"Show Clipping" Options

[Edgar]

How many votes are required to repair a broken tool?

Probably the wrong question. If something is broken then fixing it is not a matter of opinion, it needs to be fixed.
The questions are:
* How much priority should be given to fixing it.
* How many votes are needed to convince a developer that a feature is broken.

I'm not convinced that it is broken

I have not looked at the code but I suspect that in each of the three instances there is a variable which is used as the definition for "number of clips samples before clipping is defined". I suspect it would be trivial to make them all match. What would need discussion is "what do we match". Currently, in the analyzer affect Find Clipping we default to 3; making the other two match this default should be trivial. Find Clipping does not store its "last used" values in the configuration file so, without making it do so, we may not use this as a method of setting a user defined default.

This should be a very easy fix if you QA folks can decide on a specification I will write a patch.

[steve]

if you QA folks can decide on a specification

My vote is that a red warning line should be shown whenever a sample touches or exceeds 0 dB.
0 dB is an absolute limit for integer format audio and I disagree with putting off the warning until there is obvious damage. Warnings are intended to "warn", and sample values at 0 dB is an appropriate level to warn about clipping. What's the point of warning someone about a cliff edge after they have fallen from it?

There already is "a volume control on the fire alarm" (nice analogy koz )
If the waveform just touches 0 dB here and there, you will see a few thin red lines.
If the waveform blasts into 0 dB regularly, there are thick red bands.

[Gale Andrews]

I was not happy with the description in the manual, so I have updated it:

Click this menu item to turn display of clipped samples on and off - a check mark in the item indicates that display is turned on. A clipped sample is one that is outside the volume envelope defined by +1.0 to - 1.0 (this is the vertical scale to left of the waveform when default Waveform view is enabled, as shown below). Clipped samples are bad, as they cause distortion and lost audio information - avoid them where possible, for example by setting the recording level correctly. Red vertical lines are displayed as a warning whenever a sample value touches or exceeds 0 dB. A solid block of red will usually indicate severe clipping. Turn "Show Clipping" off if it behaves sluggishly on slower machines.

I wasn't happy either but we were in freeze when I noticed it.

I think the above still implies that a red-marked clipped sample is outside the volume envelope, but the marking is for "touching or outside" as I understand it.

So I had a go and also stated what the trigger level is in Show Clipping and Meter Toolbar. I think it's worth saying, even if y'all decide to change the trigger level.

So it says now:

Click this menu item to turn display of clipped samples on and off - a check mark in the item indicates that display is turned on. If turned on, individual or multiple clipped samples display as a red vertical line when in one of the waveform views. A sample is displayed as clipped if it touches or exceeds 0 dB and so touches or exceeds the volume envelope defined by +1.0 to - 1.0 on the vertical scale to left of the waveform.

A run of four or more consecutive clipped samples will also trigger the red clipping indicator in Meter Toolbar. A solid block of red in the waveform will almost certainly indicate multiple or extended runs of lost audio information above 0 dB, resulting in severe distortion. Avoid clipped samples where possible, for example by setting the recording level correctly. You may turn "Show Clipping" off if it behaves sluggishly on slower machines.

Over to you if you want to tweak my tweaks.


Gale

[Gale Andrews]

if you QA folks can decide on a specification

My vote is that a red warning line should be shown whenever a sample touches or exceeds 0 dB.
0 dB is an absolute limit for integer format audio and I disagree with putting off the warning until there is obvious damage. Warnings are intended to "warn", and sample values at 0 dB is an appropriate level to warn about clipping. What's the point of warning someone about a cliff edge after they have fallen from it?

They may not have fallen off it if they are only touching 0 dB or only over it one sample at a time. They will probably only fall off it in that case if they export MP3 or have less than perfect playback equipment.

I can't see we could entertain separate options for Show Clipping and Meter Toolbar. Is there any support for a user-specified trigger that acts the same on all three of Show/Find Clipping and Meter Toolbar? Where would that option go? Would it be acceptable to put it in Meter Preferences only? If so and a default of three clipped samples is reasonable, it means that Show Clipping by default is then less inclined to show clipping.

On the whole I only vote for one change - move the Meter Toolbar trigger threshold to three or more samples. Let those zooming in on the waveform still be able to see a marking for an individual clipped sample, if they turn Show Clipping on.


Gale

[steve]

They may not have fallen off it if they are only touching 0 dB or only over it one sample at a time.

Precisely my point - they may still be standing on the edge of the precipice - isn't that a good time to warn them?

In an ideal world, audio tracks in Audacity would always be 32 bit float format, then we could measure the severity by "how far over 0 dB", but that can't work while tracks may be integer format because integer format is never over 0 dB.

[kozikowski]

My vote is that a red warning line should be shown whenever a sample touches or exceeds 0 dB.

I don't agree and neither does the person whose thread this is. It's not "I might possibly create sound damage any second now if I'm not careful." The red bars indicate the presence of Clipping Damage. It's not unusual for heavily compressed work to display one-sample red flags and have little or no actual sound damage. I think three (or four) successive samples at 0 (either direction) is a good indicator. Also, you don't need advanced warning in post production.

I do agree that the sound meters might warn ahead of time, that's consistent with good live recording practices, but that opens up the problem of warning conditions. Do you warn 3dB ahead?? That's not a clip indicator.

I'm also in the camp of people who want the sound meter peak flashers to automatically fade. In my world, they're only useful once per take. In the unlikely event they come on, I'm not going to start poking at the meters trying to remember where the reset is during an expensive sound shoot. Not happening.

Koz

[steve]

I'm also in the camp of people who want the sound meter peak flashers to automatically fade. In my world, they're only useful once per take. In the unlikely event they come on, I'm not going to start poking at the meters trying to remember where the reset is during an expensive sound shoot. Not happening.

You will be able to see precisely where the peak meter flashed by looking at the red warning lines on the waveform - assuming of course that the red warning lines are there.
I'm of the the camp that would rather look for myself to assess the damage rather than relying on the computer to decide that the damage is insignificant.

The argument could be described as; whether to raise the alarm at the first whiff of smoke, or wait until you see the flames. I prefer the former, because then I can check if there is a fire, and if not, then I can safely ignore the alarm. Audacity even provides a tool to help asses the damage: http://manual.audacityteam.org/o/man/find_clipping.html

[Gale Andrews]

I'm also in the camp of people who want the sound meter peak flashers to automatically fade. In my world, they're only useful once per take. In the unlikely event they come on, I'm not going to start poking at the meters trying to remember where the reset is during an expensive sound shoot. Not happening.

You will be able to see precisely where the peak meter flashed by looking at the red warning lines on the waveform - assuming of course that the red warning lines are there.

Not necessarily true, Steve. Show Clipping shows individual clipped samples that touch or exceed 0 dB but the meter requires four such consecutive samples. So you can't judge where clipping in the meters started by looking at Show Clipping. You can judge it by using Find Clipping and changing the start threshold to 4 samples.

I'm fine if Show Clipping had an option to only display runs of more than a chosen number of samples. But I strongly think it should always be able to show individual samples at 0 dB or above.

I don't think it ideal that the trigger number of samples is different for all three clipping display methods. But it has to be so if we don't want a way to change the threshold for all the methods. I don't think Meter Toolbar should default to showing clipping as soon as it finds a single sample touching or exceeding.

@Koz - to reset the clipping indicator in either meter in 2.0.6 or earlier, click anywhere in or on the Recording Meter.

In 2.0.7, click in or on either meter to remove a clipping indicator in one of the meters. If both meters show clipping, click in or on both meters.

Gale

[steve]

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.

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?

I'm fine if Show Clipping had an option to only display runs of more than a chosen number of samples. But I strongly think it should always be able to show individual samples at 0 dB or above.

Same here, though I think that 'increasing the number of samples before showing red lines' encourages new users to record too hot, and for MP3 files it will tend to not show clipping when clipping is clearly present (making it a "dangerous" option).

[steve]

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.

testsample.mp3

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