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I would like to inspect the audio data islands of a 1280x720 progressive scan 60 Hz HDMI signal. I simply want to view these data islands to see exactly when audio data begins to be transported in the data islands relative to another signal (an analog audio signal generated by an HDMI audio DAC. I can convert this to a digital one if it makes things easier). What specifications would be required of a logic analyzer to do this?

Related: is there a hardware TMDS receiver/decoder that I should be using or is decoding something I can do in software/with the logic analyzer? I do not want to reconstruct the audio signal, so I am not interested in an HDMI receiver that regenerates the audio clock and provides an audio stream. I am not concerned about noise, so I don't expect to need to make use of the balanced signals; if there is a bit of error in the readings from time to time that should be fine for my purposes.

It appears that the TMDS clock frequency for this signal is 742.5 MHz. Some articles that shed light on the workings of HDMI are here and here.

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    \$\begingroup\$ A logic analyzer itself is not the right tool - you need a HDMI protocol analyzer. \$\endgroup\$
    – Justme
    Jun 28, 2021 at 14:12
  • \$\begingroup\$ Thanks, Justme! I didn't know the term, but now I know exactly what to look for. I guess I could just bootstrap my other signal that I would like to compare against wiring it up to the CEC pin? I expect this would show up in the inspector of the HDMI protocol analyzer? \$\endgroup\$ Jun 28, 2021 at 15:18
  • \$\begingroup\$ The CEC pin is for CEC, and for that you need CEC protocol analyzer. \$\endgroup\$
    – Justme
    Jun 28, 2021 at 16:00
  • \$\begingroup\$ Hmm. I see that some HDMI protocol analyzers have trigger input. Maybe using this to denote an external signal is the right way to go about this... Before dropping $10,000 on something, I'd need to know it would work, mind you. Maybe there's a place I could rent time with one... \$\endgroup\$ Jun 28, 2021 at 16:14
  • \$\begingroup\$ @AllenPestaluky Do you want to decode HDMI or HDMI 2.1? \$\endgroup\$
    – Voltage Spike
    Jul 6, 2021 at 16:01

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Disclaimer: I am not a reseller, and this is just experience sharing.

I used to work with HDMI video at work, we had two tools for this:

  • Quantum Data Analyzer, a HDMI sink/source to test HDMI compliance. I don't think you can extract the audio data with it.
  • Omnitek 4K Ultra Toolbox, a 4K HDMI/SDI/6GSDI Analyser/Generator/Converter. This tool was powerful, and it allows you to get pixels values, blanking values, and everything useful to develop video system. I think it can also display audio content (did not use audio in HDMI so I did not tested the audio capabilities).

These tools are not cheap, and if it is just for personal understanding, I would suggest to rent it.

Note: QuantumData seems to be owned by TeledyneLecroy, and there is more recent products than the one I worked with. Maybe you can try to contact them to have more information on their products.

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  • \$\begingroup\$ Thanks, PierreOlivier! This isn’t exactly the type of answer I was hoping for, but the intent here seems to be the right approach: to determine the specifications I need for a logic analyzer or an HDMI protocol analyzer, I should contact the manufacturers of this equipment and get them to help me. Then, the best course of action will likely be to rent the equipment for my uses. \$\endgroup\$ Jul 13, 2021 at 13:05

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