Hi all.

I need to do a rather long recording of sound. The problem is that
the recording device does not have enough internal memory to
support the intended recording in .wav format, so I need to have it
record directly to MP3 format to get the job done.

But then the problem is how to decode the resulting MP3 file.

I need to be able to convert the MP3 file directly to at least one,
preferably several, .wav files without having to keep all the
contents
in memory at the same time. The device that is known to be too
small can handle 2 GBytes of data, the same that my PC can handle.
If I can implement my plan, the MP3 file will be ~1 GByte, and the
decoded .wav data >> 2 GBytes.

Any suggestions?

Rune

Rune:
Not sure about your parameters, but the usual suggestion is to use
"Audacity" - a very popular freeware sound editing package.
http://audacity.sourceforge.net/
Maybe it will do what you want.

Dear Rune!

> I need to be able to convert the MP3 file directly to at least one,
> preferably several, .wav files without having to keep all the
> contents

"lame" is a nice free command line tool, which acts as encoder/decoder for a lot of other CD-ripper, MP3-player, etc.

Kind regards, Jan

Rune Allnor <allnor@tele.ntnu.no> wrote in message <ac4d9a6e-7da1-4cf9-8810-cb44b6ed7232@21g2000yqj.googlegroups.com>...
> Hi all.
> 
> I need to do a rather long recording of sound. The problem is that
> the recording device does not have enough internal memory to
> support the intended recording in .wav format, so I need to have it
> record directly to MP3 format to get the job done.
> 
> But then the problem is how to decode the resulting MP3 file.
> 
> I need to be able to convert the MP3 file directly to at least one,
> preferably several, .wav files without having to keep all the
> contents
> in memory at the same time. The device that is known to be too
> small can handle 2 GBytes of data, the same that my PC can handle.
> If I can implement my plan, the MP3 file will be ~1 GByte, and the
> decoded .wav data >> 2 GBytes.
> 
> Any suggestions?
> 
> Rune

Another vote for "lame".

On 29/01/2010 12:59, ImageAnalyst wrote:
> Rune:
> Not sure about your parameters, but the usual suggestion is to use
> "Audacity" - a very popular freeware sound editing package.
> http://audacity.sourceforge.net/
> Maybe it will do what you want.

It will (though I have never tried it myself with huge files), but you 
have to download and install the LAME library separately (the usual 
licensing issues...); see the plugins page off the above url.  Better 
check CPU loads etc on your device if recording directly to mp3; if it 
goes wrong, it probably goes very wrong.

I am sure you know this, but I will mention it anyway, WAVE has a limit 
of 4GB; some software nevertheless can't cope with >2GB.
Audacity should be OK, as it uses libsndfile.


Richard Dobson.

On 29 Jan, 15:44, Richard Dobson <richarddob...@blueyonder.co.uk>
wrote:
> On 29/01/2010 12:59, ImageAnalyst wrote:
>
> > Rune:
> > Not sure about your parameters, but the usual suggestion is to use
> > "Audacity" - a very popular freeware sound editing package.
> >http://audacity.sourceforge.net/
> > Maybe it will do what you want.
>
> It will (though I have never tried it myself with huge files), but you
> have to download and install the LAME library separately (the usual
> licensing issues...); see the plugins page off the above url. =A0Better
> check CPU loads etc on your device if recording directly to mp3; if it
> goes wrong, it probably goes very wrong.
>
> I am sure you know this, but I will mention it anyway, WAVE has a limit
> of 4GB; some software nevertheless can't cope with >2GB.
> Audacity should be OK, as it uses libsndfile.

It turned out I had misunderstood the data about the recorder.
The thing records to an SD card on either .wav or MP3 format.
The 2GB file size I noticed in the set-up menu was not the
total amount of memory, but the file size when the thing
automatically switches to a new file during recordings.

I bought a 16GB SD card and set the file size to 512 MB, which
ought to get me >25 hrs recoding at 44 kHz and 2x16 bit, even
on raw .wav format.

More than enough.

Rune

Rune Allnor wrote:
> I need to be able to convert the MP3 file directly to at least one,
> preferably several, .wav files without having to keep all the
> contents in memory at the same time.

Most media players have a "disk writer" output, and most MP3 codec
libraries come with a demo program that does just that, convert a MP3
file into a WAV (or headerless raw PCM) file. And unless you insist on
gapless cuts, you can just split the MP3s into arbitrarily sized chunks
before decoding them.


  Stefan