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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)?."
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.
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.
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
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...
Which gives the CS student experience to put on his/her resume, and helps forward the research of the non-coder academic.
snip four line shell script that pretty much (except converting to mp3 format) accomplishes what is desired by submitter
What amazes me is that this precisely the sort of thing to do in software, yet the submitter contends that up until now they've done it with a custom designed and custom built chip.
I mean, the guys at http://rockbox.haxx.se could do it in about 15 minutes, and provide a GUI on the MP3 recorder.
Naturally, this is easier to do when MP3 recorders are running open source software, so to an extent this is a rant at all the manufacturers of computing appliances who see a competive advantage in closed source: you lost my purchase, and who knows how many purchases from this professor and while requiring him to shell out even more for a custom chip to do in hardware what is ridiculously easy to do in software (as the parent poster shows by using that complex and little-known software technique, calling sleep()).
I'm not criticizing the parent: his code does the right and the simplest thing; the problem is with manufacturers whose use of closed source precludes such elegantly simple solutions.
A big part of the reason that the IBM PC took off in such a big way in the early 1980s was becuase it was open source: not the code to MS-DOS, but the architechtural specification of the hardware itself. This cost IBM money when "clone"-makers were able to produce "monkey copies" of the PC, but that very competetion made PCs much more popular, and soon dominant over other (possivly techically superior) brands like Ape or Amiga. The open specs also allowed a myriad of other companies to offer add-on hardware from co-processors to graphics cards, and even allowed software authors to optimize for the IBM-PC (who here is old enough to remember what peripheral's memory was mapped to address B800, and the advantages to manipulating the data there directly?)
Did opening the IBM-PCs architecture finally cost or benefit IBM. We'll never know. But it is likely that the PC market, and thus the market for home PCs and peripherals, and software for home PCs and the World Wide Web, would never have been near as big without IBM's decision to open the PC even to competitors.
Manufacturers of closed-source appliances would do well to consider what they gain, and what they lose by preventing customers from fully using their products. (The careful reader will see that the antecedent of "their" in the previous sentence is ambiguous; the astute reader will understand why: just whose product is it, the company that makes it or the customer who buys it?)
Opinions on the Twiddler2 hand-held keyboard?
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