【作者】 王成利；

【导师】 陈贺新；

【作者基本信息】 吉林大学 ， 通信与信息系统， 2005， 硕士

【摘要】 在信息社会,人们迫切希望计算机能以人类习惯的方式提供信息服务,因而多媒体技术应运而生。它的出现,使得原本只有文字界面的计算机有了生动的面孔。人们不仅可以通过直接看到的影像和听到的声音来学习和使用对象,并可以参与或者改变信息的演示。接着,多媒体视频、音频通信也随之出现了,这将是通信的发展方向。本文讨论了面向对象的MPEG-4视频压缩编码算法的整体流程及MPEG-4简单子集(SP)的DSP实现过程,并结合硬件主芯片——ADI公司的Blackfin系列ADSP-BF533的特点,对编码过程中的部分算法模块进行优化。本文最后使用几种标准测试序列对ADSP-BF533实现的编码器进行了测试,并对实验结果分别进行了定性和定量的分析。实验结果验证了编码器的有效性,并且通过硬件仿真说明了基于ADSP-BF533的实时嵌入式视频处理器是可行的。更多还原

【Abstract】 In the past several years, Telecommunication makes progress constantly. With the development of hardware and the increase of frequency bandwidth, video communication plays a more and more important role. Because of the popularization of mobile communication recently, wireless video becomes the mainstream. Facing to extensive and quantity sharply increasing users, their demands can not be satisfied with the increase of bandwidth. Under the condition of limited bandwidth, video compression can make use of bandwidth more effectively, so more quality and more compress ratio video compress standard becomes the focus of the market. Nowadays, there are a lot of video compressing encoder standards. In Part 1 of this paper, we introduce some familiar video compress encoder standards, such as MPEG-1/2/4/7/21 and H.261, H.263, H.264. Among these standards, MPEG-4 is a new video standard based on H.263, MPEG-1 and MPEG-2, it commits itself to realize video compress and communication at different bit rate. Because MPEG-4 is support of MPEG-1 and MPEG-2 and introduce new encode algorithm, compression rate improve by a large margin. And MPEG-4 offers new multimedia service. Multimedia communication will become more vivid, convenient and inter-dynamic. MPEG-4 is a video compress standard based on content, this is its most remarkable character. In this method, a scene is composed of some interesting characteristic video object (VO). We can encode these objects respectively and transmit and decode these objects selectively, or add new object, then create the scene which we are fond of. The video object is an accessible and operable entity in a scene. In an idiographic scene, video object is an interesting region composed of entities. Encoding an object can form an object bit layer. This layer includes shape, position, texture, etc. This “based on content”encode method is very flexible, so MPEG-4 is suitable for low bit rate and interact situation. Another key function of MPEG-4 is expansibility. It includes definition adjustable and objects adjustable character. The former is that the content and the quality of the image can be expanded at accurate interval. The latter means that it can add or delete object in the encoded scenes. When the network bandwidth becomes narrow, we can transmit the video signal by reducing the quality in order to reduce the demand of the bandwidth and guarantee the continuity of video communication. MPEG4-SP is a special simple MPEG-4 model. SP means simple profile. Because its algorithm is simple correspondingly, it is suitable to realize by hardware real-timely. Different from above-mentioned MPEG-4 standard, MPEG4-SP is not a kind of encoding standard based on objects, and it has not multi-object encoding tools at the same time. It encodes the video signal based on rectangle frames. It inherits from H.263, MPEG-1 and MPEG-2 and it has not information of scenes and objects. At present, most MPEG-4 products in the market are all realized in the way of MPEG4-SP. They can not realize the algorithm of based on objects. The algorithm of based on objects indeed is not mature. So people are discussing and studying extensively in this field. MPEG4-SP model inherit the algorithm from MPEG-1 and MPEG-2, enumerate them as followed: IVOP (visual object plane, it is based on rectangle frame): DCT&IDCT; Quantization & Inverse Quantization; (we can select the method of H.263 or MPEG-2) Rebuild the VOP; VLC (Variable Length Code, that means entropy code); P_VOP: Interpolate; ME (Motion Estimation); Half Pixel Interpolate; MC (Motion Compensation);Difference of VOP frames; MPEG4-SP model has its own characters (compared with H.263, MPEG-1 and MPEG-2). Such as followed: In support of the quantization and inverse quantization algorithm of H.263 and MPEG-2; Forecast the DC and AC coefficients of intra-macro-block; Advanced forecasting motion vectors; Unlimited motion estimation and motion compensation; Special Zigzag scanning mode Overlap motion compensation; On application of MPEG4-SP model the encoded data includes two kinds of information. One is texture information, namely the video compressed data; other is motion information, we can comeback the PVOP by using motion information. By applying these algorithms on the MPEG4-SP encoder, we can obtain better compressed results. Considering the realization of video compression standard, the appearance of high performance and universal chip make it possible that we realize video encode by hardware except that we realize the encoder by software. And that the realization on DSP is a quite popular solution in recent years. Its advantages are that the cycle of research and development is short, the chip’s speed can meet the demand of the MPEG-4 encoder, and we also can ameliorate the algorithm according to the demand at any time. Certainly it has a lot of shortcomings, for example, the DSP chip is very expensive. We can not produce a large number of products. But after the appearance of mature DSP, there will be better commercial value. In this paper, we use the product of Analog Device-ADSP-BF533 to realize the MPEG-4 encoder. In part 2, we introduce the core architecture and main peripherals of ADSP-BF533. The algorithm of the encoder is MPEG4-SP, it has mature technology and simple operation. We also can optimize the algorithm module according to the character of ADSP-BF533 and special video pixel更多还原