Creating a Dual - Processor Architecture for Digital Audio

you need to be sure that this type of architecture makes sense. Certainly, if you already have one or both of the desired applications running on their own, combining the functionality by integrating the two processors is a logical solution. This type of architecture also provides for a logical division of functionality, including letting the DSP focus on the key algorithms. The DSP of course is fully capable of supporting a standalone application, but if you already have an existing host application, using the DSP as a digital audio “engine,” or coprocessor, will enable you to add this functionality with minimal impact to the existing design while taking advantage of the proven algorithms on the DSP. This logical separation also allows for modular development, improved maintenance, and easier enhancement capabilities. To demonstrate this concept, let’s examine how Indesign used the DSP-based MP3 encoder application from the Internet Audio group to add MP3 encoding to a host application. Figure 1 shows block diagrams of the existing applications. The audio application, running on the TMS320C5416 DSP, is designed to be a self-contained program, including user interface (display and keypad), data input (codec), data output, and media storage (Compact Flash), along with the core encoding engine. PCM data is received in real time from the I2S codec interface, processed through the encoder, and stored in the Compact Flash. The host application contains a user interface, a hard disk drive, and a CD-ROM drive. The new dual-processor architecture is shown in Figure 2. It retains the user interface (UI), the media interfaces, and the existing features from the host application. We added a UI for the encoding feature, an encoding API, and a DSP driver to the host application. The DSP retains the core MP3 encoding engine and changes the input and output data sources. The host application now sends the input (PCM) data to the encoder, and the encoder sends the output (MP3) data to the host, all via the Host Port Interface A dual-processor architecture is a great way to add digital audio to an existing host application, but care must be taken.