[R] Limitations of audio processing in R

[(Ted Harding)]

Hi Ulisses!
Yes, "get more creative" -- or "get more memory"!

On the "creative" side, it may be worth thinking about
using an independent (non-R) audio file editor. I'm
writing from the standpoint of a Linux/Unixoid user
here -- I wouldn;t know how to set ebout this in WIndows.

You could use R to create a shell script which would run
the editor in such a way as to extract your 6 random samples,
and save them, where the script would be fed with the
randomly-chosen 5-minute intervals decided by R. This
could be done under the control of R, so you could set
it up for your 1500 or so sets of samples, which (with
the right editing program) could be done quite quickly.

On Linux (also available for Windows) a flexible audio
editor is 'sox' -- see:

  http://en.wikipedia.org/wiki/SoX

To take, say, a 5-minute sample starting at 1 hour,
10 min and 35sec into the audio file "infile.wav",
and save this as "outfile.wav", you can execute

  sox infile.wav outfile.wav trim 01:10:35 00:05:00 

and such a command could easily be generated by R and
fed to a shell script (or simply executed from R by
using the system() command). My test just now with
a 5-minute long sample from a .wav file was completed
in about 5 seconds, so it is quite efficient.

There is a huge number of options for 'sox', allowing
you to manipulate almost any aspect of the editing.

Hoping this helps,
Ted.


On 21-Sep-11 19:55:22, R. Michael Weylandt wrote:
> If you are running Windows it may be as simple as using
> memory.limit() to allow R more memory -- if you are on
> another OS, it may be possible to get the needed memory
> by deleting various things in your workspace and running
> gc()
> 
> Of course, if your computer's memory is <3GB, you are
> probably going to have trouble with R's keeping all objects
> in memory and will have to get more creative.
> 
> Michael
> 
> On Wed, Sep 21, 2011 at 3:43 PM, Ulisses.Camargo <
> moliterno.camargo at gmail.com> wrote:
> 
>> Hello everybody
>>
>> I am trying to process audio files in R and had some problems
>> with files size. I´m using R packages 'audio' and 'sound'.
>> I´m trying a really simple thing and it is working well with
>> small sized .wav files. When I try to open huge audio files
>> I received this error message: "cannot allocate vector of
>> size 2.7 Gb". My job is open in R a 3-hour .wav file, make six
>> 5-minute random audio subsamples, and than save these new files.
>> I have to do the same process +1500 times. My problems is not
>> in build the function to do the job, but in oppening the 3-hour
>> files. Does anybody knows how to handle big audio files in R?
>> Another package that allows me to do this work? I believe
>> this is a really simple thing, but I really don´t know what
>> to do to solve that memory problem.
>>
>> Thank you very much for your answers,
>> all the best!
>>
>> Ulisses

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Date: 21-Sep-11                                       Time: 22:05:55
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