Editing a stereo mp3 file

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Editing a stereo mp3 file

Post by DR CHICK » Thu Oct 12, 2017 2:44 am

I am using Audacity 2.1.1 on a computer with Windows XP. I think my Audacity used a .exe installer.
I have a bad transient in my stereo mp3 recording caused a bouncy stylus on my LP turntable. I have tried a HPfilter but that hasn't been successful yet. If that part works I still have to remove a initial jump. My next approach will be to copy the section with the transient to another track. Remove the audio with a LP filter and invert the results. Next add the processed section back to original section. The transient is about 0.4 seconds long so repair or pencil are not feasible. My problem is understanding the steps of copying the transient section and then adding the modified results back to the original track. Thanks for any help. DR CHICK.

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Re: Editing a stereo mp3 file

Post by steve » Thu Oct 12, 2017 11:08 am

Please post a short audio sample in WAV format (see: viewtopic.php?f=49&t=72887)
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)

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Re: Editing a stereo mp3 file

Post by DVDdoug » Thu Oct 12, 2017 4:45 pm

caused a bouncy stylus on my LP turntable.
I don't understand what you mean, but is that something you can avoid by recording again?

Have you considered looking for a digital version of the song? If the defect is really bothering you, it's probably worth spending a dollar on Amazon or iTunes. Or if it's not available digitally and the defect is on your record, maybe you can find another vinyl copy.

There are some special-purpose tools for fixing-up digitized vinyl recordings, but they are generally for shorter-duration "clicks" & "pops". I use Wave Repair ($30 USD) and Wave Corrector (now FREE). Wave Repair has an option where the defect is replace by the surrounding spectrum (similar sound) and sometimes that works very well, but there is a selection-time limit and 0.4 seconds might be too long. It also has an option of replacing the defect with a similar-sound, but I haven't had much luck with that. Of course, you can do that in audacity too but with either application it's hard to get the timing just-right.

in my stereo mp3...
Let's talk about MP3 for a moment... MP3 is lossy compression. It's NOT terrible, (it's better than analog vinyl) and a high quality (high bitrate) MP3 can often sound identical to the uncompressed original in a scientific, blind, listening test. But it is lossy, and it shouldn't be used for audio production & editing (unless you're stuck with an MP3 original and you have no choice). If you want MP3, compress to MP3 ONCE as the LAST step.

Audacity (like all "normal" audio editors") works on uncompressed audio, which means when you load an MP3 it gets decompressed. If you then re-export to MP3 you are going through another generation of lossy compression, and the "damage" does accumulate.

And since MP3 changes the wave shape and, it can make vinyl cleanup applications less effective. (Actually, Wave Repair only works with WAV files so you'd have to manually convert to WAV if you want to try/use that application.)

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