Clipped wav files upon opening.

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ChuckBarnett
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Clipped wav files upon opening.

Post by ChuckBarnett » Thu Mar 15, 2018 3:05 pm

fullwindow000.png
fullwindow000.png (81.87 KiB) Viewed 184 times
I'm not but an occasional user of Audacity and this must surely be an entry-level issue.

Most of my use of Audacity is to convert files from wav to mp3. I use Amazing Slow Downer to change key and perhaps speed and then open that wav file with Audacity. This screenshot is typical and I don't think the peaks should be full frame?? Is this what clipping looks like? How do I eliminate that?

Thank you! And thanks again for this program!

Chuck B

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Re: Clipped wav files upon opening.

Post by steve » Thu Mar 15, 2018 3:55 pm

ChuckBarnett wrote:I don't think the peaks should be full frame?
No, normally there should be mostly space around the waveform with just a few peaks getting close to the top/bottom.
The "loudness war" has tended to push more of the waveform close to 0 dB, but I'd guess that from about 50 seconds onward, that track sounds noticeably distorted. Am I right?

Unfortunately, anything more than occasional clipped peaks is likely to be permanent and irreparable. The "trick" is to be careful with levels to avoid it happening.

Audacity has an unusual trick up its sleeve - if you "overcook" a track during processing in Audacity, and assuming that the track sample format is 32-bit float (default), then clipping need not be fatal. 32-bit float format can support signal levels well over 0 dB, so if a track goes over 0 dB as a result of processing in Audacity, then the track can be rescues by "amplifying" it by a negative amount so as to bring it back into range (below 0 dB). Unfortunately this will not work for tracks that are damaged before being imported.
ChuckBarnett wrote: I use Amazing Slow Downer to change key and perhaps speed
You're aware that Audacity has effects for changing pitch and speed? (see: https://manual.audacityteam.org/man/ind ... er_pitched)
9/10 questions are answered in the FREQUENTLY ASKED QUESTIONS (FAQ)

kozikowski
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Re: Clipped wav files upon opening.

Post by kozikowski » Thu Mar 15, 2018 5:39 pm

View > Show Clipping. You may have an occasional thin red line maybe every minute or so. Maybe not.

As above, if you created this damage inside Audacity, you can easily recover with any of the volume tools such as Effect > Amplify.

If the damage happened outside Audacity, that's the end of the world.

Koz

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Re: Clipped wav files upon opening.

Post by kozikowski » Thu Mar 15, 2018 5:43 pm

One more note. It's not unusual for capture or production to have different specifications than delivery or final. For example, live recording for audiobooks recommendation is quieter than the delivery work. Much of that comes from live recording being harder to control than the files going out the door to the client.

Koz

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Re: Clipped wav files upon opening.

Post by DVDdoug » Thu Mar 15, 2018 5:46 pm

Does it sound Ok?
Is this what clipping looks like?
Yes. It's either clipped or severally limited.* You'd have to zoom-in to look at the peaks and you might have to reduce the level (the Amplify effect with a negative dB value) so you can see if the top of the wave if it goes over 0dB (1.0).
How do I eliminate that?
There is a Clip Fix effect but its impossible to know the height & shape of the original waveform. So it's best if you can prevent it.

If you turn on Show Clipping you should see red. But, the algorithm doesn't analyze the wave shape, so red means potential clipping.

You'll see red if the waveform goes over 0dB without clipping (although it will be clipped if you export to regular WAV).

Or if you have a clipped waveform and you reduce the level, it will still be clipped (the wave shape won't change) but Audacity won't show red.
I use Amazing Slow Downer to change key and perhaps speed and then open that wav file with Audacity.
Did you "look at" the waveform before running it through Amazing Slow Downer? That's probably not the cause, but it's worth checking.
Most of my use of Audacity is to convert files from wav to mp3.
As you probably know, MP3 is lossy. The wave shape changes and some peaks get higher and some get lower. So it's not unusual for some new-peaks to go over 0dB (+1dB or so). It's not (necessarily) clipped because MP3 can go over 0dB without clipping, but Audacity will show red (probably abut half of the MP3s I've ripped from CD show red) and if you play it at "full digital volume", your digital-to-analog converter will clip. I've never heard of a case where this clipping was audible, but some people like to normalize to about -1dB before making an MP3.



* Excessive limiting and look like (and sound like) clipping. In fact, the Audacity Limiter effect has options for intentional clipping.

ChuckBarnett
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Re: Clipped wav files upon opening.

Post by ChuckBarnett » Thu Mar 15, 2018 5:56 pm

THANK YOU for that important bit of information! I'll check that out.

I opened that same original mp3 file in Audacity and see the same result -maxed out peaking throughout the song. Is there some setting I need to consider? a check box or something?

ChuckBarnett
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Re: Clipped wav files upon opening.

Post by ChuckBarnett » Thu Mar 15, 2018 6:20 pm

Screenshot (10).png
Screenshot (10).png (106.61 KiB) Viewed 170 times
I found the setting to see clipping (this is on the original mp3). How do you buy music that has clipping???

ChuckBarnett
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Re: Clipped wav files upon opening.

Post by ChuckBarnett » Thu Mar 15, 2018 6:23 pm

Playing the song through Audacity on my laptop -hard to tell if it sounds bad because nothing much sounds good...

kozikowski
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Re: Clipped wav files upon opening.

Post by kozikowski » Thu Mar 15, 2018 6:39 pm

Right. This is when you plug in your headphones. Doing quality judgements in the field isn't recommended, but trying to listen on laptop speakers is useless.

I have a set of earbuds I really like with tiny custom muffs that fit my ears well. They're not as good as real headphones, but they're way better than laptop speakers and they fit in my travel pack.

Koz

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