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Using phase reversal to cancel music for Dialogue?
Hi.
I’m cutting promos with a film which has stereo full mix on channels 1 and 2 and Stereo Music and Effects on channels 3 and 4. I’ve been told that laying all 4 channels into a timeline and then placing Audio Suite’s Invert Tool on Channels 3 and 4 will cancel out the music that exists on channels 1 and 2 when all 4 channels are played together as a stereo mix. This is ostensibly using Phase Reversal.
It does not appear to work. I was just wondering if this in fact is not true?
Steve
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8 Replies
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I’m not familiar with the Invert option in AudioSuite. I do know that the 1-band EQ for instance has a phase inverter button. I usually use that to flip phase. You will need to render. Also, there might be a very slight processing delay, so it might be best to use the same AudioSuite effect on all tracks, but only flip phase on two of the four.
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Phase reversal would remove the dialogue not the music.
Why?
Phase reversal says that sound wave can be cancelled by a soundwave that is exactly opposite. If you take a mono signal. and invert it, then combine it, it should cancel.
Dialog tends to be a mono track spread across the stereo channels.
Music is stereo and therefore should be different on each side.
Terence Curren
http://www.alphadogs.tv
http://www.digitalservicestation.com
Burbank,Ca -
But Terry, if you have a full mix (D and M and E) and you have an M&E (as the OP describes), and you phase reverse the M&E, and mix it with the full mix, you are subtracting the M&E from the full mix, leaving you with just the dialogue.
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That’s what I get for not reading the entire original post. 🙁
I wonder if the plugin actually works? In the old days we used an XLR cable with the wires reversed.
Terence Curren
http://www.alphadogs.tv
http://www.digitalservicestation.com
Burbank,Ca -
Yes, I was wondering if it works as well. I applied the Invert plugin to Ch3 and 4 (Stereo m&E). It does not seems to cancel out the music on channels 1 and 2 (Stereo Full Mix)
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I just tried it and it works for me.
You need to make absolutely sure that everything is routed and panned the right way.In your example, and assuming stereo out, make sure that the Left part of the Full Mix is on A1, and the Left part of the M&E is on A3, and make sure that both are panned hard left. Right part of Full Mix goes on A2, Right part of M&E goes on A4, both panned hard right.
Apply the invert effect to both tracks of the M&E. Render. Now when you hit play, the M&E should be subtracted from the Full Mix. If that does not happen, either the panning is wrong, or the track assignment, or the M&E and the Full Mix do not line up correctly. Or maybe there are more mix differences, which will show up immediately.If you need to convince yourself that it works, take any piece of audio, just one track, splice it timeline. Add the exact same piece to another track in the timeline. Pan both hard left. Playback, and you will hear the clip at a pretty strong level (adding up the two events of the same clip). Now apply the AudioSuite Invert to one of them and render. Playback and you will hear silence, and the meters of your Audio Tool will be pitch black.
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You are right! Worked great! Thank you both for your valueble input. Much appreciated.
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This sounds awesome! However when I tried the example as Job suggested, I had the audio volume drop down significantly, but not be eliminated??? Interestingly, I can actually see the audio waveform inverted after rendering the track with the “Invert” effect. I used some stock library music for the test. Any ideas?
David Oulashian
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