Massive Distortion/Digitization

[renaessance]

Greetings!

Sorry for posting this if it's already been addressed elsewhere- but I've looked through the forums and don't quite see this issue.

I'm a relatively new user to Audacity, but I haven't had many problems with it (aside from spontaneous crashing) until now. I have a mult-track podcast I've been putting together, and put the whole thing out on a super-long, 1.5 hour mp3. Well that came out marginally distorted, but when I tried to divide it in half and re-save it (I guess you could say recompress it) into two separte recordings it just sounds -horrible.- Is the multiple mp3 encoding causing fragmented, overcompression, or what?

I reeeeally don't want to have to redo the whole show, as I had many different tracks and many different versions (thanks to the crashing) and it would be a verrry rough (not to mention heartbreaking and frustrating) thing to redo the whole bloody show. (Of which I still can't see how it would be different if I had to redo the entire process.) Could anyone please help? For a sample of what's going on, you can go to http://renaessance.com/Eclectica/Eclect ... enEpP2.mp3

Thanks so Much!
RM

[kozikowski]

Which Audacity? Which Windows?

Multi-track MP3 shouldn't necessarily cause overload distortion which is what that is. Although you are producing a track with up to three trips through the MP3 compressor, and a non Fraunhofer-Gesellschaft MP3 compressor at that.

Where did the song at 17 minutes come from? Ripped CD? That one spends all of it's time in overload clipping.

Koz

[renaessance]

Hiya! Thanks for the reply.

I'm using a relatively slow computer (512 RAM, 996MHz- I know.. oooold.. ) w/Windows XP, and Audacity version 1.2.6. (Tried the latest Beta, but as I was in the middle of this ep. and had so much recorded in 1.2.6, I figgered I'd give that a better go when this ep's done.) I'm afraid that making one large mp3 and then halving that to re-encode the smaller mp3 has over-digitized the file, but I'm not sure how to get around that. Any suggestions would be welcome, and thanks for your help. ^_^

Cheers,
Nae

[renaessance]

PS- I think you're mentioning the vocal track w/the story, and yeah, that'd be the longest track, which was also derived from a ripped CD. (Again, artist permission granted, of course.) I'm relatively new to the advanced audio world though, so I'm not entirely familiar w/the terms you used above. (Sorry, I feel like an eedjit.) But I did just have an idea after doing some serious audio scanning of the track... Could I just re-implant that long vocal track into this new mp3, to help fix the digitization issue?

Gratzi,
Nae

[waxcylinder]

You would be much better off working with WAV files during your production process - and only producing the MP3 file as the final output production file (though I would still keep a copy of the WAV file(s) as well, just in case I needed to do any further editing work later. And do make sure in future that if you are ripping tracks from CD to work on in Audacity , that you rip those as WAVs too.


What Koz is pointing out is that because MP3 compression is a "lossy" compression, some audio is deliberately thrown away (for good) in the compression processs - how much is thrown away depends on the amount of compression you choose by setting the bitrate. The lower the bitrate the smaller the MP3 file - but also the bigger the reduction in quality - it's a trade off. So each time you pass a previously compressed MP3 file throgh the compressor the more audio data it throws away - hence my comment above about working with and storing WAV files.

Koz' other point about LAME not being "Fraunhofer-Gesellschaft": Fraunhofer is the company that owns the patent on MP3 compression , and were Audacity to licence this kosher version they would have to pay Fraunhofer largish sums of money, which is not possible - hence the use of LAME. Koz' comment alludes to the fact that the kosher Fraunhofer MP3s may be better audio quality than those produced by LAME as an Audacity plug-in.

WC

[steve]

Koz' comment alludes to the fact that the kosher Fraunhofer MP3s may be better audio quality than those produced by LAME

Although my own listening experience, and many recent indipendent tests, would indicate that the Fraunhofer encoder is not significantly better or worse than LAME.
For a long time the Fraunhofer encoder was considered to be the "Gold Standard" of MP3 encoding - but there has been no development of it for many years, during which time LAME has done a lot of catching up (some say surpassing).