Design And Implementaion Of Embedded Audio Player System

The embedded system is a computer system which is oriented to application, based on computer technology, and can be configured in software and hardware. The embedded system is usually composed by four different parts, the embedded microprocessor, the hardware device, the embedded operating system and the application program. It is used for controlling, surveying and managing other devices. This paper describes the finish of the audio playing solution on a embedded platform. On the basis of a SoC with core of ARM9, this paper gives the software structure above the hardware, which includes the bottom device driver, the mesosphere task management and the application program. And this paper gives the optimization method of decoding program.First, in this paper, the device registration is implemented using the linking script, and all the devices are managed through the device structure registration. Any call of device function from the application should use the registered device structure. This paper gives a task management system design and designs task management structure which includes the initial recourse, running functions, private resource and the task in and out disposal, and all the task structure is under the administration of the task chain, different chain means different task status, so the task status switching in fact need transfer the task structure to corresponding chain. In this paper, the management of different type memory depends on independent memory pools, inside the memory pool, the memory allocation method is the next fit method.In this paper we analyze the character of hardware and then design the multi buffer audio driver according to the hardware. The multi buffers get the data from the caller of driver and then put the data out, different buffers are connected by the interrupt when one buffer finished. For the noise from hardware, This paper gives the software solution of empty buffer, that is when the hardware initialized, we first transfer zero data, thus the voltage to hardware can be stable, and the noise is diminished.The decoding program is the application of audio playing, this paper transplant the open source code to our task management to complete the MP3 decoding, and optimize the performance of decoding. The optimization concerns to two aspects. First according to the embedded hardware, we accelerate the read and write speed of key data in MP3 decoding. Second, we use the ARM9 multiply-accumulation instruction to optimize the code which focuses on add and multiply computing, and replace the original c code with assembly code. Thus, with the software platform implemented above, on the comparison of audio playing, the decoding performance after optimization has a significant improvement.