Hi I’m using the 2.0.2 version of Audacity with the Windows 7 OS.
Can someone tell me why, when I import an audio file from my desktop into audacity, there are red vertical lines throughout the track, nearly covering the blue waveforms?
Any help would be greatly appreciated!
Red vertical lines appear as a warning that the audio is touching 0 dB (top/bottom of the track).
Digital audio cannot (normally) go beyond 0 dB, so if the signal touches the top or bottom of the track it could be an indication that the recording is “clipped” (distorted due to the recording being at an excessively high level).
You can turn off the warning lines: deselect “View menu > Show Clipping”.
an audio file from my desktop into audacity,
So the desktop created a sound file that was too loud.
If you used Audacity on the desktop, you can turn on clipping indicator and probably see the red lines there, too. View > Show Clipping.
There is one oddity. If you have a dense, loud WAV or high quality show on the desktop it could be OK, and you can get the damage when you export an MP3. MP3 compression can change the blue waves. Creating small music files isn’t free.
Never do production in MP3.
This can be a bit confusing… There might not be anything “wrong” with your file, and if you didn’t create the file yourself, there’s nothing you can do about it anyway.* If the file is clipped (has flat-topped distorted waves) and you reduce the volume (by using Amplify or Normalize), the red will go away and Audacity won’t see a problem, but the wave shape won’t change and you’ll still have clipped/distorted waveforms.
If you create or edit the file yourself, you should try to avoid clipping. For example, if you boost the bass on a file and you see red, you should reduce the volume before saving. Audacity (and most audio editors) use floating-point internally, so there is no upper limit… You’ll see red as a warning, but the waveform won’t actually be clipped… yet. But, if you save (export) a file that goes over 0dB, it may end-up clipped and that’s “bad practice”.
Regular (integer) WAV files simply cannot go over 0dB. Many modern CDs have peaks that hit exactly 0dBFS, and these will show-up as red. If the song is highly compressed, you’ll see lots of red. MP3 files can ligitimately go over 0dB (without clipping). However, if you play the MP3 file at full volume you can get distortion, since your digital-to-analog converter cannot go over 0dB.
The higher than 0dB peaks in an MP3 are usually caused by the lossy compression process… During compression, the wave shape changes and some peaks get higher and some get lower. (As far as I know, the clipping caused by lossy compression is always slight and is never audible… If/when people hear MP3 compression artifacts, they are hearing something else.)
- Audacity has a Clip Fix “effect”, and there are other clip repair tools. However, these tools are not perfect. When a waveform is clipped, the information is permanently lost and there is just no way to know the original height and shape of the waveform.
Thanks for your help guys much appreciated, I think I’ll just try and get rid of those red lines for now!