| Nowadays, along with the development of science and technology, Technology of communication and Internet have developed in high speed. People depend on technology and hope that technology can bring more and more convenience to them. So smart-phone has been realised. Because of development of 3G, the development of smart-phone must satisfy people's requirement(ringing,web,email,navigation,browsing information,video TV that handset is used as playing media and monitoring and so on), thus smart-phone will play a leading role in the trade of handset. This field may have enormous trade prospect.Because people have need of stream-media information by using handsets and immediacy that handsets running applications higher, so it is necessary that handsets must have function that handsets can handle more clear stream-media files.Porting and optimizing the advanced H.264 decoder in smartphone is the key technology in the realizing of mobile video application.This article carries out the porting and optimizing method in algorism and code two ways.Aiming at the demand of H.264 application in Android platform,the paper carries out research and development on H.264, the work I have done is as following:(1) Firstly, the paper analyses the present research situation on smartphone and H.264, analyses and compares some different smartphone systems.The paper has done detailed description on the architecture of Android.Simple analyse has been done aimed at the embedded development system and how to build exploit environment.(2) The paper analyses some main modules including the actual process of intra prediction and inter prediction mode,technical principles and processes of DCT and the linkages and differences between various profiles.Optimizing key algorithms is for enhancing the performance of H.264 decoder.(3) Definition of the interface for target board jz4750 about Opencore have been done. during reading and writting data of multimedia, it is necessary to operate the data in the storage device, how to improve the speed of reading and writing of data is important, as NANDFLASH is mainly used as data storage device in the paper, so I put forward optimization and design concerning the driver of NANDFLASH in process of reading and writting data.(4) At last,aiming at some limition(restricted resources,small memory,the complexity on operating float and so on) in exploiting,the paper also optimizes according with hardware and code. In the paper, I transplant FFmpeg to Android. because it is only the necessary to support data of H.264, so we should cut off some functions that I don't need,we can save some system resources.In the end,the paper realizes the decoder porting in Android platform and shows the result. |
