Digital set-top boxes (DSTBs) receive and decode television broadcasts from satellite, cable, and/or terrestrial sources. Integrated digital televisions (DTVs) have built-in digital tuners, demodulators, and source decoders, so they do not require digital set-top boxes that receive digital broadcasts.
Traditional DSTBs are designed to receive standard definition (SD) Moving Pictures Experts Group-2 (MPEG-2) video format broadcasts. However, many of today’s DSTBs are high-definition (HD)-ready. In fact, selected cable television service providers, networks, and local terrestrial TV stations are concurrently transmitting both SD and HD content. Over time, MPEG-4 will displace the MPEG-2 format for both SD and HD.
When MPEG-4 becomes the standard compression standard, systems implementing reprogrammable logic devices (such as Altera® FPGAs) will be able to seamlessly upgrade without having to scrap inventory items or make new hardware. Using FPGAs, manufacturers can design a STB that can decode MPEG-2 video format, and then later upgrade that same STB for MPEG-4 by simply reprogramming the FPGA in-system.
High-end DSTBs usually offer personal video recorder (PVR) and/or an HD DVD recorder for Blu-ray functions. Microcontrollers in DSTBs or integrated DTVs can perform a number of functions for these systems, including control panel management and on-screen display (OSD).
Many current DSTBs can be classified either as free to air (FTA) or pay TV versions. A pay TV example would be DSTBs designed for DirecTV or Dish Network (in the USA), which require conditional access to decode the audio and video.
DSTB manufacturers typically design the PCBs for both low-end and high-end DSTB systems and require a flexible solution for implementing their various designs. Figure 1 shows a typical Altera programmable logic device (PLD) solution for DSTBs and depicts one of the wide range of applications that are possible with an FPGA-based solution.