Case study

Consumer grade digital TV receivers (Set Top Boxes) are extremely efficient in providing good customer output, i.e. tv streams, yet they are of not much use when stream quality monitoring needs to be performed. In such a case a technological twist is needed. This is quite the case for some of important stream quality parameters such as equalization taps, constellation, Eb/No and similar. In other words, if there is a demand to analyze the signal quality consumer grade chipsets cannot provide the needed output, yet, they do provide stream outputs. In addition to all of this data, the product needed to minimize the use of PC resources and have a broadest possible span of frequencies within the industry.

Solution

Prior to making key design decisions, additional requirements has to be specified for the particular case. The design can be a PCI/PCIe form factor capable of supporting both terrestrial and cable DTV standards and it is also required to both provide stream output as well as parameters readings.

This is all solved by basing the design around an FPGA with an external DDR buffer, to be used both for stream and data sampling for FPGA based constellation analysis. PCI and PCIe interfaces are implemented as well.

Still, the most difficult challenge here is to get a set top box alike silicon tuner and stream demodulator fully working with minimal support. Namely, the STB chipset providers were not in position to provide full support and most of the functional aspects had to be solved by Bitgear, turning this FPGA system into a quite demanding engineering task. All in all, the system has been made to work according to the specs and is currently in production.

Added Value

• Real time stream logging
• Fully available channel parameters
• Linux and Windows API fr smooth integration