Completed: Proposal Normalize

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Proposal pages help us get from feature requests into actual plans. This page is a proposal to rationalize and improve the Normalize effect.
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

Users familiar with "Normalize" in other audio software wrongly assume our Normalize will behave likewise and treat a stereo pair as a single "track". Normalize does not do this and provides no option to do so. Amplify does so, but is assumed to be the wrong tool (and by definition can only bring multiple tracks to the same level by running it multiple times).

Novice users get confused between Amplify and Normalize. They choose Amplify because the name sounds familiar and is top of the menu, but the typical novice may be recording unbalanced tapes or records from consumer hardware, in which case they would benefit from Normalize used in a proper workflow.

  • Users thus often choose the incorrect effect for their needs.
  • Users of Normalize can unwittingly damage their stereo balance.
  • There is support overhead in explaining the differences between the two effects and in ensuring users understand that Normalize operates independently on stereo channels.


The Solution - Audacity 1.3.14 and onwards

For 1.3.14 the Normalize effect has been enhanced to address issues in this proposal. In particular:

  1. minus sign moved to text box
  2. allow stereo normalizing, new checkbox added
  3. default to stereo normalizing
  4. positive values disallowed in the dB box
  5. text disallowed in the dB box
  6. default maximum amplitude set to -1.0 dB (a sensible value, and showing that it should be negative to new users)
  7. the dB box has been centred
  8. presets from previous Audacity versions ignored
  9. don't do an analysis pass if we don't remove offset, which gives comparable speed to Amplify if offset removal is not done
  10. The documentation (the Manual and the Wiki) has been updated to reflect these changes.



Proposed Feature

Normalize continues to set the level of all tracks independently, but a new checkbox offers a choice to normalize a stereo pair as a single track as well as the current behavior of normalizing each stereo channel independently.


Developer/QA Backing

  • Peter: I would like to see stereo pairs handled as a single track in Normalize prior to 2.0 if possible
  • Gale: I support this proposal while preferring the Proposal Normalize & Amplify Consolidation which makes one tool for Amplify and Normalize. Both proposals give Normalize a way to handle stereo pairs as a single track but I think merging has greater long term benefit. I think the checkbox to "Normalize stereo channels independently" in either proposal should initialise "checked" for backwards compatibility and differentiation with Amplify.
  • Steve
  • Bill: +1 for stereo pairs handled as a single track in Normalize before 2.0.
  • Martyn: I'm with Peter and Bill on this one. I don't even want a checkbox to do them independently, but concede that it is wanted.
  • Vaughan: I'm opposed to removing the ability to Normalize stereo channels independently.
  • Roger Dannenberg: Independent normalization of each track seems to be very odd and unexpected behavior.


Use Cases

  • Stereo balance/images can be damaged by inappropriate use of the Normalize effect.
  • A loud click in one channel can cause Normalize to create an unwanted change in the stereo balance.
  • Unbalanced stereo tracks due to an unbalanced recording chain need correction.
    • Steve: The correct tool for balancing stereo channels is the pan slider... independent channel Normalize could cause a left/right imbalance when the stereo track was correctly balanced before.
    • Gale: Pan is a hit and miss corrective requiring mix and render to see the waveform result. Pan will never scale up the stronger channel. A typical USB record or cassette player recording will be unbalanced, and cassette recordings won't have clicks to destroy the rebalancing. See the Talk Page.
  • Normalizing in Chains without altering the stereo balance - see this thread from the forum.


Details

  • Add checkbox "Normalize stereo channels independently"
    • When checked, Normalize behaves exactly as now.
    • When unchecked, Normalize sets the level of a stereo track based on whichever channel contains the peak and then scales the other channel by the same amount - like "Amplify" does on a single stereo track. Otherwise, tracks are still normalized independently to the required level.
    • Previous setting made by the user to be "remembered" for next use.
    • Consensus is that default should be "unchecked", but if it is felt that this is too big a change from current behavior then default could be "checked"
      • Bill, Steve, Peter, Martyn & Roger: +5 for default to OFF
      • Gale: +1 for default to ON (to maintain current default behavior to prevent nasty surprises)


GUI Example

Normalize stereo mods.png


Related Proposals

There is a proposal on the Wiki to rationalize Audacity's handling of DC offset removal which is related to this proposal, but does not compete with it.


Previous Feature Requests relating to this proposal

See the Talk page


Footnote

To quote from the Wiki Page Amplify and Normalize: "These are very similar effects, but have some subtle differences. Normalize has its own option for correcting DC offset. Amplify has its own options to enter the required volume change directly, and to allow "clipping" by amplifying to above 0.0 dB. The two effects behave differently if used on multiple tracks or channels." and "Audacity's Normalize effect breaks with the convention of many other audio applications. In those applications, "normalize" maximizes multiple tracks against the peak level common to all of them, so retaining their relative balance."

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