Research Of Solution For ADPCM Encoder On ADSP-BF561

In many stream media applications, the audio is often interlaced with video in the processing of encoding, transmitting, and decoding. Usually, such applications run on the DSP chips whose hardware resource is limited comparatively.In order to realize the video/audio encoder of high performance, based on the processing capacity of ADSP-BF561, the feasibility to run the ADPCM audio encoder using the remainder resource under the condition that more than 98% resource is impropriated by video encoder is analysed. The optimization of ADPCM algorithm and the intergration scheme are analysed. Considering the characteristic that the DSP chip consists of two CPUs and the specialty of video encoder, the audio encoder is implemented on the core whose cost for video encoder is lighter. In this way, not only the cost for communication between the two cores is reduced but also the hardware is enough for audio encoder.The audio/video encoder is required a high quality. Besides, the audio and video should parallel to guarantee the audio and video can be played synchronously. The interrupt mechanism of is analyzed and the interrupt and callback mechanisms are used to realize the parallel processing of ADPCM and H.264 on ADSP-BF561. Considering the specialties of audio data, we storage it before it is encoded. As for the priorities of the input of audio and video, the priority of audio input is set to be higher than that of video to guarantee the timely storage of audio data. According to the delay of audio encoder and the design scheme, the length of audio packet and the number of audio buffers are designed. In order to lessen the influence to video encoder, optimizations are done to speed the processing of audio data.Finally, the parallel encoders are tested. The audio encoder can encode the audio data in real-time with an output of a 32kbps audio stream; The audio buffers are not overflow; the delay of audio satisfy the requirement of system, and there is no dither. It's important to note that the audio encoder just influences the video encoder lightly.