A DSP Based Multi-Format Video Decoder for an IP Set-Top Box

In this paper, the implementation of a digital signal processor (DSP) based multi-format decoder for an IP set-top box is described. Using several software optimization techniques, the multi-format decoder has been fitted into a TMS320DM641 DSP @ 480 Mhz. Starting from a native C code implementation, a six-step software optimization process has been applied to improve the decoder performance. Currently, 30% and 54% of the DSP capacity is used for MPEG-2 MP@ML and MPEG-4 ASP@L5 decoding, respectively. As a result, the cost of the whole system is lowered since the DSP has enough room left to run other IP set-top box tasks such as transport stream parsing, audio decoding, audio and video presentation and a user interface. Nowadays, our middle term goal is to fit other video decoders (H.264 and HD MPEG-2), other audio decoders (AC3 and AAC), a Real Time Operating System (RTOS) and a complete user interface in the DSP.