Show Clipping in Audacity

[IanR]

Note: I've moved this discussion to the Home Recording/General board so that it doesn't detract from the original topic which can be found here:

https://songcrafters.org/community/index.php?topic=17973.0

- 64Guitars

Nice job, Ian. Well played and the vocals sound great - both the lead vocal and The Supremes.

There's a fair bit of clipping but otherwise the recording is great. The mix is very good. You just need to watch those levels. I recommend checking your mix in Audacity after mastering to see if there's any clipping, as shown in my tutorial here:

https://songcrafters.org/community/index.php?action=articles;sa=view;article=15

If Audacity shows a lot of clipping, then you should remaster on the BR with a slightly lower recording level.

Thanks 64 Guitars.  I actually had a print out of your tutorial next to me as I processed the WAV files in Audacity.  I normalised the tracks and trimmed the front end and converted it into an mp3 exactly as you described.  The normalised tracks did not show any clipping.  There was none there, even before I normalised.

Therefore, I probably recorded the original tracks too loud.  I'm still getting used to the recording level in the BR800.  

I will try to re-master the original tracks to see if it helps.  I think the bass in the mix that I posted is way too loud anyway.  And I have to include a better drum track and some lead guitar.  Hopefully by the end of this week.  I've said it before - there's a lot you have to know and do to be a good "home recorder".

Thanks for the tips,

best regards,

Ian

[64Guitars]

I normalised the tracks and trimmed the front end and converted it into an mp3 exactly as you described.  The normalised tracks did not show any clipping.  There was none there, even before I normalised.

Here's how your MP3 looks in Audacity:



A few possible explanations come to mind:

1) Maybe you forgot to turn on the "Show Clipping" feature in Audacity. Notice the checkmark in the View menu in the screenshot above. That indicates that the feature is enabled. If there's no checkmark, then the feature is disabled and you won't see any red lines, even if the recording has lots of clipping.

2) When you set the Normalization Maximum Amplitude to -0.1 dB as per my instructions, you might have forgotten the minus sign. In that case, it would normalize the song to +0.1 dB, which would cause clipping where there was none before. Although, I just tried that in Audacity 2.0.0 and it wouldn't even accept positive values. The OK button was disabled until I entered a negative value. But I'm running under Linux. Perhaps the Windows version behaves differently.

3) Perhaps the track level control was not at 0. If it's higher than 0, you'll get clipping even though you normalized the track before exporting. If you double-click on the track level control, a Gain window will pop up where you can view and edit the exact level value. If it's not 0, then just type a 0 and click OK.

Therefore, I probably recorded the original tracks too loud.  I'm still getting used to the recording level in the BR800.

If you set the track levels too high while recording, then those tracks will have clipping. But it won't show in Audacity if your overall level is set correctly. The red lines in Audacity indicate samples in the final recording that hit or exceed 0 dB (the maximum value a sample can store). So the screenshot above shows that your levels reached or exceeded 0 dB at the time you exported the file. They may have also reached or exceeded 0 dB on some of the individual tracks, but there's no way to tell that by looking at the final mix in Audacity, unless you zoomed in really close on the waveform and saw a lot of square waves where there shouldn't be any.

[IanR]

Thanks 64 Guitars

I'm looking forward to checking your suggestions.

I'll import the individual tracks into Audacity and see what shape they are in.

I had no idea that I had to turn on the "clipping" view.

And you may be right about the setting I used when normalising.

Ian

[IanR]

64 Guitars,

I just checked my Audacity files

Here is what the track look like after I finished following the 64G tutorial (Audacity.jpg)



And this is what the mp3 looks like (Audacity2.jpg)



"Show clipping" is switched on in both views.

I can hear clipping when I play back the tracks through Audacity but I can't get it to show up.

Ian

[64Guitars]

Is that after normalization? You won't see any clipping after normalization because normalization ensures that none of the peaks exceed the value you specify, which is always less than 0 dB. However, if the waveform was clipped before normalization, then it will still be clipped after normalization. You just won't be able to see it because the level has been reduced by normalization. That's why, in my tutorial, the very first thing I said to do is check for clipping, right when you first import the WAV file from your BR. If you see clipping at that point, there's nothing you can do about it in Audacity. You have to go back to the BR and remaster at a slightly lower level. The purpose of normalization is to boost levels when they're a bit too low. It can't help if the levels are too high. It doesn't change the waveform, it only changes the level. So, if the waveform is already clipped, then it will still be clipped after normalization but you won't see any red lines because the level has been reduced.

Here's a section of your MP3 where I've zoomed in real close so we can see the individual samples (the blue dots).



Notice the section roughly between 0.0010 and 0.0020. All of the samples in the left channel are hitting the ceiling (0dB, or 1.0 on the scale to the left) so they form a straight horizontal line. That's clipping.

Here's what the same section looks like after normalizing. I set the maximum amplitude to -3.0 to exagerate the effect visually. You wouldn't normally use such a high value.



There are no longer any red lines because the highest peaks are well below the ceiling (they're at -3dB, as I specified). But the waveform is still clipped. You can clearly see the straight horizontal line between 0.0010 and 0.0020. The resulting file won't be as loud as the original but it will still be just as distorted.

If you want to see clipping in Audacity (the red lines), download your MP3 from your original topic and load it directly into Audacity. Make sure that "Show Clipping" is checked and you will see plenty of red.

One thing I noticed in the Audacity forums is that a few people claim that exporting to MP3 can increase the level slightly in places, causing clipping where there was none before. That's why they recommend setting the normalization maximum amplitude to -1.0 dB. That 1dB of headroom should prevent the conversion to MP3 from causing clipping. But, in my experience, -0.1 dB works just fine. I've exported to MP3, then brought the MP3 back into Audacity to check for clipping and found none. Or, if there was any clipping, it was so minor (just a few red lines) that nobody would be able to hear it. Whichever value you use, it might be a good idea to bring the MP3 back into Audacity after normalization to check for clipping. After you've done that a few times and you're satisfied that the value you used isn't causing any clipping, then you can confidently use that value in the future without having to check your MP3 anymore.

[phantasm777]

doesn't manually enveloping a track or song, reduce the clipping enough? or is normalizing better?

[Flash Harry]

Just a quick note -  If you record in 24 bit you can keep all of your recorded tracks well within the 0dB limit and mix to below 0dB. This ensures that you never clip. Then when you master to 16 bit, normalise as you master. You keep the signal to noise ratio of 16 bit recordings and the dynamic range of your recordings.
Having those extra 8 bits during the recording and post production process gives you the room to play with without loss in final quality.

[phantasm777]

seeing the clipping seems to have improved my recordings a bit, far as clearness and minimizing distortion. for some reason I never payed attention to the clipping option in audacity,. now it is a mainstay!

[T.C. Elliott]

Two quick notes: one is that I use -0.3 when I limit tracks (to increase volume without clipping) but only because I got used to the preset on the limiter plugin I was using. It seems to be a really good value, though.

I forget in Audacity, but on the master fader or main value if you play through your song and make sure that the value never hits 0.0 or higher... generally by playing the loudest parts which are usually the parts with the most tracks vs the loudest part that is more sparse... in other words, if your lead guitar section drops out the vox and you attenuate or automate the bass/drums down just a hair you'll actually have a louder single track but possibly a more quiet total sound level.

Using a very light hand and a limiter or compressor on the master fader can keep clipping to a minimum and if you have a good compressor it can make it sound a bit better, too. But in general, I try to make my mixes with lots of headroom ( a couple dbl) in case I ever get someone to master the track (yeah, I know, unlikely.)