AnsweredAssumed Answered

ADV7611 with MPEG decoder

Question asked by PetV on May 9, 2013
Latest reply on May 17, 2013 by mattp

I have a special application using an MPEG decoder chip and the ADV7611 on the same board.

I need the 8 (SD) and 16 (HD) bits wide parallel video data of the decoded MPEG video stream for further processing but the decoder chip has only HDMI output. So I try to get this  video data using the decoder as a HDMI source and the ADV7611 as a HDMI receiver inside a same circuit.

The TMDS outputs of the MPEG decoder is connected directly to the TMDS inputs of the ADV7611.

Unfortunately I found that the ADV7611 cannot lock to the input signal.

When the input video format is 720x576 50i and I use the script 6-1d I get the LLC signal switching between 13.5 MHz and 27 MHz randomly.

To get 27 MHz clock I have to do the following modifications:

98 19 83 -> 98 19 8F

68 8D 04 -> 68 8D 3F

But the frequency of this clock signal is not stable. I measured large jitter although the input RXA_C- and RXA_C+ (coming from the decoder) are exactly 27 MHz and stable.

The detected video parameters by the ADV7611 (pixel number, line number, etc.) are not correct also.

The other video formats don't work also.

The TMDS signals of the decoder are correct. I tested the HDMI output in another circuit containing the same type of the decoder chip using an LCD TV set with HDMI input.

 

What should I modify to achieve correct locking?

 

Thanks,

PetV

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