CRC testing in video applications

September 24, 2013 // By Michael Corrigan and Joe Triggs
CRC testing in video applications
Michael Corrigan and Joe Triggs of Analog Devices consider the benefits of CRC testing in video applications.

Introduction
Quantifying the impact of a small engineering change in a complex video signal chain can often be a thankless task; evaluating whether a lower cost digital video cable has degraded system performance; whether a power supply tweak has increased the system's jitter tolerance; whether an alternate PLL configuration has provided greater power supply noise immunity; typical challenges which the design and production engineers of today's video product design and manufacturers must overcome.

Although numerous video evaluation tools are available to assist in such activities, these often consume significant portions of capital budgets, take time to setup, require training to operate properly, and offer results which can be difficult to interpret. A simple error detection algorithm such as a Cyclic Redundancy Check (CRC) can be used as an effective tool, despite a number of limitations, in advance of investing significant efforts in perfecting systems using the more complicated and expensive evaluation tools; especially when time to market, cost and resources are important considerations.

Digital Video Systems
The proliferation of digital video transmission media for consumer, professional and automotive applications in recent years has triggered a change in the focus for many video product design and manufacturers; the requirement to achieve superior analog performance has plateaued and has been superseded with a demand to achieve the highest possible digital data rates possible. These transmission media include DVI, HDMI, LVDS, MHL and APIX.

The growth of HDMI has been one of the primary drivers in this race to higher data rates. At its inception, support for video transmission at up to 1.65GHz facilitated the transfer of 1080p video (1920 pixels x 1080 lines) with an 8-bit colour depth - a video format offering over ten times the video resolution of analog NTSC video. Further developments to the HDMI specification in recent years have seen the data rate of the maximum supported video resolution stretched through 2.25GHz to 3GHz with further increases most

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