferencing. The image coding algorithm is processed in real time, and the delay time is minimum, so that the image and voice are closely matched to achieve full-color real-time motion video transmission and obtain a high compression ratio. The standard was adopted by the International Telegraph and Telephone Advisory Committee (CCITT) in 1990.
(3) JPEG standard
The still image data compression standard JPEG (JointPhotographicExpertsGroup), that is, the Joint Imaging Experts Group, is an international standard organization (ISO), the International Telegraph and Telephone Advisory Committee (CCITT) and the International Electrotechnical Commission (IEC). by. JPEG is both an ISO standard and a CCITT recommended standard. Its goal is to compress still color picture data, which is mostly used for the transmission and storage of satellites and news pictures, as well as graphics and image documentation.
(4) MPEG standard
With the widespread application of digital audio and digital video technologies, the Moving Picture Expert Group of ISO (Moving Picture Expert Group) proposed a draft proposal for the ISOll172 standard in November 1991, commonly known as the MPEG-1 standard, which was adopted in November 1992. The MPEG-1 standard is suitable for application environments with a digital rate of about 1.5 Mbps, which is formulated for video storage and playback of CD-ROM discs.
MPEG-2 is the second standard developed by MPEG and was officially determined as an international standard in November 1994. MPEG-2 is the "Generic Coding of Moving Pictures Associated Audio Informa TIon" standard. As a recognized compression scheme, the standard has the advantages of openness, low technical cost, interoperability and flexibility, optional scalability of bit rate, and support from many manufacturers. It is adopted in the fields of network, communication, satellite, etc. .
MPEG-4 was formulated in 1993 and was not finalized until October 1998. It became an international standard until early 2000. The standard has many compelling features, including video object access based on object content, scalability based on scene content, video access, and error correction capabilities. The MPEG-4 video standard can not only provide a new compression information standard with more compression efficiency, but also has good interactivity and comprehensive storage and endurance. The name is 1 + 2 + 4 = 7 (MPEG-1, MPEG-2, MPEG-4). It expands the limited capabilities of existing dedicated content recognition solutions and includes more data types. MPEG-7 is a standard set of descriptors used to describe various types of multimedia information.
2. Digital video compression method
Based on the above standards, the three compression methods currently widely used in the television field are MPEG-2, M-JPEG and DV. They are all based on discrete cosine transform (DCT), and run-length coding after minimizing the transform coefficients.
(1) Introduction to JPEG JPEG is used for continuously changing still images, including continuous changes in grayscale and color. JPEG contains two basic compression methods: the first is lossy compression, which is based on DCT (DiscreteCosineTransform) compression method; the second is lossless compression, also known as predictive compression method. The former is the most commonly used, that is, the DCT compression method, also known as the baseline sequential codec (BaselineSequenTIalCodec) method. This method is advanced, effective, simple, and easy to communicate, so it is widely used.
(2) Introduction to M-JPEG
M-JPEG is to compress each frame at 25 frames per second at the normal speed required for moving images. Each frame is treated as an independent signal, and its series of frames is actually a JPEG signal flow. The advantage of this design is that it is easy to edit and can randomly edit any frame, which is an excellent choice for nonlinear editing applications. M-JPEG compression and decompression are symmetrical and can be implemented by the same hardware and software. The disadvantage is that it requires too much bandwidth and storage space, because it does not compress the line, but only intra-frame compression, the compression efficiency is not high enough.
(3) Introduction to DV
The DV compression method is an extensible format designed for home video recorders and can be applied to standard-definition televisions and high-definition televisions. DV compression was first developed by an alliance of standard and high-definition home VCR manufacturers. DV uses a 13.5MHz sampling rate, 4: 1: 1 encoding, and 8-bit code to improve the signal-to-noise ratio, and its spatial compression ratio is 5: 1. DV expands from the standard 25Mb / s to 50Mb / s in DVCPRO50 by advocating this compression for substantially inactive video images. Sony provides DVCAM series VTR based on DV compression. There are two main models of DVCPR0 cameras for broadcast television: one is DVCPR025, and the other is DVCPR050.
(4) Introduction to MPEG
The basic steps of MPEG standard digital compression are: first convert analog video to digital video and then group them according to time sequence. Each group of pictures (GOP) selects a reference image, and uses motion estimation to reduce the time redundancy between the images. Perform discrete cosine transform (DCT), coefficient quantization and entropy coding (VLC & RLC) with motion estimation error to eliminate spatial redundancy. The initial tasks of the MPEG expert group are three: to achieve 1.5Mb / s, 10Mb / s, 40Mb / s compression coding standards, namely MPEG-1, MPEG-2, MPEG-3, of which MPEG-3 was cancelled in 1992 .
The MPEG-1 standard is used for moving image and audio coding standards, focusing on high compression ratio, with low bandwidth and low resolution, and the video rate is roughly 1.5Mb / s. The basic algorithm is to compress the spatial resolution in the horizontal direction (360 pixels) and vertical direction (288 pixels), and it has a relatively good effect on moving images with 24 to 30 frames per second. The MPEG-1 standard also provides some VCR functions: forward playback, image freeze, fast forward, fast reverse, and slow playback, as well as random storage functions. The MPEG-l standard also uses a series of techniques to obtain high compression ratios: ①Sub-sampling the color difference signal to reduce the amount of data; ② Using motion compensation technology to reduce the line quantization, discarding the unimportant information, and quantizing the DCT component Reordered according to frequency; ⑤ The variable word length coding of the DCT component; ⑥ Predictive differential coding of the DC component (DC) of each data block.
The MPEG-2 standard is similar to the MPEG-1 standard, and its bit rate is much higher than the latter, which requires higher bandwidth and resolution. The MPEG-2 standard can define a bit rate of up to 400Gb / s and an image of 16000 & TImes; 16000 pixels. It uses intra-frame coding and quality sword-GOP (group of pictures) is divided into I frame (intra-frame coding frame), P frame (forward prediction coding frame), B frame (bidirectional prediction frame), take different Compression coding method. In January 1996, the International Munich Group Meeting confirmed the MPEG-2MP @ ML standard with high broadcast quality and high editing accuracy, which allows shorter GOPs, making it suitable for precise editing of program production. MPEG-2 can automatically change the compression ratio in the "simple" and "complex" areas of the image. It can use different compression ratios in the same frame, so it is more effective. Under the condition of compression to the same image quality, the space occupied by MPEG-2 images is only 10% to 15% of that of M-JPEG images. In various fields such as image acquisition, production, transmission, broadcast, etc., MPEG-2 has gradually been widely adopted.
In addition to fully supporting all the video functions provided by MPEG-1 / 2, MPEG-4 includes effective encoding of standard rectangular area image sequences under different input formats, frame rates, and bit rates, and also adds new functions: Transmission efficiency, MPEG-4 uses "sub-picture" prediction and coding technology, it uses the static background as "sub-picture", first sent to the receiver, as the first frame is stored in the encoder and decoder, and then use the camera Moving, rotating and zooming, capturing video objects that appear in front of the background, and then encoding them separately, forming a video sequence for transmission, and then reconstructing the original image. This technology is very beneficial for the realization of multimedia databases, while also improving image quality. MPEG-4 is a high-efficiency coding standard, and its minimum bit rate can reach 5 ~ 64kbps. For specific videos, their interactivity and operability are compatible with various encodings in the field of multimedia applications. MPEG-7 is based on MPEG-4, and retrieves information content with few features. For example, for graphics, as long as a few lines are drawn, you can find the corresponding graphics, trademarks, etc. that include this feature.
3. Comparison of 3 common digital compression formats
M-JPEG, DV, and MPEG are the three main compression technologies in the video industry. They are all based on DCT, and the images they record are converted into frequency domain coefficients that are unified, quantized, and variable-length encoded. The digital video coding technology commonly used in broadcasting and TV. Among them, DV and typical M-JPEG are intra-frame coding, which uses intra-frame compression mode, without suffocation. For MPEG-2, when using> Kyu? MPEG-2 is used for editing, it is generally limited to I-frame encoding, and can switch frames at the edge without knowing the previous frame and the next frame. In addition, DV and MPEG-2 compression use motion adaptive processing to achieve effective intra-frame encoding, but DV can only perform fixed bit rate (CBR) encoding, while MPEG-2 and M-JPEG can perform CBR and variable Bit rate (VBR) encoding.
Digital video compression technology enables us to obtain high-quality video at a lower cost, making it possible to spread video signals for high quality, and with the continuous development of TV technology, this technology is constantly updated and improved. When TV technology and Internet technology are combined, digital video technology more reflects the advantages of communication and communication.
Mainly used for Solar power storage system, home solar system, this kind of battery has more than 2500 cycle life.
LFPS series lithium battery using LiFePO4 Battery cells with more advantages as following:
â—† Longer life compare to Lead Acid Battery
â—† Up to 60% weight saving
â—† 100% usable capacity
â—† More energy with 1/3 smaller size
â—† Less than 3% self discharging
â—† Built in safety protection
â—† Zero maintenance
â—† Easy installation
â—† Eco-friendly
â—† Quality guaranteed
LiFePO4 Solar Energy Storage Batteries
Solar Power Battery,Portable Solar Power Battery,Lihtium Solar Power Batteries,Solar Power Deep Cycle Battery
Starlight Power Industrial Company Limited , https://www.starlite-power.com