Extract stereo audio from (possibly HDCP protected) HDMI, is that possible?

[Ranayna]

Hi everyone,

this is a general interest question at the moment. There is a small project on my horizon about building a small stereo audio mixer. But for that to be really useful for my application, I would need the ability to mix in HDMI audio. The video would have to be passed through. The maximum resolution of my screens is 2540 by 1440 (WQHD) but FullHD would be enough. The source cannot go over FullHD anyway.

Now I know that HDMI is a huge can of worms. Easiest of course would be just buying one of the many available HDMI audio splitters available on Amazon or Ebay. But I want to at least check if it is feasible at all building such a thing yourself, to fully integrate it into a mixer.
I have looked at a couple of Analog Devices chips, that while quite expensive, look like they might fit the bill. ADV7623 for example. But that already has more features than I need, making it more expensive than it needs to be.

Any pointers to alternatives would be appreciated. I hope the verdict is not just "forget about it"


Greetings,

Ranayna

[jc101]

You can get an audio de-embedder for not much these days, even with 4K passthrough of the HDMI...

https://www.lindy.co.uk/audio-video-c2/converters-scalers-c105/hdmi-4k-audio-extractor-de-embedder-p10032

Naturally if you want to build something in, you will need to pass the HDMI through without impacting that.

[Ranayna]

I know about devices like those. Maybe someone who has one can check what chip they use?

Of course I can rip it out of the case and integrate it into a mixer. But that is an inelegant solution, and my biggest problem with that is the fact that the two HDMI ports are on opposite sides.

[jc101]

It's a bit of a pain, as the audio will come out in SPDIF, that you'll then also need to decode via a DAC to get an analogue audio output. As you want passthrough for the HDMI then you will also need to regenerate it and send it out again.  Chips like those you mention can handle the HDMI in/out but you'd need to add in the SPDIF decode too.  If this is a one off, then a de-embedder will save a world of pain. 

There are more professional units with all the connectors on one side, but they are naturally much more expensive.

https://www.extron.com/product/hae1004k

[Bratster]

IMO for a one off I would get an off the shelf audio extractor that does what you want and then extend the HDMI ports to the case of your project with some bulkhead connectors along these lines:

1ft Hi-speed Hdmi 1.4 Ethernet Channel M to F Panel Mount Extension Cable https://www.amazon.com/dp/B00DHO3DGY

Sent from my Pixel 2 XL using Tapatalk

[Doctorandus_P]

There are some HDMI extenders and splitters of which the keys have leaked.
With such a box you can do with the audio as you like. I believe there are even some Open Sourse projects to add PIP and other things to the video.
Searching for hdmi in combination with fpga might be usefull:
https://duckduckgo.com/html?q="hdmi"+"fpga"