742MHz sounds suspiciously like a harmonic of the 74.25MHz max TMDS clock
rate for a Category 1 cable per the HDMI 1.3a spec.  I don't have the HDMI
2.0 spec (not an adopter), but would love to know more about the test
configurations.  A few thoughts/tests:

4K resolution at lowest color depth (no Deep Color) and lowest frame rate
(i.e. lowest bit rate remaining at 4K resolution)?

Video sources with and without HDCP support?  HDMI test pattern generator
(Quantum Data, Kramer, etc.)?

Comparison of several cables with Category 2 grade?
http://www.hdmi.org/learningcenter/Premium_HDMI_Cable_Participant_List.aspx
-- specific mention of EMC testing as part of qualification; see
Participants list of you haven't already confirmed your cables

Do you have a tool/development environment to access Sil9777 registers for
lower level debug?


Will be interested to hear what others have to say on this.


Regards,
Adam


On Sat, Oct 15, 2016 at 6:57 PM, Brent DeWitt <bdew...@ix.netcom.com> wrote:

> I’ve been working with some Silicon Images (Lattice Semi) 9777 multiplexer
> chips lately and would appreciate any insight list members might have.
> When used at any resolution below 4k, there seems to be a 10 dB emission
> “pedestal” that stands out of the baseline emission at several frequencies,
> 742 MHz in particular.  The pedestal is 666 usec long and repeats at
> whatever frame rate is selected.  At first, I thought it was correlated
> with the SPI bus activity, since the timing was identical, but further
> experiments show that not to be true.
>
>
>
> My question is, is this inherent to HDMI, or to the 9777?  As is probably
> obvious, I don’t have a whole lot of experience with HDMI video.
>
>
>
> Thanks all!
>
>
>
> Brent DeWitt, AB1LF
>
> Milford, MA
>
>
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