"Show Clipping" Options

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steve
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Re: "Show Clipping" Options

Post by steve » Thu Oct 30, 2014 6:37 pm

A "better" (more reliable) way to detect clipping, would be to
look for a run of "N" samples that are above a "threshold",
where the "threshold" is ("peak level" - "tolerance"),
and "tolerance" is specified in dB.

For simple digital clipping, "tolerance" could be set to zero. For analogue clipping, or if the audio has been converted to a lossy format, "tolerance" would need to be greater than zero (usually a fraction of 1 dB).

This is not perfect
  • it requires some knowledge for setting up,
  • it cannot run in real time,
  • it can be fooled if the recording level was not constant,
  • it will only provide reasonable results when set up appropriately for the type of material,
  • it requires some knowledge to correctly interpret the results,
but it would be more accurate when used correctly.
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Gale Andrews
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Re: "Show Clipping" Options

Post by Gale Andrews » Fri Oct 31, 2014 1:12 pm

steve wrote:
Gale Andrews wrote:Not necessarily true, Steve. Show Clipping shows individual clipped samples that touch or exceed 0 dB but the meter requires four such consecutive samples.
Of course you can find where the clip meter came on during a recording :?
I doubt that koz sets his recording level anywhere near 0 dB. If the clip indicator on the meter came on, then it will show on the track when "Show Clipping" is enabled. There will be a red line at the first sample to reach 0 dB, and a red line for each additional sample that is at or above 0 dB.
Yes, but there may have been individual clipped samples before the run of four or more that triggered the meter clipping indicator.

If you are actually zoomed in far enough to distinguish a single red sample line from a run of four red sample lines, then of course I agree you can find where the first run of four lines is. Most people will not be zoomed in far enough (and if they are, there will be much tedious scrolling required to find the first run of four if there are also individual clipped samples).
steve wrote:If we only have red lines when there are "N" or more samples at or above 0 dB (let's say "4" for sake of argument), then where exactly will the red line(s) go? Will every sample >= 0 dB still have a line?
Good question - but again it is only a question when zoomed deep in. Perhaps the first N samples would be displayed as a group with a small number corresponding to "N", then consecutive samples after the first "N" would be displayed individually?
steve wrote:This file illustrates why we should show "clip lines" for single samples at or above 0 dB.
If we only show red lines when there is a sequence, this would look OK (based on the absence of the warning), but listen to it.
Or rather, look at it. If you had posted only the first 1.5 seconds of it, even single sample Show Clipping finds no problem. As you say in your follow-up post, clipping should also be looked for below full scale. That track you posted could also have been normalised to -6 dB and would still sound almost as bad, or there could be soft clipping below full scale due to hardware features or bugs.
steve wrote:I think that 'increasing the number of samples before showing red lines' encourages new users to record too hot
Leaving aside what an amplitude threshold of clipping might be, if they don't get the clipping indicators in Meter Toolbar when recording, then almost certainly they won't hear clipping (in an exported WAV and on good equipment). Also only more advanced users will turn "Show Clipping" on (and understand what it is trying to do).

But seeing red lines in the waveform but no clip indicator in Meter Toolbar is confusing IMHO. I would have no problem if the default trigger for Show Clipping was three or four consecutive clipped samples (whatever Meter Toolbar was) as long as there was a way to show individual clipped samples too.


Gale
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steve
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Re: "Show Clipping" Options

Post by steve » Fri Oct 31, 2014 3:17 pm

Gale Andrews wrote:But seeing red lines in the waveform but no clip indicator in Meter Toolbar is confusing IMHO.
Theoretically yes, but in practice it is virtually impossible to make a recording that "just touches" 0 dB (that is, only single samples touching 0 dB). If the recording is that hot that occasional samples touch 0 dB, then it is very close to a certainty that there will be "actual" clipping somewhere in the recording.

Even "theoretically", if one sample "touches" 0 dB, then unless that sample is at the very top of a peak, then it is, arguably a "clipped" waveform (not that it is likely to be audibly clipped, but if we want to argue about the minute detail):
clipped.png
clipped.png (17.19 KiB) Viewed 855 times
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kozikowski
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Re: "Show Clipping" Options

Post by kozikowski » Mon Nov 03, 2014 4:14 am

I haven't read the thread yet. Life has a way of encroaching.

User interface attached.

Koz
Attachments
clippingControlPanel.jpg
clippingControlPanel.jpg (60.39 KiB) Viewed 847 times

Gale Andrews
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Re: "Show Clipping" Options

Post by Gale Andrews » Mon Nov 03, 2014 1:03 pm

kozikowski wrote:User interface attached.
Is the "Clip Threshold" meant to apply to both View > Show Clipping and Analyze > Find Clipping?

Where are you proposing to place those preferences?


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steve
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Re: "Show Clipping" Options

Post by steve » Mon Nov 03, 2014 4:17 pm

kozikowski wrote: CLIP THRESHOLD OPTIONS
Default (3 samples over) [X]
For integer format tracks (16 / 24 bit), you can never go over 0 dB. So if we take that option setting literally (how else?) then setting then the current default threshold of 0 dB will never show clipping for 16 bit or 24 bit audio.
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kozikowski
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Re: "Show Clipping" Options

Post by kozikowski » Mon Nov 03, 2014 6:18 pm

Again, I haven't plowed through the whole thread. Any time interval that stays zero for three successive will trigger an overload. The current tool seems to trigger at zero, doesn't it? Use that value x3.

The overload illustration is of sound that is very close to or right on the Nyquist restriction rate. As a result, the distortion is going to be far higher than audible, even if you are a little girl. That plays to the philosophy of making the show sound OK even if it's not scientifically accurate.

I'm reducing the number of tools from three to two. The setup panel posted will allow you to search for overload points wherever you want them to include having the flasher and red bars match as an option. I think being able to search positive and negative overload points independently is a solution searching for a problem. I think if it quietly vanished from 2.0.7, few regular users will miss it.

Koz

steve
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Re: "Show Clipping" Options

Post by steve » Mon Nov 03, 2014 6:39 pm

I can see the sense in having the same algorithm form both the waveform red vertical lines and the meter clip indicators, but if that is the case then I think that it needs to be easily configurable (as per koz's suggestion).

If the two are linked, then an obvious and convenient place for the options would be in the meter preferences (meter dropdown > Preferences).

Note that I didn't say that I thought that both "View > Clipping" and the meter clip indicator should have the same settings - just that they should use the same algorithm. My preference would be to show clipping on one sample hitting the threshold, but I think that 4 samples for the meters and 1 sample for "View > Clipping" are reasonable defaults.
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Gale Andrews
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Re: "Show Clipping" Options

Post by Gale Andrews » Tue Nov 04, 2014 1:01 pm

steve wrote:I can see the sense in having the same algorithm form both the waveform red vertical lines and the meter clip indicators, but if that is the case then I think that it needs to be easily configurable (as per koz's suggestion).

If the two are linked, then an obvious and convenient place for the options would be in the meter preferences (meter dropdown > Preferences).
I suggested that somewhere here too, but that's another case (like Meter/Waveform dB range) where we would be conflating settings that some might want separately findable as well as separately configurable. I don't think we want to go that road. For example I might want to hide the meters to save space and rely on Show Clipping.

I suppose since Find Clipping is already configurable, it can remain independent of any separate or combined "clipped samples" threshold for meters and Show Clipping. Find Clipping can't be removed - VI users can't see the meters and clip lines.
steve wrote:Note that I didn't say that I thought that both "View > Clipping" and the meter clip indicator should have the same settings - just that they should use the same algorithm.
We only have one algorithm so far, don't we?
steve wrote:My preference would be to show clipping on one sample hitting the threshold, but I think that 4 samples for the meters and 1 sample for "View > Clipping" are reasonable defaults.
I know that allowing no configuration of number of samples is a pseudo-reason for having meters and Show Clipping work on different number of samples. However I think that is so unintuitive that it should change so that the default number of samples is the same for both.


Gale
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steve
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Re: "Show Clipping" Options

Post by steve » Tue Nov 04, 2014 1:55 pm

Gale Andrews wrote:I don't think we want to go that road.
Which road would you prefer to go down?
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