Whoa! Give it a rest, guys.
if you record it or not, or if it's illegal or not. Vio just wants to get some audio on his private flying video. It's no big deal.
Meanwhile, back on planet Earth.....
The way to do it, is to buy a mini-electret microphone from your local electronics shop. Connect it to a standard lead, if it doesn't already have one, with a standard audio plug at the end. That goes into the audio-in socket on the video camera.
Then put the microphone inside the ear-cup of your headset. It works very well with active noise cancelling headsets but it's fine with passive ones too.
You will have to do some experimenting with recording levels, but it's far easier to deal with that than to mess around with getting a direct feed from the aircraft's own intercom.
There, you get ATC, intercom, and everything else you would want, minus the engine noise.
Next trick: For communications failure, or when you want to tell someone to "look up and wave!", the same method can be used with your mobile phone.
Put the earpiece of the hands-free kit in your ear, under the ear cup of the headset, together with the hands-free microphone, and then talk normally
but remember not to press the PTT button!
It works surprisingly well and doesn't affect the ability to communicate on the radio.
Now for communications failure you can calmly look up the phone number of the ATSU you were supposed to be talking to and explain the situation with them instead of ... well can you remember what to do? when the heat is on?
(If you are thinking of telling me that this is illegal too, please save your breath).