Three-step test verifies video equipment
Martin Rowe, Senior Technical Editor -- Test & Measurement World, 2/1/2007
MT VERNON, NY—Key Digital Systems manufactures audio and video distribution amplifiers and cables. Often found in sports pubs, hotels, and in some homes, the amplifiers take in analog or digital video from DVD players and set-top boxes and distribute it to TVs in either digital high-definition multimedia interface (HDMI) format or analog format.
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Engineering tests of video distribution amplifiers consist of physical-layer tests, protocol tests, and interoperability tests. |
Tests start with the physical-layer (PHY), where systems and hardware design engineer Yury Wolf-Sonkin checks eye diagrams on the HDMI streams for compliance to standards. He uses a 6-GHz real-time oscilloscope with built-in HDMI-compliance software to analyze the eyes. “PHY testing comes down to eye openings,” said Wolf-Sonkin. “The eye must have at least a 38% opening at the receiver.”
The remaining tests revolve around software. Wolf-Sonkin uses an HDMI protocol analyzer to verify that a distribution amplifier’s transmitted video and audio streams meet specifications. It also checks video sources for HDMI implementation.
Because a distribution amplifier must connect to both a video source and to a TV, interoperability testing requires connecting a distribution amplifier to a wide array of products that lets Key Digital engineers find problems so users won’t.
“The HDMI standard leaves some things open to interpretation,” said Wolf-Sonkin. Thus, an HDMI stream may not be compatible with every TV. Interoperability testing lets Key Digital engineers verify that a distribution amplifier’s software can handle these issues.
Sources of information about HDMI testing:
“HDMI Compliance Testing Policies and Procedures”
www.sony.net/Products/HDMI/HDMICTP1.P10.10.05.pdf
HDMI FAQ, HDMI Licensing, Sunnyvale, CA, www.hdmi.org/consumer/faq.asp
“HDMI Sink and Source Compliance Test and Characterization,” application note 5989-4959EN, Agilent Technologies, October 2006. cp.literature.agilent.com/litweb/pdf/5989-4959EN.pdf
"Physical Layer Compliance Testing for HDMI Using TDSHT3 HDMI Compliance Test Software," application note, Tektronix, July 2006.
www2.tek.com/cmswpt/tidetails.lotr?ct=TI&cs=Application+Note&ci=2166&lc=EN
La Maestra, Rodolfo, “HDMI Part 8 - Cables for 1.3,” HDTV,August 29, 2006. www.hdtvmagazine.com/articles/2006/08/hdmi_part_8_-_cables_for_13.php
"What's a ‘Certified’ HDMI Cable?"
www.bluejeanscable.com/articles/certified-hdmi-cables.htm
