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resu
- Posts: 1
- Joined: Sat Dec 17, 2011 3:46 pm
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by resu » Sat Dec 17, 2011 4:12 pm
whenever i import music from my library into Audacity, the levels seem to be increased, leaving the waveform covered in anything from just a few to a plethora of red clipping lines
the music is most definitely mastered at a 0.0 dB limit, as much of it comprehends mp3s i've bought from beatport, or personal CD rips
it's a waste of time having to normalize every single track imported, and even then i will, in many cases, be left with a few stagnant lines, that have to be remedied manually
it's really slowing down the efficiency of my efforts, especially when workin on multiple files...
i've tested this with both mp3 files and a couple of wavs, going from version 1.2.6, to 1.3.13, and finally 1.3.14, results being all the same in every case...
is it possible prevent this import levelling from happening, or could it be a bug ?
Windows XP Pro SP3
Realtek AC97 Audio (latest driver)
DirectX 9.0c
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steve
- Site Admin
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by steve » Sat Dec 17, 2011 4:49 pm
It's not a bug, it's a feature of the MP3 format.
MP3 is a "lossy" compressed format. In order to reduce the file size, some audio data is discarded and the MP3 is an approximation of the original audio data.
If the audio data is normalized to 0 dB before encoding, then it is very common for the MP3 encoded file to show a lot of clipping as in your screenshot. The only way to avoid this problem with MP3 encoding is for the audio to be normalized below 0 dB before encoding so as to allow sufficient headroom so that the encoded audio does not clip. A better solution (from a sound quality perspective) is to use lossless formats such as WAV, AIFF or FLAC rather than MP3, but this has the disadvantage that the file size will be very much bigger.
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Gale Andrews
- Quality Assurance
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- Operating System: Windows 10
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by Gale Andrews » Sun Dec 18, 2011 12:10 am
It should happen less if you use a higher MP3 export bit rate (in the "Options" button when you export).
As you are using the default 32-bit resolution for projects, you can undo the MP3 clipping by using Effect > Amplify - it should show a negative value in "Amplification (dB)" which is the value required to bring back the New Peak Amplitude to 0.0 dB. You want to set the New Peak Amplitude a bit lower to -1 dB or -2 dB to avoid clipping.
It isn't possible to repair an imported WAV in this way unless it's a 32-bit float WAV.
Gale
