Difference between revisions of "Proposal Easy Avoid Clipping on many tracks"

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(QA Backing: My take on this)
(Developer Backing: '''Roger wrote by email 25Aug20:''' The master fader has a lot of support.)
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==Developer Backing==
 
==Developer Backing==
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'''Roger wrote by email 25Aug20:''' The master fader has a lot of support.
  
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One thing I can imagine is *after* you save, if there was clipping, a dialog tells you:
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{{note|
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'''Your signal clipped with a peak of 1.7. What would you like to do?'''
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*Reduce the master fader automatically and save again.
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*Reduce the master fader but do not save yet.
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*Nothing. }}
  
 
==QA Backing==
 
==QA Backing==

Revision as of 09:03, 26 August 2020

Proposal pages help us get from feature requests into actual plans. This page is a proposal to save users the tedium of changing the levels individually on multiple tracks when their track balance is already satisfactory but shows clipping.
Proposal pages are used on an ongoing basis by the Audacity development team and are open to edits from visitors to the wiki. They are a good way to get community feedback on a proposal.


  • Note: Proposals for Google Summer of Code projects are significantly different in structure, are submitted via Google's web app and may or may not have a corresponding proposal page.

The Problem

It is far to easy for a user to export an audio file from a multi-track project that is clipped - even though each individual track is well below clipping threshold. We offer no warning in the app to the user about this when it is occurring.

Multiple tracks will probably be collapsed. Therefore the gain sliders may be especially hard to access with a mouse. Probably the track info should be the first content to disappear when dragging the track up, not the last.

Tracking

Bug 565: Easier way to avoid clipping on multiple tracks. Update the Bugzilla issue with the consensus solution achieved here.


Proposed Solution

There are several ideas, not necessarily mutually exclusive, but of increasing complexity and functionality:

  • Shortcut and/or "always visible" master fader slider that moves all gain sliders by the same amount.
    • Incorporate the master fader slider into the playback meter (and the recording input slider into the recording meter).
  • Interface to select multiple tracks on which selected tracks the mute/gain/pan solo controls operate in tandem. Could be integrated into Mixer Board.
  • Automatic gain adjustment (Mix and Scale) so that the mix in unmuted tracks can never clip. Could be a control that sets the target level of the mix.
  • Separate mixing window (like Mixer Board but with a "Master-Fader" control).
  • Master-Fader or Master Envelope track, used additional to and independently of Envelope Tool.
  • Fader Automation. Adjust the Mixer Board or Track Control Panel gain sliders while playing then record the slider moves so you can render them if desired.


Pros and Cons

Pro

Cons

Developer Backing

Roger wrote by email 25Aug20: The master fader has a lot of support.

One thing I can imagine is *after* you save, if there was clipping, a dialog tells you:

Your signal clipped with a peak of 1.7. What would you like to do?

  • Reduce the master fader automatically and save again.
  • Reduce the master fader but do not save yet.
  • Nothing.

QA Backing

  • Gale: who prefers "automatic mix and scale", or a slider/shortcut to move all gain sliders in tandem. I understand these are easier to implement than envelope solutions (at least to begin with).
  • Peter: At the very least we should offer a warning if the output file is likely to clip and ask if the user wants to proceed - better would be automatic clipping avoidance either as part of the export (and advised to the user) or as a tool available to apply to projects or selected tracks within a project.
  • Bill 25Aug2020: I like Steve's comment #3 in bugzilla - a clipped mix is user error. If we want to automate this then we need to first do the mix looking for the peak, then do the mix again adjusting the overall gain but only if there was clipping. Or do we want to automatically normalize the mix as well? Proposals such as a master fader track with automation similar to a time track will not prevent the user from shooting themselves in the foot. If we implement this my first thought is it should be a checkbox in the Export dialog "Normalize mix" or "Prevent clipping".
    Telling the user to Mix and Render then Normalize only works if they are in 32-bit float; if they are in 16-bit the returned mixed track will already be clipped. The advantage of doing it ourselves in one go is that we always mix in 32-bit float regardless of project settings.

Details of possible solutions

Automatic Mix and Scale

This means that the tracks never clip. If you add a track, or change a gain on one track, then on mix or playback the gain sliders adjust to respect the proportional volume of each track, without clipping. Probably best as a Preference to choose scaling or not.

Keyboard shortcut to move gain sliders in tandem

When the shortcut is held down, moving the gain slider on one track moves the gain sliders on all the other tracks by the same amount. User decides if the final level clips or not.

Master Fader Slider

See https://forum.audacityteam.org/viewtopic.php?p=185748#p185748 for idea by Steve/Bill for a Master Fader slider which would be accessible in two places

  • in a Master Fader Track (with envelope points written when moving the fader)
  • in Mixer Board.

Mixer Lister

Suggested by Alex Taddei. See https://wiki.audacityteam.org/pdf/mixer_lister.pdf.

Mister lister proposed interface

This idea creates a tabular interface for all the tracks, not unlike Mixer Board, with gain/pan/mute/solo controls and a right-click context menu for Sample Format and Sample Rate.

  • Each track has a checkbox to select that track, and a "Select All" button.
  • Changing any control, rate or format in a selected track makes the same changes in all the selected tracks in the interface.
  • Tracks can be dragged up and down as in Track Control Panel (Mixer Board does not support this).
  • Changes are not applied to the Track Control Panels until pressing "OK" in the interface.
  • Selecting tracks in the interface does not select tracks for editing in Track Control Panel.

Gale 17Feb13: I give it a cautious welcome if integrated into Mixer Board as a way of changing controls on multiple selected tracks at the same time. I don't think we need "OK". If you lock tracks together by the checkbox, then the controls for those tracks move in sympathy and affect the Track Control Panels simultaneously.

I am not sure how often you would want to change the sample rate or format of all (or individual) tracks - this may be unwanted. I'm not sure how often you would want to gain or pan large numbers of chosen multiple tracks by the same amount (as opposed to gaining or panning all tracks by the same amount). For gaining all tracks I still prefer a clean "Mix and Scale" Preference or a shortcut slider to move gain sliders in tandem.


Other Background

Indicative Feature Requests July 2012 - vote counts updated 25Aug20

  • One-step way to avoid clipping on multiple tracks: (30 votes)
    • Master Fader ability: (27 votes)
      • Automatic gain adjustment (Mix and Scale): (14 votes) so that the mix in unmuted tracks can never clip. Could be a control that sets the target level of the mix.
      • Shortcut that moves all gain sliders by same amount (8 votes)
      • Separate mixing window (like Mixer Board but with a "Master-Fader" control): (7 votes)
      • Master-Fader or Master Envelope track: (3 votes) Like the Envelope Tool but in its own track and applies to all tracks, used additional to and independently of Envelope Tool. On playback, fader position is interpolated (linearly in dB) between the track points and the result is added (in dB thus multiplied) with the current "envelope" value.
  • Fader Automation:
    • Adjust the Mixer Board or Track Control Panel gain sliders while playing then record the slider moves so you can render them if desired. (4 votes). Common feature on many other multi-track audio programs. In this way one can build up a mix, adjusting individual tracks and tweaking levels until just right. This would first require changing to linear envelope points. Could be extended to panning (if we had a pan envelope).
      • Panning Envelope has (42 votes) on Wiki Feature Requests.