There is a wireless video transmission technology in the multimedia conference room system. This technology is realized by a wireless touch screen, that is, a video signal is displayed on the wireless control terminal, so that the wireless touch screen not only has the function of the control platform, but also can display the monitoring screen. The touch screen is more fashionable.
Wireless video transmission technology seems simple, but there are great difficulties, especially in touch screens. The wireless channel has limited bandwidth resources and many interference factors, while the video signal has a large amount of data and high real-time requirements. Therefore, research on wireless video transmission technology has attracted wide interest from scholars at home and abroad. The main difficulties in implementing wireless video transmission technology in the touch screen are: video compression coding technology and video coding real-time technology, as well as code rate control to ensure the stability and high fidelity of the video picture.
1, video compression coding technology
The amount of video information is so amazing that it must be compressed and encoded on a wireless network with limited bandwidth. At present, there are two major standardization organizations in the world - ITU-T and MPEG - specializing in video coding methods, responsible for the standard of fairness and uniformity, and facilitating the interoperability between various video products. These agreements focus on the best results in academia. In addition to a variety of coding techniques based on international standards, the development of many new technologies is compelling.
2, video coding real-time research
Due to the particularity of video data, video transmission systems are highly demanding in real time. The focus here is on the real-time problem based on the video coding protocol algorithm. Although wavelet coding and other algorithms have many advantages, the complexity of the algorithm is too high, and it is difficult to achieve real-time requirements at present. The following describes several important aspects of the protocol-based coding algorithm, which play an important role in improving the real-time performance of the video coding system.
3. Research on code rate control
The coding strategy is an important part of the encoder. Rate control technology is one of the key technologies in video communication applications. It is responsible for the coordination between the various links of the encoder and the transmission channel and decoder, and plays an important role in the encoder. Since the rate control strategy needs to be determined by the specific application, video coding protocols such as H.263+ and MPEG-4 do not specify a specific rate control method.
Because the video stream structure has the characteristics of layering, the research of the rate control scheme is generally divided into two layers, namely image layer rate control and macroblock layer rate control. The main task of the image layer rate control is to determine the output expectation of the frame image before encoding the image frame according to the expectation of the encoder output rate, the limitation of the system transmission delay, and the overflow of the transmission buffer. The number of bits; the main task of macroblock layer rate control is to control the number of expected bits of the frame image determined according to the image layer rate control, and select an appropriate quantization step size for each part of the image. The main basis for macroblock layer rate control is the Rate-DistorTIon model.
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