Based on the MPEG-4 video of key technology medical systems

0 introduction

With the emergence of wireless multimedia applications and the reproduction of multiple data services, wireless services are widely applied to various aspects, in multimedia communication using the wireless network to transfer audio and video information becomes more important.

This requires in multimedia information processing to dynamically, real-time processing of sound, animation and video signal, but the computer cannot live from memory the image information processing of mass data transfer to a central processor, therefore if the wrong video data compression, in order to achieve real-time performance requirements is almost impossible. This requires the easy bit error of wireless environment safe low bit-rate encoding and transmission, MPEG-4 technology as this provides the implementation.

MPEG-4 image compression technology for a bit rate of video and audio encoding, stressed the interactivity based on content.

Therefore, use MPEG-4 encoding and decoding technology for video data compression has become a multimedia system development for wireless video transmission of key technologies. Multimedia videoconferencing system is a computer technology and communication technology products, through multimedia and communication technology support to people across the region provides a mutual exchange, discussion questions and cooperative work (CSCW), and "you see is what I see" effect.

Multimedia video conferencing system will greatly enhance people's productivity, and will change the traditional and exchange patterns, far-reaching and profound social significance.

Video medical systems is a multimedia video conference system

Commission of a new application areas.

In the video, medical system from JMF (JavaMedia Framework) provides a unified framework and communication protocols to manage the time-based media acquisition, processing and transmission. Using real-time Transport Protocol/real-time Transport Control Protocol (RTP/RTCP) good guarantees the video in real-time, and introduces the JMF MPEG-4 compression algorithm plug-in for video compression. MPEG-4 compression algorithm of compression ratio is high, and have a good network adaptability. In the program implementation process to good effect.

1 MPEG-4 key technology

MPEG-4 adopted object-based coding technology, the second generation and use the AV (Audio/VisualObject) Visual encoding, while providing many content-based interactive video services, also supports traditional streaming video.

MPEG-4 apart from the first generation of video coding technology (such as motion estimation and compensation, entropy encoding), it also raised a number of new key technologies:

1) MPEG-4 video object segmentation based on the content of interactivity most notably through the video object segmentation.

The so-called video object segmentation, that is, video, image split into different objects or moving objects separate from the background, and thus to the different objects using different encoding method to achieve high compression, such as moving objects using the compression ratio is low, the loss of smaller way, as far as possible, preserve the video object details and smoothness; on the background object using large compression coding strategies, in order to achieve the compression efficiency and decode images better balance. Basic can be divided into three steps: through the filter to the image data is simplified; on the video, images, data extraction, such as color, texture and movement, semantic characteristics; and finally the post-processing actions related to achieve noise and accurately extract boundaries.

Thus, the technical requirements on MPEG-4 encoded image and video make more analysis to understand, but different from the past of the compression algorithm, just remove the intra and inter's redundancy.

Therefore the encoding based on object can improve data compression ratio, video object segmentation (extract) technology has also become a MPEG-4 video coding key technologies.

2) video coding scalable technology video classification coding technology is designed to address the various transmission characteristics of heterogeneous network video transmission needs.

Video encoding of scalability, refers to the bit rate can be adjusted. In other words, video encoding compression only once, but can take multiple frame rate, resolution, or video quality to be decoded, thereby supporting the different users of different application requirements. Video encoded classification technology is through the video object layer (VOL) data structure to achieve. There are two basic grading tools, namely the classification and airspace classification in the time domain, it also supports mixed-domain airspace classification. Each level coding at least two layers of VOL, low level (basic level) used to provide basic information about the video sequence, senior (reinforced layer) use to provide video sequences with a higher resolution and detail.

3) motion estimation and compensation technology in video coding, motion estimation consuming real-time on encoding.

Part of the motion estimation, must by repeated calculations to determine adjacent frames macro module dependency. Usually use block-matching criteria for estimates, such as absolute error and (SAD) and the mean square error (MSE) criteria, to select the best match for an operation to generate the best matches for motion estimation. For example, you can develop MPEG-4 dedicated adaptation then synchronization, data segmentation and data recovery of syntactic units to optimize bit stream, so that it has fixed fault tolerance. In most cases, high compression ratio of the video data cannot be avoided by the channel of the BER degradation. However, just by taking a series of appropriate methods and tools to reduce the impact of the error, high-quality wireless video transmission is possible.

2 MPEG-4 technology — video medical systems

Through the above on MPEG-4 video coding and analysis of key technology, we can see, the MPEG-4 video encoding video transmission has its unique advantages: (1) content-based interactivity;

(2) efficient encoding method; (3) universal accessibility.

The video conference system

Used in medical procedures, medical system of video is a video conference, a new application areas. In the video medical system, you can use the point-to-point or point-to-multipoint application forms to the diagnosis and treatment, as well as one-on-one expert consultation, can also be used for medical practice. Video system with video real-time acquisition, real-time synchronous compression, transmission and playback functionality. In other words the transfer local video, you can play back and monitor local video information, and also provide video snapshots and storage capabilities. Figure 1 is a system architecture model diagram.

　　

　　

You can see from Figure 1, the video medical system, based on the MPEG-4 for video capture and compression are the key steps.

In the design of video health system, since the software's video compression algorithm is very time-consuming, so in order to improve the compression efficiency, introduces the JMF MPEG-4 compression algorithm plug-in, adopted based on the MPEG-4 video acquisition and transmission technology for video compression, while assisting with double buffering and multithreading technology.

Video object interaction and decoding of an important prerequisite is the use of video object segmentation by motion estimation and compensation technology to get an information based on the movement and the Visual characteristics of the track, and the resulting video object tracking results.

In the video capture threads will be collected every frame of video images are kept to a video source buffer 1 and video 2 source buffer, and then through the software compression thread on frequency source buffer 1 and video 2 source buffer image compression, and the compressed results saved to compress the video buffer is 1 and 2 compressed video buffer. In the two video source buffer at least

One is empty, the video capture threads will continue to work for image acquisition; similarly, when the video source buffer at least one is full, and compress video buffer at least one is empty, the software compression thread compression.

All compressed video data thread arranged according to the queue, they can also use a non-empty compressed video buffer data. When the last thread when you are finished using the compressed video buffer, to the video capture thread collection the next command. Remove the data from the buffer and the buffer state blank, to put the data in the buffer when the State of the buffer to the full. And MPEG-4 video coding scalable technology enables video with different transmission characteristics of a heterogeneous network of transmission have been achieved.

MPEG4 compression algorithms for the compression ratio is high, and have a good network adaptability.

In the compression algorithm using MPEG-4 while using double buffering and multithreading technology, you can make the image capture, compression, and transmission executed concurrently, greatly improving efficiency in the use of CPU, video capture, compression, and transmission of the overall performance is greatly improved.

Video capture compression of the flowchart shown in Figure 2.

　　

　　

After video capture image compression gets shown in Figure 3.

　　

　　

3 conclusion

Since the MPEG-4 scalability and flexibility as well as the emergence of broadband wireless network, you can see in the near future wireless multimedia services will become the trend of the times.

Broadband wireless network in the MPEG-4 video transmission will be emerging multimedia applications is an important component. MPEG-4 low storage capacity and high-definition of the characteristics that determine MPEG-4 in low-bandwidth networks become a superior video compression method. It can thus be seen that video medical system video compression, use based on the MPEG-4 compression algorithm plug-in for one-to-one video transmission, you can get better quality video images, and a basic up to the system requirements of real-time performance, this is the traditional multicast video system.