In an earlier thread it was mentioned that CDex can be used to convert .wav files to .mp3 and give relatively small file sizes. I'm thinking the numbers were something like 40 minutes held in 10 MB of disk storage. I'm using CDex - as well as Audacity and a couple other conversion tools - and I'm gettin much closer to 1MB per minute recorded - maybe 4 times the file size mentioned. Can someone getting smaller file sizes please post CDex settings being used? Or other trick to keep things smaller?

David,

We use Audacity to work with our audio files and then produce the MP3 files for the website. On average I would say our files are approx 10MB for 40 mins. The settings in Audacity we use are:
Quality - Default Sample Rate: 22050Hz
File Format - MP3 Export Setup - Bit Rate: 32

I hope this helps,

Sandy

David,

I'm the culprit who suggested CDex actually. ;) CDex Screenshot

I've had to tinker with this a good deal recently, as the local church I'm employed at had to rework their encoding strategy. (Long story) The above image are the settings we're using currently. They're not too off from what Sandy has posted on.

David,

As a reminder, file size is totally a function of bite rate and duration. It does not matter what software you use to encode it. The thing that will vary for different encoders is quality. Here is how the calculation goes for a 40 minute MP3 encoded at 32 KB/Sec:

40 minute * 60 seconds/minute * 32 Kbits/second * 1 byte/8 bits = 9600KB = 9.6 MB

As a rule of thumb, divide the number of minutes by 4 to get the size in MB. To be more exact, multiple it by 0.24. So 40 * 0.24 = 9.6 MB

In Him,
Mark

Thanks, Samdy, Brian, and Mark. Those settings do get me much closer. A 24-minute sermon is generating a 13.9MB file. I have bitrate set at 32, max 40. (What's the significance of the max bitrate?)

David,

Bitrate itself goes back to what Mark explained, and is the biggest factor in the size of the file. Max and min bitrates in this context are settings for VBR encoding (Variable Bit Rate), as opposed to CBR (Constant Bit Rate).

With VBR the encoder changes the bitrate on the fly, effectively saving as much space as it can (like during silence,) but still reproducing the important sounds as naturally as possible. The Max Bitrate setting specifies the maximum amount of kbits per second it should try to use to reproduce the sound. "Don't use any more than 40kb/s to encode the sound." Thus the encoder is trying to figure out which sounds are important and the optimal data rate, up to the maximum, to use for that.

If you were using CBR, the encoder always uses x kbits/second to encode the sound. This is higher quality, but produces a bigger file.

That's my interpretation anyway. ;) Maybe I left some detail out.

David,
I use razorlame which uses the same mp3 encoder as Audacity but is more configurable. My settings -b 32 -a --resample 22.05 (mono 22mhz sample rate 32kps)
create a file small enough (9mb) in this format (30-40 min message) that plays at the right speed in the WEC flash player.

download razorlame here http://www.dors.de/razorlame/download.php

Hope this helps
Andre

Brian, thanks for the VBR explanation. I at least have a clue now what's going on.

Andre, your settings got me down to 8.3 MB - a big improvement over what I've been getting. And razorlame worked just fine, although I think I should be able to get the same result with Audacity or CDex, since they're all just using LAME. Thank you.

I still haven't reached the 4:1 target. I'm wondering if my version of LAME might be the issue - although I'm just one tick short of current. Anybody know if 3.97 brings better compression than 3.96?

The problem with Audacity is that you can't set the LAME settings as finely as you can with RazorLAME. Tha tis why I switched for may conversion. I don't know CDex so I can't comment on that.

Andre

I have a same problem. Sometimes the sermon was 50-60 minutes. How can I extend 10MB to 20 MB for mp3 file.