We are using an ADV7842 as a front end analog to digital decoder in a set top box design. Our customer has a HDMI camera and has asked us to support its 1280x720 30hz resolution. They have supplied the video signal timings, which are listed below. I don't have their camera and am testing with a video pattern generator that has been programmed with the exact values. The problem I have is that the VERT_FILTER_LOCKED (HDMI reg 0x07) will not lock. The horizontal measurement parameters such as the front porch, active width, back porch, etc. match what I programmed the pattern generator with, but the vertical measurements are bogus due the vertical not locking. I have no problems detecting other SD or HD resolutions up to 1080p60 and am stumped why this one is a problem.
Can anyone please advise why this particular resolution will not lock? The customer says the camera timing matches the CEA-EIA-851-E specification.
Here is the 1280x720 30hz video timing information from our customer;
Pixel Clock Freq: 74.25MHz
Horizontal Freq: 22.50 KHz
Vertical Freq: 30Hz
Vsync: 5 pix
Hpackporch: 1720 pix
Htotal: 3300 pix