CRC testing in video applications: The stages of CRC

October 06, 2013 // By Michael Corrigan and Joe Triggs
CRC testing in video applications: The stages of CRC
Michael Corrigan and Joe Triggs of Analog Devices examines the various stages of CRC testing in video applications.

The Stages of CRC

Development Phase...
CRCs can be employed across many facets of the development phase of a video product to gauge the performance of the video signal chain; during thermal testing; during power supply testing; during the assessment of layout changes, during final software configuration changes; even during cable selection if a cable is to be supplied with the product.

Compliance Testing
Before a video product can be marketed as HDMI compliant and carry the HDMI logo, the product must undergo a series of stringent test at an officially licensed HDMI approved test centre (ATC). These tests ensure that the product meets all of the requirements set out in the HDMI compliance test specification (released in alliance with the main HDMI specification). One of the toughest tests conducted as part of this suite of testing is an analysis of how robust the video receiver is to jitter on both the clock and data channels.

Meeting the criteria outlined in this test are quite often challenging and video product design and manufacturers frequently send their prototype systems to for expensive pre-compliance checks if they do not have access to the ultra expensive equipment specified in the official tests.

The frame checker in the ADV7850 can be used as a low-cost substitute for early iterations of pre-compliance testing if the specified equipment is not available; it provides an insight into whether the receiver is correctly receiving and decoding the HDMI data (factors which can influence this range from whether the correct configuration writes are being employed, to power supply design).

If the specified equipment is available, the frame checker can still be employed as it provides a definitive insight into whether the receiver is correctly receiving and decoding the data. This level of analysis goes beyond that mandated by the CTS which mandates only visual checking.

HDMI Cable Selection
Many video product design and manufacturers, especially in the professional audio/video

Design category: 

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