Making a HDMI audio type detector

not really an arduino specific question. I want to make a device that goes inline on a HDMI to detect what type of audio it is (PCM, dolby digital, dolby digital+...) which I know is possible as you can normally see it on a tv or amplifier but not sure how to approach it? Can anyone help me out with some ideas?

I think you’re in the wrong forum, unless you’re looking at one of the FPGA devices.
HDMI data rates are way beyond what any of the typical Arduino devices can even think about looking at.

Thanks, I was thinking I can make some sort of capturing using one of the pin out from the HDMI so I can just use an arduino to process it and display it using a small screen. After a bit of googling it seems and as you said a lot more complex then that as you have to look at the EDID and infoframe with one of their decoding chip which is not available unless you are a AV equipment manufacturer or have a super expensive licence.

The data rates are nearly 4 orders of magnitude beyond what the Arduino can easily bit-bash, to put this in context, and impedance-controlled LVDS so trying to hook into the signal would likely load it down too much.