As real-time digital signal processing (DSP) systems become more complicated with multiple threads of execution and faster DSPs, software development and debugging becomes more complicated. An MP3 player is a good example of a multi-threaded system that executes not only DSP-type (data) threads such as MP3 decoding, sample rate conversion, and graphic equalization, but it also runs typical “host/controller” (control) threads such as user interface (keypad/LCD) and access to storage media (for example, Compact Flash). In this document we discuss the software behind a real-world MP3 player running stand-alone on a Texas Instruments C5000E DSP. Parts of this system are presently being shipped in production MP3 players all over the world. The software is built upon the Texas Instruments DSP/BIOS offering with scheduler and real-time analysis. This application report shows a step-by-step real-world software paradigm shift. We will start with a typical ISR (interrupt service routine) system and build it up in steps to incorporate such constructs as a real-time preemptive kernel and data piping structure. Then we will see how DSP/BIOS real-time analysis (RTA) can be used to observe and debug the entire system in real time. These debug features include scheduling graphs, loading calculations, and statistical benchmarking information.……