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VU Meter Ballistics
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VU Meter Ballistics


  • Subject: VU Meter Ballistics
  • From: Uli Zurucker <email@hidden>
  • Date: Fri, 23 Apr 2010 00:20:21 +0200

A VU (Volume Unit) meter is an instrument developed in the 1930's and shouldn't de used these days.

It displayed RMS Level over 300ms. As this won't display peak levels, they dislplayed +4dB more than the actual level. To design, a CARingBiffer and vDSP_rmsqv would be your friends. Do not use this, if you want to design metering for a "pro" application.

Am 22.04.2010 um 21:05 schrieb email@hidden:

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Today's Topics:

  1. Re: iPhone dev- playing sounds defined by the duration of the
     tap (William Stewart)
  2. Anyone have luck matching VU meter ballistics  (mike woodworth)
  3. Re: iPhone dev- playing sounds defined by the duration of the
     tap (Marc Vaillant)


----------------------------------------------------------------------

Message: 1
Date: Wed, 21 Apr 2010 12:45:36 -0700
From: William Stewart <email@hidden>
Subject: Re: iPhone dev- playing sounds defined by the duration of the
   tap
To: Christopher Hansson <email@hidden>
Cc: email@hidden
Message-ID: <email@hidden>
Content-Type: text/plain; charset="us-ascii"

AVAudioPlayer in AVFoundation is what you should be using

You would prepare the players, then when you go to play, the response time should be sufficient for you

On Apr 21, 2010, at 11:54 AM, Christopher Hansson wrote:

Hello,
I have successfully made an app that does -almost- exactly what I want. In a sense I want the UIButtons to trigger like a synthesizer (or sampler, rather), by which the sound file that is played will play for the as long or short as the user holds the button.
How I have it set up now is using AudioServicesPlaySystemSound on the Touch Down event from the buttons. This works great, there is very little/no latency between tapping the button and getting the sound to play. However it triggers the whole sample, and I would like it to stop playing as soon as the user lifts their finger from the button.
Symbiotically, I only want one sound playing at a time.
I have looked through the documentation and have yet to find anything in the SystemSounds that calls Stop or Pause. I have chosen SystemSounds for how quickly it can respond to touches.
I understand there are a couple other frameworks to play sounds, but I've read those induce some latency in calling multiple sound files.
The files I'm working with will be no longer than 4 seconds a piece, CAF format. I am open to using different formats, as well as rewriting my code to get this properly implemented.
Thank you all in advance! I have already learned so much just from reading the subscription.


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------------------------------

Message: 2
Date: Wed, 21 Apr 2010 17:04:53 -0700
From: mike woodworth <email@hidden>
Subject: Anyone have luck matching VU meter ballistics
To: email@hidden
Message-ID: <email@hidden>
Content-Type: text/plain; charset=us-ascii


Hey all,

I'm setting out to write a level meter that closely matches VU meter ballistics, and I'm not finding much via google. Before I break down and buy the IEC spec, I wanted to see if anyone had already reinvented this wheel.

mike
--
Mike Woodworth
email@hidden



------------------------------

Message: 3
Date: Thu, 22 Apr 2010 13:13:16 -0400
From: Marc Vaillant <email@hidden>
Subject: Re: iPhone dev- playing sounds defined by the duration of the
   tap
To: email@hidden
Cc: Christopher Hansson <email@hidden>
Message-ID: <email@hidden>
Content-Type: text/plain; charset=us-ascii

On Apr 21, 2010, at 11:54 AM, Christopher Hansson wrote:


Hello,
I have successfully made an app that does -almost- exactly what I want. In
a sense I want the UIButtons to trigger like a synthesizer (or sampler,
rather), by which the sound file that is played will play for the as long
or short as the user holds the button.

Your best bet will be to use the RemoteIO AudioUnit. You write a
callback function that is continually called by the audiounit to fill a
buffer. The buffer size can be very small, so you can disrupt the
playback will small latency. Please see one of my previous posts where
I have posted some code:
http://lists.apple.com/archives/coreaudio-api/2008/Dec/msg00173.html


If you want to see an app where I use this: http://iditdahtext.com

Best,
Marc
kb1ooo


------------------------------

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