Arnold Kling  

mp3's and lectures

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Tyler Cowen asks,


Why don't econ bloggers post their classroom and public lectures?

I already do. I add one or two per week. The latest one includes an interactive quiz.

I record them using an Olympus DS330 digital voice recorder. The files are very small in their proprietary format, but that format is otherwise user-hostile, so I convert the files to MP3's, which tend to be 3 or 4 times larger.

For Discussion. Does anyone know of software that converts .wav to .mp3 files that produces really small .mp3 files?


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CATEGORIES: Economic Education



COMMENTS (8 to date)
Bluehoo writes:

There are lot's, but I use iTunes. If you encode in mono at 16 kbs, which I do for some talk radio programs, an hour's worth is around 7 MB.

max writes:

You might try lame, if the licensing is not an issue. http://lame.sourceforge.net/using.html

Something like: lame -b 32 infile.wav outfile.mp3 will result in a quite small mp3. See
http://lame.sourceforge.net/USAGE for more info about various options. Size is of course traded for quality.

Bernard Yomtov writes:

Hey. I got all eight right.

ARnold Kling writes:
Something like: lame -b 32 infile.wav outfile.mp3 will result in a quite small mp3.

As usual, I find open-source based software hard to figure out. The best I could do with one LAME-based tool I downloaded was slightly worse than what I could do with something called Coffee Cup rip-and-burn. That is, the file was slightly larger with the open source stuff. But I have no idea how to optimize the open source stuff.

I think that if one could set the bitrate rate from 32 k down to 8 k it might help. But I don't know how to do that, and it's just a guess, anyway.

Guillaume Lessard writes:

You should reduce the sampling rate to 12 kHz in order to get small file sizes. In doing so, you remove all frequencies above 6 kHz, which will not adversely affect the intelligibility of the recording; on the other hand, it will make high-frequency artifacts from the Olympus files less obvious. Using LAME, the following is pretty good for spoken recordings:

lame --resample 12 -b 24 -m m

That'll be a mono file at 24 kbps.

Cary Lewis writes:

There are several good solutions for low bit-rate audio. A recent test of them was summarized at the following site: http://www.rjamorim.com/test/32kbps/results.html

Most of them are problematic at very low rates, not least because they would require your users to download new software to listen. If you assume they have iTunes, the AAC seems like a good bet.

The program dbpoweramp can make it easier to convert audio formats than some others. It can be used with the aforementioned LAME as well as many other codecs.

Arnold Kling writes:

"Most of them are problematic at very low rates, not least because they would require your users to download new software to listen."

That's what's true of the dss format in which I make the recordings. You have to download the software, and on top of that the browser tries to read the format as an HTML page, so you have to save the file to disk and then listen to it. That's what I mean by being a user-hostile format.

Chris writes:

I tried re-encoding one of your MP3 files as 8 kbps mono AAC using iTunes and I got a pretty decent quality at 1/4th the size. You might want to try that.

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