Noise Cancellation (nullification) app with sterio mic input?

Discussion in 'iOS Jailbreak & Cydia' started by SkankyToast, Jul 24, 2010.

  1. SkankyToast

    SkankyToast New Member

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    Well, I just got back from a 2 week RV trip to yellowstone, and the entire way, noise was terrible. I had to pump my ATH-m50s to 75% volume on my iPod touch! I thought.. Boy, I wish I had some noise canceling headphones.

    Then another thought crossed my mind. When I last used noise canceling headphones (the best of the best, 375$ bose) They were excellent at cancelling noise, but the sound quality of the speakers kind of sucked in comparison to my M50's

    I didn't know much about noise cancellation, but I knew that microphones took ambient noise from outside, and added an inverse to that noise to nullify the wave. So my idea was to add mics to the outside of my good quality headphones, and ether make a circuit (like the headwize byRyckebusch) or possibly eliminate the circuit, and do the calculation at the SOURCE! My iPod Touch, and add it in-line to the output (my headphones)

    The only problem? I don't know much about the iPod touch SDK, or hardware.

    So, I thought this might be a good forum to look on for help.
    I was thinking of putting the mic inputs as pins 12 and 13? I need a better analyzation of the pinout Apple iPod, iPhone (2g, 3g), iPad Dock connector pinout and wiring @ pinouts.ru that would let me put the right and left mics in, and use the signals that come from them.

    Then there is the question of the iPod using that signal, and having a mix of direct de-amplification, and an algorithm like the one used in the bose headphones to still allow you to hear people talking to you.

    This is a fairly large project, but hopefully hardware will be minimized if I can find a way to get input directly into the iPod.

    Thanks!
  2. ZhiZhi778

    ZhiZhi778 Member

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    if you own 2nd/3rd generation iPod Touch then you can use a headset with mic included liek the stock headset.
    if not there are mics on amazon or ebay for the dock.

    The problem is for your task you would need a background process which has access to the entire system or at least to the ipod application.
    that is not possible using official SDK so the only simple way to do this is to hire a dev for a jailbreak app on cydia or whatever installer

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    you can use the official sdk and code an app that can play songs itself and then eliminates noise but that would be ALOT of work...and why recreate something that already exists (ipod app)
  3. SkankyToast

    SkankyToast New Member

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    Did you even read the whole post?

    no, no, I would use a STEREO mic, meaning there are right and left mic inputs. since there is only room for mono input in the actual headphone/mic jack I would wire something up that goes into the dock connector.

    The app would have to have access to the pins that are receiving the mic signals, and then run them through an algorithm that nullifies the signals, or uses Some code or another to cancel noise. It shouldn't be that hard.
  4. ZhiZhi778

    ZhiZhi778 Member

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    it actually is that hard and yes, I've read the whole posting

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    mono or stereo doesn't matter for this task tho

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    The difficult thing is to code an app that can access system level - if an app demands for audio output any other app that was using audio output before is told to stop it...like this:
    you have your ipod playing a song, then you open last.fm and start to play a song - well your ipod stops.
    this is how far you can push the official SDK.

    for your app this means: no playback of this "cancellation" signal while playing songs
  5. SkankyToast

    SkankyToast New Member

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    it actually is that hard and yes, I've read the whole posting
    mono or stereo doesn't matter for this task tho
    Why not? sound comes from both sides, so there should be a mic attached to each 'phone.

    The difficult thing is to code an app that can access system level - if an app demands for audio output any other app that was using audio output before is told to stop it...like this:
    you have your ipod playing a song, then you open last.fm and start to play a song - well your ipod stops.
    this is how far you can push the official SDK.
    I was planning on using the dock connector as an input for microphones, and having the "extra" sound interlaced with the output through the headphone jack.

    for your app this means: no playback of this "cancellation" signal while playing songs
    ------------------double post merged------------------
    where might I look to hire a dev to do that?
  6. ZhiZhi778

    ZhiZhi778 Member

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    I got your point

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    the problem is that an app on the appstore can't just "access" any output running through the headphone jack^^
    THAT is the problem

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    interlacing wouldn't work with official tools.

    you need to check around for someone who is willing to develop such an app and who is willing to put it on cydia. best would if he/she already had experience with this process

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    to the stereo or mono thing: of course noise comes from both sides but stereo doesn't mean the same. stereo just tells you it can record two channels at the same time. the important thing though is how you PLACE the mic(s)

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  7. parttimeninja

    parttimeninja Banned

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  8. ZhiZhi778

    ZhiZhi778 Member

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  9. SkankyToast

    SkankyToast New Member

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    What i'm thinking is that the song playing would have nothing to do with the noise canceling app. Can't appstore apps have "music of their own?" as in, sound effects and such that are added overtop of the current playing song from the ipod? I may be mistaken.

    What forum/subforum would you suggest that I look for someone with experience in developing?

    The mics will be placed directly on the outside of each headphone, to be as precise as possible. (breif diagram shown in the headwize project)

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