Cycling 74 » Topic: Keep a running average of the last N samples http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/feed Tue, 18 Jun 2013 15:26:06 +0000 http://bbpress.org/?v=2.2.4 http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/#post-47233 <![CDATA[Keep a running average of the last N samples]]> http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/#post-47233 Wed, 16 Dec 2009 18:34:49 +0000 willyc Hello,

I want to keep a running average of the last N samples (or X milliseconds) of an audio stream. The patch below demonstrates exactly what I’d like to do in Max terms, but I can’t seem to make a satisfactory solution with MSP objects. There is a proposed solution using [+=~] but as indicated in the patch it is not without creating a potential problem….

Any ideas or externals that might help? I want to remain entirely in the signal domain if possible….

Cheers
Will

– Pasted Max Patch, click to expand. –

]]> http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/#post-169868 <![CDATA[Re: Keep a running average of the last N samples]]> http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/#post-169868 Wed, 16 Dec 2009 18:59:57 +0000 Tim Lloyd Maybe you’ve already tried this and it isn’t quite what you mean, but couldn’t you just adjust the interval time of the average~ object? It’s default mode with an argument of 44100 seems to do the same thing as your example patch.

]]> http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/#post-169869 <![CDATA[Re: Keep a running average of the last N samples]]> http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/#post-169869 Wed, 16 Dec 2009 19:30:24 +0000 willyc That would only provide the average amplitude (of the previous seconds audio) once a second.

I want to know the average of the last X ms of audio every single sample….

]]> http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/#post-169870 <![CDATA[Re: Keep a running average of the last N samples]]> http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/#post-169870 Wed, 16 Dec 2009 21:01:15 +0000 MIB I haven’t used it personally, but there is an object out there (ircam??) called [accumulate~]. it might do what you need or at least get you closer…

]]> http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/#post-169871 <![CDATA[Re: Keep a running average of the last N samples]]> http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/#post-169871 Wed, 16 Dec 2009 21:29:06 +0000 Tim Lloyd I think you’re referring to the CNMAT accumulate~ object, which very similar to the new +=~. It still has the 32-bit float accuracy limitation that +=~ has, so after about 6 mins at 44100sr, your patch would become inaccurate.

I do get what you’re saying that you need now, but I’m not sure how to go about doing it.

]]> http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/#post-169872 <![CDATA[Re: Keep a running average of the last N samples]]> http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/#post-169872 Wed, 16 Dec 2009 21:30:55 +0000 ComfortableInClouds actually, average~ does exactly what you are looking for. That is, the oldest value leaves the buffer as the newest sample value enters and then the average is recalculated, at every single sample. Thus giving a continuously updated average value. what you described is the avg~ object, not average~.

Using the CNMAT accumulate~ external, you can create a memoryless system to analyze the instantaneous energy in a signal. Look at the leaky-integrator example provided in the accumulate~ help file if you’re interested.

]]> http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/#post-169873 <![CDATA[Re: Keep a running average of the last N samples]]> http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/#post-169873 Wed, 16 Dec 2009 21:40:48 +0000 Tim Lloyd I nearly suggested that example, but couldn’t think how to go about changing the number of samples that the integrator “averages” over.

]]> http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/#post-169874 <![CDATA[Re: Keep a running average of the last N samples]]> http://cycling74.com/forums/topic/keep-a-running-average-of-the-last-n-samples/#post-169874 Thu, 17 Dec 2009 12:31:20 +0000 willyc Thanks for all the suggestions. It looks like [average~] actually does exactly what I want.

Looking at the helpfile for it reveals it produces a signal output. The reference manual states a float output, hence my initial reluctance in using it. Cheers

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