mp3 distortions

[mathc]

I have used Audacity 1.25 for a long time to edit our church's service each week. It is recorded via Tascam recorder onto a CD. I take it home, choose the tracks I need, import them into Audacity, do the editing needed on each track, string them together with an intro and closing, then export it as an mp3 file using the LAME plug-in before podcasting. Everything has worked well until I downloaded the newest version of Audacity, 1.3.13. I set up the preferences with exactly the same values as I had in version 1.25 and made sure that LAME had the same bit rate, but when I listened to the result in iTunes, the voices were all distorted. It sounded like the speakers each had their heads in a bucket with swirling water in it. The settings that I used for both Audacity 1.25 and 1.3.13 were
Sample Rate: 44100 Hz
Sample Format: 32-bit float
MP3 library version: LAME 3.98.2
Bit Rate: 48
I tried adjusting the sample format and the bit rate various ways but they gave me a file size that was at least twice as large in each case.
I am working on an iMac OS 10.5.8
Help!!

[kozikowski]

You should be in Audacity 1.3. 1.2 is becoming more and more unstable on modern computers and is no longer supported.

48 is barely enough for a mono show, but will destroy a stereo show. Did you mix down to mono and export that? That should sound passable. Audacity 1.3 has a Track tool that will mix down for you.

I don't trust 32-float. There have been reports of damaged MP3 files from that. I would be capturing the show at 16-bit and export that, but you can experiment.

Koz

[kozikowski]

You said you adjusted MP3 export in preferences. Audacity 1.3 adjusts MP3 export at the actual Export step. Did you mis-speak? Also, Audacity 1.3 default export is 128 which should give you a very nice presentation, just way too big.

Koz

[mathc]

I know that I can get a cleaner audio sound by using a variable bit rate in version 1.3.13 regardless of whether I use 32 bit float or 16 bit. But the file size becomes too large for a podcast. Regarding the adjustments, I adjusted version 1.25 in the preferences and 1.3.13 at the export step. Since I posted this, I have made further tests and it seems that when the volume was a bit too low in a section and I amplified that section that it really magnified the problem. Version 1.25 with bit rate of 48 handled the amplification just fine with no distortion regardless of whether I set it at 32 bit float or 16 bits. But version 1.3.13 couldn't handle the amplification at 48. But managed better with a variable bit rate at level 9. But even at that minimal level, the file size was half again as large as it was with 48. If I had short programs, file size wouldn't matter so much and I would raise the bit rate a little for a better sound. But a podcast an hour long is hard enough to download with the file size made as small as possible when the listener is in a less well to do country. I'm trying to keep them in mind. 80% of our subscribers live in China. Others live in African countries and various islands. To answer your question about mixing it down to mono. I have read that podcasts need to be in stereo because some players don't handle mono. So, no, I haven't mixed it down to mono. Thanks for your help.

[kozikowski]

I'm out of ideas. It's really scary when the example system didn't work right. That is, it did exactly what you wanted, but it was broken. Now you're trying to get a properly working system to replicate the old software and none of the results work as you want.

Traditionally, you couldn't force a stereo show at 32 to sound acceptable. It was seriously distorted. 64 was the absolute minimum. So you're somewhere in the middle. That's generally accepted as normal -- and it does it in multiple different audio programs. I did my initial experiments in Cool Edit and my boss had similar results using a different program. Audacity is following right along.

Let's see what the other elves have to say.

Just a note that "lame" is also a stand-alone software program -- not just a plugin -- and I think you can get a version to work under OS-X.

Koz

[kozikowski]

http://www.macupdate.com/app/mac/18882/lame

It's a command-line program, so you have to be comfortable in Mac Terminal.

Koz