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ADV7604 HDMI-GR 720p23.98/24

Question asked by andrewp on Jun 23, 2014
Latest reply on Jul 11, 2014 by andrewp

Hi,

 

Does the ADV7604 support 720p with a frame rate of 24Hz or 23.98Hz? Our product doesn't seem to work at this resolution + frame rate. 720p25 and higher frame rates are fine.

 

The ADV7604 seems happy, reporting a TMDS clock of 74MHz and the following STDI data:

 

720p24 input:

 

        stdi1: 0xB1

        stdi2: 0xAE

        stdi3: 0x2A

        stdi4: 0xED

        stdi5: 0x12

        stdi6: 0x34

        interlaced: 0

        block_len: 12718

        lcvs: 5

        lcf: 749

        fcl: 4660

        field rate: 24.004459            // XTAL_FREQ / ((fcl * 256);

 

The symptoms we see are described by our FPGA guy:

 

"On some occasions I've definitely seen the input to the FPGA (output of the dvi rx chip) being complete garbage when trying to receive 1280x720p23.98. For example line lengths of ~2000px or ~800px or some lines without the data enable going high."

 

I've seen this post: ADV7604: Analog and digital support for 720p30? Which suggests that 720p30 isn't supported due to: "the length of the horizontal blanking period of this video format. It is more than half one line length which overflows an internal counter." However 720p30 works fine for us. For reference the timing data we are using for 24Hz is:

 

h total: 4125

h position: 260

h active: 1280

h sync: 80

v total: 750

v position: 25

v active: 720

v sync: 5

 

I just want to check that this is still the case and there is no known work around.

 

EDIT: This seems to be directly related to the horizontal line length, >= 4096 pixels (porch + active + sync + ...) doesn't work, < 4096 is fine. We feel this is a problem with our video source, since a line length of 4115 pixels with only 1280 of them active, seems ridiculous. It would be nice to work around this, but can understand if it's not supported.

 

Thanks,

Andrew

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