基於Dual-Core DSP之H.264與AAC影音同步編解碼器之實現

Abstract

本論文提出一個充分利用雙核心特性的H.264與AAC之同步編解碼系統，由於採用資源有限之嵌入式系統開發之故，在演算法的層次上，對於複雜影音的編解碼運算進一步的根據平台加以簡化；在記憶體管理方面，將其使用量降至最小，並且設計了有效率的處理流程，使得雙核心能夠分工處理各自的運算，並且達到影音同步的功能。除了提出與平台相關的最佳化之外，我們亦提出根據編解碼器本身架構的精簡及加速方法，更能移植到不同的平台上，增加其應用範圍。 本實驗平台使用TI OMAP5912來做為開發的環境，ARM端主要負責AAC編解碼、包裝bitstreams、資料流的流入流出及週邊裝置的控制；DSP端主要則負責H.264編解碼的運算。此系統在雙核心處理器對於影音資料編碼的同時，將編碼後個別的bitstream包裝成可於一般media player播放的檔案格式輸出並儲存。相反的，已包裝過的檔案也可以將其中個別的bitstream取出，交由OMAP5912來完成解碼的工作。此系統的輸入資料可由USB camera、麥克風做為即時影音編碼的輸入，或將儲存於CF卡中的原始影音檔作為處理的輸入。因此，此設計更適合應用於移動式嵌入式裝置、影像電話或視訊會議等不同的應用。

In this thesis, an H.264 and AAC codec synchronization system which fully utilizes the dual-core characteristics is proposed. Due to the restrict resources of the embedded system, several optimization methods are proposed. On the one hand, in the algorithm level, the complex computation of audio and video codec is further simplified. On the other hand, in the memory level, the usage is minimized. In order to coordinate the manipulation of the audio and video data in each processor and synchronize them, an efficient data flow is presented. In addition to the platform-dependent optimization methods, the simplification for increasing the overall speed by modifying the architecture of the algorithm are also developed. Moreover, they can be ported to other similar platforms to enhance the applications. The proposed system adopts TI OMAP5912 as the development platform. ARM takes charge of AAC codec, bistreams packaging, and the control of I/O and peripherals, when DSP is responsible for H.264 codec. Meanwhile, encoded bitstreams can be split into audio and video data and be sent to dual-core processors for the decoding them, respectively. The system can adopt USB cameras and microphones as the real-time sources, or use the raw media files saved in CF card as inputs. Therefore, this design makes it more suitable for applications such as mobile embedded devices, video phones and video conference.