I have been downloading audiobooks from my library system and listening to them on a Karma and an iPod. The sound quality is, uhhhh, less than desirable. This is not surprising when you consider that the original files are 32KBPS WMA files, transcoded to MP3s. The sound quality problems are the all too familiar "echo in a tin can" sound at the higher frequencies, particularly with a female narrator.

Is there software that will crudely and quickly equalize a batch of MP3 files, just stripping out everything above, oh, say, 3000 Hz? I am not looking to achieve authentic or natural sound, or even sound that would be considered good. If I could reach the status of "not annoying" that would be fine. FWIW, setting the iPod's minimal EQ characteristics to "Treble Reducer" helped. But not enough.

tanstaafl.

I think you can do large scale batch processing work in CoolEdit, and it can do equalization like you say.

Not sure you'd be *happy* with the results; I'd do some test myself on a single file first. If a simple brick wall filter at 3k solved sound-quality problems on low bitrate MP3s, you'd think they'd just build that into the encoder.

(Actually, they do build that into some encoders come to think of it, but it's at a much higher frequency.)

Oh, and, remember that, since your source file (the one you wanna filter) is *already* an MP3 file, it means that it's gonna need to be re-encoded *yet again* after it's been filtered, adding yet another layer of data compression artifacts...

Hi,

I use Magix Audio Cleaning Lab.

It has a lot of tools to help with this and other problems. What might help you is to decompress, then equalize, de-noise at a low threshold, and re-encode.

Ross

Not an option, unfortunately. My original source files are 32KBPS *.WMA files, already highly compressed, so the damage is pretty well done before I ever start. I think the original *.WMA files do sound better than the transcoded, DRM-removed MP3 files I end up with, but the iPod doesn't play *.WMAs. At least, I don't think it does. Does it?

tanstaafl.

Nope. Apple hasn't supported a proprietary Microsoft format yet. iTunes on Windows will read WMA just by using the built in support, but to play them on an iPod, they need to be converted.

Hey. Here's something I'm wondering.

When you are transcoding these files from WMA to MP3, are you trying to do the new file at the exact same bit rate as the old file?

In other words, if you started with a 32kbps WMA file, are you trying to make a 32kbps MP3 file?

If so, there's your problem. Just bump the bit rate of the MP3s up when you're doing the transcoding: Go up to 96 or 128 or something, and that will help prevent a large amount of artifacting that's generated by the second re-encode.

It won't remove the artifacts that already existed on the source files, but at least you won't be adding too much in the way of additional artifacts as part of the re-encoding process.

What's the sample rate of the original WMAs? If it's 8KHz, make sure you're also creating MP3s at 8KHz. That in itself will wipe out anything above 4000 Hz.

Peter

I'm using the transcode options provided by Tunebite, which are optimized for audiobooks and they do sound better than any parameters I tried on my own. Tunebite uses pre-packaged paramter sets, and my next best choice ends up at 192 KBPS VBR, and for some reason even though it is supposedly VBR, the files end up at a full 192 KBPS average.

tanstaafl.

I'll definitely look into that. My encoding options with Tunebite are limited, though. It uses LAME, but does not give me access to command-line parameters, I have to use their "packages".

tanstaafl.