this post was submitted on 05 May 2024
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Privacy
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As OP said volume leveling is acceptable, something like this will do.
Modifying HDMI video signal is simply impossible due to DMCA and bla bla bla. But not all hope is lost though. You can overlay opaque video on top of another encrypted stream via this little box. This is an old project per se and I have no idea if still available, but with some dirty work you might able to detect the increase of volume or match of an algo or something with a total black screen overlay on top.
Yes those are FPGA/ASIC based solutions like I mentioned. That should work for 1080p at least, but getting to 4k is still prohibitively expensive.
My understanding is the DMCA explicitly allows reverse engineering of encryption for interoperability purposes... the only problem is that would have to specifically be tested in court to know if the government would agree in this instance, and nobody wants to try it.
Overlay isn't transcoding. All it need is a muxer like MKVToolNix. I doubt it need much processing power.
Muxing has nothing to do with HDMI
It doesn't and I didn't ever mentioned HDMI in my reply. Just doubt if overlaying another encrypted stream with a muxer ever need that much processing power to the point of "prohibitively expensive".
Encrypted streams also don't have anything to do with a muxer, I really don't understand what you're trying to say. Muxers are for handling file formats, which is not being discussed at all, this is about raw video frame processing in hardware.
Well, I'm simply reciting what is described on the page based on my understanding. From the diagram, it does not do raw frame processing from the source (assuming HDMI w/ HDCP) as the stream remains encrypted. By the look of it, it is copy or passthrough to the muxer (as it labeled). With some magic, it muxes two encrypted streams into one and output to the video sink. How is that done I have no idea.
That diagram is describing the hardware side of the NeTV, which is an FPGA device doing all this. That "mux" is describing a hardware 2:1 mux on the raw video streams, such as https://vlsiverify.com/verilog/verilog-codes/multiplexer/
The "magic" is described here: https://www.bunniestudios.com/blog/2011/implementation-of-mitm-attack-on-hdcp-secured-links/
Got it. I can see where the problem is niw and how can the hardware is limiting. Thanks for the great article.