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Sampling Short Sequences From Long MP3 Recordings?
mehl writes "I am a professor for social psychology at the University of Arizona and I am looking for help with finding / developing a special program. In my research, I ask participants to carry around a digital voice recorder while they go about their normal lives. The voice recorder then tracks the ambient sounds in their environments and produces an 'acoustic log' of a person's day. We then use these ambient sound recordings as source data for various person perception studies. For privacy reasons, we are required to sample brief snippets of ambient sounds instead of recording an entire day continuously ('Big Brother is listening to you...'). So far, we have achieved this by modifying the hardware of a digital voice recorder (triggering it with an external microchip). With the high turn-over in player models, however, this strategy has turned out to be short-sighted (every half a year we have to build a new chip). I am thinking about switching strategy, recording continuously in the first place (no problem with the current generation of flash memory) and then sampling (random) snippets after the fact from the continous recordings. Does anybody know of an existing program that can randomly (or pseudo-randomly; e.g., 30 sec every 10 min) and automatically sample short sequences from a day-long (18 hours) mp3 recording? What would it entail to develop such a program (for Windows)?."
I don't know if this is really what you are looking for, but Audacity is what I would look at. Perhaps a custom module could be written to handle random samples.
M
Audacity and a relatively simple plugin. Open source software is good like that.
"It's not your information. It's information about you" - John Ford, Vice President, Equifax
Pick up Microsoft Visual C++ then look at their time and sound librar.. uh.. oh.. IT colour scheme hurt brain... cannot continue.. blarerhfdsl jjjjjjjjjjjjjj fjwkef
Ask P-Diddy.
He frequently samples other artists' work and then makes millions. Reminds me of an archived Onion article, which you now must pay for
Click here for a free picture of an iPod!
Sounds like a job for a really simple shell script driving mp3split. Sounds a lot easier than a custom chip!
If I was a participant in this research I think I would be more concerned with my privacy if they were physically recording everything and then just 'randomly sampling' what they needed later. Having the trigger physically on the player seems much more reassurring. But hey, maybe I'm just paranoid.
Jump to a a random offset, look for the sync-word, copy a number of frames, repeat. The MP3 format is made of frames, there is no per-file header and since the format is designed to be used in streaming applications and to be robust against errors, you can jump right to the middle and grab a couple of frames without worrying about the rest. Many webpages have the frame spec. Here is one.
Perhaps something based off of PyMP3Cut ? I haven't used it, but the description seems pretty relevant ("PyMP3Cut was designed to slice high quality MP3 recordings of day-long congresses into smaller per-speaker MP3 files. It only needs the exact same amount of disk space as the original file to slice, even less if you plan to skip some parts, which PyMP3Cut can do automatically if you use a specially formatted *SKIP* entry in your timeline. It was successfully used many times against several hundredths megabytes MP3 files.").
If you set things up properly (namely limiting the use of the interframe bit reservoir), then there are many utilities which will allow you to pull out specific frames from within an MP3 file. This should both be much faster from a processing standpoint, and not incur more data loss from two encodings.
If they're desperate enough to use your program, they don't have to "40 save a and b to a table". The odds that they'll get the same random number again are lower than the probability that they'll use the program ;).
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make install -not war
MP3 is a bitstream, so you can basically use the language of your choice to seek to arbitrary offsets, slice wherever you like for as long as you like, and whatever frames are broken will simply not get decoded. You may of course want to actually have on-frame-boundry edits (they generally sound better and play more reliably, especially on ipod which doesn't have great stream reassembly code). cutmp3 can work:
- 0. 08/Frame.pm
/ Sp litter.pm
t /p p
:-)
http://www.puchalla-online.de/cutmp3.html
There's lots of pure windows code to do this too:
http://www.programurl.com/software/cutter.htm
But if you want to code this yourself, there's some excellent Perl libraries for managing MP3:
http://search.cpan.org/~nuffin/MPEG-Audio-Frame
(and most directly speaking to what you're working on)
http://search.cpan.org/~ilyaz/MP3-Splitter-0.02
It's not too bad to use Perl either, especially with the Perl Packager. Given only one host with the full Cygwin Perl install, you can create compiled executables that encapsulate everything you need down to a single file. It rocks!
http://search.cpan.org/~autrijus/PAR-0.85/scrip
I imagine though that you'd eventually want to only analyze random chunks that contain speech, or at least speech like frequency distributions. This is trickier, and I don't know if there's Perl code to do it. Maybe you could investigate Praat's internal scripting language?
http://www.fon.hum.uva.nl/praat/
Praat is pretty mind-bogglingly cool -- it's worth checking out no matter what.
--Dan
P.S. Yes, I've been working on some mildly related stuff. How could you tell?
the OP said as much
compare, for example, to the latest (federal) medical privacy rules, www.hhs.gov/ocr/hipaa/
[this sig has been trunca
You ask a person to carry an 18 hour voice recorder... I'm just curious what batteries you use.
Why does this seem absurdly simple to me?
/. isn't the best place, but I think it's great that he's trying to combine a couple of fields of study to develop something new.
It probably probably sounds simple to you because it is. However, this professor said that pyschology was his field, not computer science or programming. I personally think it's great that someone that far out of a tech field has found an useful application for modern technology AND that he decided to check with those most likely to understand the finer details of the techonology. Maybe
Mike Scanlon
Just ask the RIAA. They've got some great software for taking an MP3, extracting bits of the file, and replacing the rest with (loud) white noise. Should be perfect for your needs.
Agreed..
In any case I couldn't imagine that it'd take more than half a day or so to do this in Java or Python.
Or five minutes in Perl with MP3::Splitter:
He is a professor of social psychology not a software developer - give him a break. For an average developer this would be a very simple task - a few days at the most for a simple command line tool or sparse GUI app (Algorithm would be quite simple and all modern languages would support the features you need). You could look for an online forum where developers bid on projects like this for extra money. Usually these sites (Somebody post one I can't remember any of them now but a google search might help you) are very low cost solutions for simple one-off applications like you need. But, since you are part of a University I would contact the CS or IT department and see if there are any Undergrads who would like a small project to make some extra money and/or put on their resume. This would also help solve the problem of setting up your computer to make sure the code works properly (minor configurations would be necessary). Hope all goes well...
Me: In any case I couldn't imagine that it'd take more than half a day or so to do this in Java or Python.
You: perl -MMP3::Splitter -e 'mp3_split($_,{},[ rand(64800), 30 ], ...) for @ARGV' filename.mp3
I would like to take this opportunity to say that Perl guys are smartasses.
James Pennebaker and I developed the method at the University of Texas at Austin at the end of the last century.
Oh you mean FOUR YEARS AGO? Bunghole.
Bad management trumps ideology - Show the world you want better leadership. http://www.timefornewmanagement.com
Use small Windows-based devices and don't give it any further thought. The OS will crash at random (you don't have to pay extra for this, it does it out of the box), thereby giving you the fragmented recordings you seek.
On the other hand, you could do it with an embedded linux device too; the frequent battery changes will have the desirable effect.
Okay I confess I wrote this post to confuse the moderators into inaction; he's bashing windows -- no, he's bashing linux -- oh FUCK what to do...
The correct moderation, gentle mod point merchant, is `funny'.
Blearf. Blearf, I say.
Alright, everybody. Stop posting. It looks like we're done here.
You can't run Open Source code on Windoze without destroying the American way of life!, pinko
I'm not sure that your proposed solution fits with your previously-mentioned privacy concerns. Sure, you'll only see a given part, but you're still recording the whole thing.
It'd be like having the FBI record your calls 24/7, but only listen to them if something came up, or having police be able to raid your house the moment they suspected you, but not look at what they gathered without a warrant. Even if they were completely honest in carrying it out, it's still too Big Brother-ish.
I think that, if the requirements say you can only record brief snippets, then you can only record brief snippets; not record everything and only listen to brief snippets. While it's the same from your perspective, it's not the same in terms of what's actually happening, and it sounds like it's completely bypassing your privacy concerns.
If you're already designing an external microchip, why not design a whole little recorder?
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suwain_2
This is what you want:
mpgedit has a -e flag so you could do
mpgedit -e 1:20-1:30 -e 600:20-601:10 -f file.mp3
Would grab from 1 minute 20 seconds to 1 minute 30 seconds, and from minute 600, 20 seconds to minute 601, 10 seconds of file.mp3 into file_1.mp3 and file_2.mp3
I use it to cut the 2 hour mp3 of the bbc news hours into 5 minute chunks so my mp3 player will let me skip segments.
With a bit of scripting you could do random cuts of any size mp3.
It claims to work under windows, but I have not tested it there.
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Zot O'Connor