audio de-echo filter?

Discussion in 'Professional Video Production' started by peter, Feb 16, 2006.

  1. peter

    peter Guest

    Is there such a thing as audio de-echo filter?

    Some of my recordings done with on-camera mics would sound better if I could
    remove some of the echo.
     
    peter, Feb 16, 2006
    #1
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  2. "peter" wrote ...
    There are some high-end solutions which likely cost several times more
    than your camcorder costs, and take significant experience to operate
    effectively. http://www.cedar-audio.com/

    For amateur use, you might be able to get some improvement by
    "gating" the audio track. i.e. substantially reduce the volume of any
    part of the track that is not as loud as the dialog, etc. Some software
    will do this automatically, but we don't know what you are using?
    On-camera mics are not useful for recording anything beyond
    background sounds/noise. They were never meant to pick up
    anything important more than 12 inches away. Yes, people who
    make cameras (and some who make after-market microphones)
    will make you think you can record everything from a camera-
    monted microphone. But consider this: You have likely NEVER
    heard anything in a theatre that was record with an on-camera
    microphone. And you could go for weeks without hearing any
    camera-mic audio on TV (even run-n-gun news & "reality" shows.)

    We have not yet found a work-around for the laws of physics.
    Decent sound requires getting the microphone closer to the talker.
    Hand-held, clip-on lapel, boom, wireless, whatever. But unless
    you are shooting close-ups for pimple cream or tooth-whitening
    gadgets, the on-camera mic is just too far away.
     
    Richard Crowley, Feb 16, 2006
    #2
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  3. peter

    blackburst Guest

    Amen!

    There is no miracle procedure to correct badly-recorded audio. If you
    want it to sound good, record it the correct way. generally, ACAP - as
    close as possible (except in a rare overload situation.)

    I preach this to my students all the time, and to my staff. A pro on my
    staff was set up to close mic a comedy performance, and the MC said he
    wanted lots of crowd noise and told him to use the camera mic. And he
    did. And the audio is unusable.
     
    blackburst, Feb 16, 2006
    #3
  4. peter

    EricS Guest

    == 1 of 3 ==
    Date: Thurs, Feb 16 2006 5:44 pm
    From: "peter"

    Is there such a thing as audio de-echo filter?

    Some of my recordings done with on-camera mics would sound better if I
    could
    remove some of the echo.


    As others have pointed out, there is almost NO way to remove
    reverb/echo, particularly because it is the same sound as that which
    you are trying to keep, but in any case, removing unwanted sound is not
    an easy task.
    Sound, not video, is the hardest thing to capture properly.
    I would suggest you get your subject(s) back in again if possible, loop
    the video on your computer and get them to re-voice the important bits.
    Or do a narrative voice-over with music between phrases.

    There is only one situation where on-board microphones are of use I
    have found, and that it is to capture general ambient sound.

    Eric from Oz
     
    EricS, Feb 18, 2006
    #4
  5. peter

    DanR Guest

    Sometimes even the pro is stuck recording audio (voice) in a very live boomy
    environment. One gadget we used years ago was a CAT43 card that replaced the
    main plug-in card for one channel of Dolby analog noise reduction. It had a
    remote unit with 4 or 5 fader type controls. In reality it was a group of gating
    circuits that gated different parts of the audio spectrum independently with
    various attack and release times. It was always able to help some and sometimes
    a lot.
     
    DanR, Feb 19, 2006
    #5
  6. peter

    Ty Ford Guest

    Yep and George Massenburg designed a six fader piece for Disney some years
    back to noise reduce some of the early Disney Optical tracks as well. I
    reviewed it and it actually did reduce sloppy echo stuff. I think the basic
    concept is used in the Cedar system.

    A tribute to man doing what he can to fix something that was not done
    properly the first time.

    Regards,

    Ty Ford




    -- Ty Ford's equipment reviews, audio samples, rates and other audiocentric
    stuff are at www.tyford.com
     
    Ty Ford, Feb 19, 2006
    #6
  7. peter

    neckbeard

    Joined:
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    serial correlation

    Mathematician here. The lack of a de-echo filter has puzzled me before too. Why can't you just treat an echo as autocorrelation? Surely if you plotted a residual of x(t) - x(t-1) you could come up with at least a slightly helpful filter that kills some of the echo, some of the time -- right?
     
    neckbeard, Apr 29, 2011
    #7
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