DVDFab Forum - Tech quesiton on Cinavia and BD Audio


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Tech quesiton on Cinavia and BD Audio

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  • Tech quesiton on Cinavia and BD Audio

    I've seen a few older posts that Cinavia may possibly be triggered by a string of (blank) millisecond (mS) gaps in the audio soundtrack. Obviously, a few mS of silence would be imperceivable, but in the digital world, that's a long gap that can be easily detected. One person said they added low level pink noise, but it wasn't said whether or not this worked or not.

    From an audio engineering perspective, pink probably isn't the best to use because you can hear it, but perhaps mixing a 5-10 Hz signal onto the soundtrack would be a better choice. I don't know what the low frequency specification limit of BD (i.e. AC3) audio is, but I'm guessing its probably 20 Hz. If this is the case, then mixing a 5-10 Hz (sine, square, triangle, etc.) signal "may" be enough to fool the player into thinking that Cinavia isn't present but low enough so as not to pass this low frequency signal through the audio outputs being <20Hz, again assuming that Cinavia is keyed by these mS gaps in audio.

    On the other end of the spectrum, you could use add say a 22 kHz signal instead, but this too should be filtered out at the audio output as it's probably limited to 20 kHz, but to the audio decoding circuits, 22kHz is just as a valid an audio signal as any.

    Another unknown, is that although DVDFab and others can rip the BD disk's with the DTS (other other HD audio) to AC3 5.1 (as are the new releases on DVD soundtracks), is there any information as to which channel, if one or all, that Cinavia is encoded on?

    To that end, there are several tools out there that can split an AC3 5.1 soundtrack into individual WAV files that can be remixed to include some background signal, then reassembled to a single AC3 5.1 soundtrack file. Yes, its a lot of work, but doable.

    I know this is a long shot, but it's an interesting theory anyway.
    Last edited by billw; 09-10-2015, 05:01 AM.