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Bad audio in video - help!

Discussion in 'Sound, Music, and Intercom' started by TechnicalRunner, Dec 10, 2007.

  1. TechnicalRunner

    TechnicalRunner Member

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    I don't know if anyone here is also a video/film person, but I recently shot a final project for one of my classes and part of it has a hum/buzz. We had to shot on location, and there was an ice cream machine running at the time. We've already tried using noise reduction in Soundtrack Pro, but the problem is the actors' voices are too close to the sound of the hum and it was also dubbing them out. We had to use the boom mic on the camera instead of a real boom (long story), so it's essentially ambient sound. Does anyone have any suggestions on how to fix this? Anything at all?
    - Lisa
     
  2. kwotipka

    kwotipka Active Member

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    Hum, that is going to be a tough one. The problem is as you stated that the voices are near the same frequency as the noise in the room. Your traditional notch filtering isn't going to help you much here.

    Without going into the long lecture about how you should have used correct micing techniques here is one long shot possible attempt. I know that this will not be a magic bullet but here it goes.

    Hopefully at some point you either recorded "room tone" or a long enough segment of ambient sound without anyone talking. This "room tone" is often used to fill in the gaps where editing has created acoustical "dead" spots in the soundtrack. Take this room tone and try to get it into some sort of seamless loop. Now duplicate it until you have enough to cover your bad audio. Invert it 180 degrees out of phase and see if the noise will cancel itself out. You may have to slide the room tone track in and out of sync with the video to help with the effect.

    It will thin out the primary audio some but I have used this trick to some extent between an on-camera mic and a lav or boom with mixed results in post. Now if someone starts preaching about the time delay between the boom and the on-camera mic not being exactly 180 degrees I am going to smack them. This is a rough solution here people.

    kw

    ---edit---

    You may have to go back to the original camera footage because I don't know what STPro did to the waveform for it's noise reduction.
     
    Last edited: Dec 10, 2007
  3. mbenonis

    mbenonis Wireless Guy Administrator Premium Member

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    There are really two options here. As kwotipka said, if you have some room tone, you can use any number of programs to notch it out. For the film I am working on, I'll most likely be using Izotope RX, but there are probably less expensive alternatives out there.

    The second option is to ADR the scene (ironically I did this yesterday for a car scene with terribly location audio). Essentially, this is dubbing it, but with extra care taken to match the re-recorded audio to the location. You'll want to find a quiet location with a little echo as possible. I am very fortunate in that U.Va. has a soundproof booth in which I can record. Set up a computer which can record one track of audio while simultaneously playing back a video clip with audio. I used Digital Performer for this. Be sure you use a boom mic, and not an SM58 or similar. Place it a few feet from their mouths. Then have your talent listen to and watch the clip a number of times and get the exact wording down, and then record a number of takes of them repeating the lines. If they want scripts, be sure to tape it to a wall so that they don't rustle the papers. After this, you may need to add a very slight amount of reverb to match the room, and some fake ambient sound at a much lower level to add to the realism.

    Hope this helps!
     
  4. kwotipka

    kwotipka Active Member

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    Sorry I didn't mention this. I think that FCP2 Studio has a nice ADR tool either in FCP or Soundtrack Pro. Don't quote me on this though.

    kw
     
  5. mixmaster

    mixmaster Active Member

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    Lisa,
    In the perfect world, I would recommend re-recording that segment. However, we seldom live in a perfect world and I often find myself trying to edit noise out of recordings of events here. (separating a quiet flute passage from air handler wind noise during a recital for example) I'm not familiar with your computer program, but I have solved similar problems with Adobe Audition. Audition has the ability highlight a particular part of the track that is just noise then cut that out of a whole section and to control how much a particular tone gets cut. It's usually pretty accurate. If that doesn't work I have also had good luck applying the filters to only parts of a track, like between words or phrases, and letting the noise get "buried" under the words or phrases that I have to keep. If your program allows you to try stuff without destructively editing you file, you may be able to apply some boost to the whole track. Having more signal to work with sometimes help me be more precise in what I cut. It also results in a louder final product and when the final mix is quieted down, sometimes extra sounds get "lost" as noise floor.
    Best of Luck
     
  6. BNBSound

    BNBSound Active Member

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    You could try a simple gate with a fairly slow release time. You'll likely still want to do some creative notching. If your program has an FFT plugin (Real Time Analyzer) you can get a visual on the signal to know better how to EQ it. Once you've got the actors opening the gate with their dialogue, get some compression in the chain to even things out and finish off with some ambient noise of a different type.
     
  7. TechnicalRunner

    TechnicalRunner Member

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    Thanks everyone! I talked it over with the rest of my crew and we decided we're going to re-record the audio and try to match it with the video. I want to just re-shoot the scene but there isn't time; this is supposed to be done by next week and we'd have to go through the process of reserving all our equipment again and calling the cafe we shot in and all that, and it's final exam time so no one really has time. Thank you all for your input, I'm very grateful!!

    - Lisa
     
  8. mbenonis

    mbenonis Wireless Guy Administrator Premium Member

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    Lisa,
    Be sure to re-read my comment above (even if you've already read it). :) It's critical that if you're rerecording things that you be able to playback the movie in sync with whatever you're recording onto. This will allow you to easily drop in the replacement audio with a minimum of hassle.

    Also be sure you rerecord in a very quiet location. Turn off the AC/Heat, all computers, and anything else that could make noise. Keep people out, and avoid all background noise. You'll probably still need to de-noise it later, but it will be easier if you have a very quiet background. Also be sure to capture room tome (15 sec worth or more) to use as a noise sample.

    Finally, don't try to do it in one take, two takes, or even three takes. Let the actors watch the clip (the final edited clip preferably) about 5-10 times before doing a take. Make sure they have the words down perfectly. Then do a bunch of takes. I did 8 the last time I ADR'd. Then you have options when you're editing the audio as to which clip you want to use. It's going to take 2 hours if your clip is short (<2 mins); more if it's longer - plan for that too. Don't try to rush it; it won't work well in that case.
     
  9. SHARYNF

    SHARYNF Well-Known Member

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    A trick that is worth trying is to use a two step process, first run the audio thru an expander, (opposite of compressor) this should bring the desired audio level above the back ground noise, then use use a good noise eliminator like sound forge has sample a small part of just the "room with noise sound" and use this to eliminate the noise

    This should help
    ADR is great but if you are not experienced at it in can be tricky

    Sharyn
     

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