I have imported backing tracks. Some have red vertical lines on the time line/ may be 2 or 15 spaced irregularly.
They don’t seem to effect the replay sound. What do they indicate? Other tracks have none !
Thanks Mike40 Melbourne Aust.
Post by steve » Thu Jan 03, 2013 10:57 am
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”.
The red lines indicate the sound at that tiny instant got too loud or close to being too loud. If you can’t hear any damage, cracking, clicking, ticking or harsh noises, it’s probably OK.
If your show has a lot of red lines…
That’s probably serious sound damage.
I’m using a lot of fuzzy words there because we can’t actually measure sound that got louder than maximum. The best we can do is compare what you have to natural sounds and raise an alarm if the two are different.
Electronic music can drive this system nuts. No natural sound.
Koz
I am getting a red clipping line now and then when I amplify in Audacity a 32-bit float WAV recording. Should that be happening?
Thanks.
I keep re-reading your question and I still don’t understand what you are asking.
I am getting a red clipping line now and then when I amplify in Audacity a 32-bit float WAV recording. Should that be happening?
Audacity shows red for potential clipping. It’s just checking the peak level. You can get false positives and false negatives…
Analog-to-digital converters (recording), digital-to-analog converters (playback), and regular (integer) WAV files and audio CDs are all hard-limited to 0dB and they will clip if you “try” to go over.
If you see red immediately after recording you clipped your analog-to-digital converter. If you then lower the volume with the Amplify effect, the peaks will no longer hit 0dB so Audacity will no longer show red, but the waveform is still clipped.
If you have a good-unclipped file and you Amplify, or boost the bass or something pushing the peaks go over 0dB, Audacity will show red but since Audacity uses floating-point it’s not actually clipped… yet. If you play the file at “full digital volume” you’ll clip the digital-to-analog converter, or if you export as regular WAV, the file will be clipped. But if you can reduce the volume before exporting everything will be OK.
MP3s can go over 0dB without clipping and many “ripped” MP3s will show red. Usually this is a result of the lossy encoding which changes the waveshape making some peaks higher and some lower. Again, you will clip your digital-to-analog converter if you play it at “full digital volume”. But as far as I know this slight clipping is not audible. It’s not something I worry about. MP3 is lossy anyway and if you hear a compression artifact you are probably hearing something else and lowering the volume before MP3 compression probably won’t fix it.
Thanks, DVDdoug. Potential clipping or a clipping warning makes sense. One day I will finally trust my ears.