Research On Hardware Acceleration And Aynchronization Control Strategy For HDTV Stream

With the rapid development of mobile Internet,the streaming media technology,which is applied in digital TV,has been promoted increasingly.The individualized and diversified demand makes mobile digital TV become the development trend of TV terminals industry.The premise of implementing mobile digital TV is to employ a fully functional and high code efficiency Android multimedia service which supports HDTV stream.On the one hand,the number of multimedia format supported by Android multimedia framework has been decreased after OpenCore turns into StageFright.Fortunately,StageFright retains OpenMax IL engine in OpenCore through which DSP is called to realize the hardware decoding in order to improve decoding efficiency.On the other hand,FFmpeg is a famous open source project that includes rich audio and video codec libraries,parser libraries and composer libraries.However,FFmpeg only provides the soft decoding,which is less efficient in HD digital TV decoding,as the high compression rate and Complex decoding operation of HD digital TV consume a lot of CPU.The main work of this paper is that adds the Android multimedia support for digital TV streaming,and realizes the hardware acceleration by the OpenMax calling the underlying decoding chip.This paper focuses on hardware acceleration and synchronization control strategy for HDTV stream,the main research work is as follows:Firstly,this paper presents an architecture model for hardware acceleration applied in HD digital TV.OpenMax is served as a plugin into FFmpeg multimedia framework to conduct hardware decoding,thus to extend the supported format and improve the low decoding efficiency.Secondly,for the interaction between FFmpeg and OpenMax,the framework is designed,communication model between FFmpeg and OpenMax is established and business processes are related.Thirdly,encapsulation interface in JNI layer is designed to provide a common hardware decoding multimedia service.Furthermore,on the basis of the above proposed architecture model,an Event trigger synchronization control strategy is proposed to ensure sync for audio and video.Analyzes the principle of PCR synchronization control method which commonly used in digital TV stream synchronization,pointed out the shortcomings of the method.An Event trigger synchronization control strategy proposed is major for appling to our model,this method is used to control the video playback by the time r when audio played fluently.When audio and video is not sync during playback,the speed of video playback is controlled by adjusting the delay of timer.Finally,experimental platform is built to test the above-mentioned methods.Three different resolutions of TS stream is chosen as the test object.Comparative analysis on the performance of the hard and soft decoding is made through four indicators which are CPU usage,memory footprint,frame rate and decoding time of each frame.Based on event trigger synchronization control strategy,four group of time tag data is extracted to verify the correctness and validity of clock synchronization.