User talk:PeterSampson/Proposal: Improvement and rationalization of Normalize

Nomenclature for "Link Stereo Channels"
Peter: I have started this section to enable us to discuss, and to come to a consensus, on the actual text for what we are now referring to as "Link Stereo Channels". Gale does not like this current suggestion, Ed has suggested a couple of alternatives in a recent email thread (transferred here)"Link Stereo Channels":
 * Ed:Maybe instead of "Link stereo channels" could be "Normalize stereo channels linked" or "Normalize stereo channels as one track"; maybe even a "details" button linking to the manual page covering the implications of linking stereo before normalizing.
 * Gale: If we accept it's more usual for Normalize to treat a stereo track as a unit, make the *option* (the "unusual" action) to "Treat stereo channels independently" or similar as I've suggested on the v4 Proposal. Ed's idea is OK (if long) - Another could be "Retain balance between stereo channels".
 * Peter: <<"Treat stereo channels independently">>  This, or similar, is a great step in the right direction Gale. We've all been thinking of "linking" just because they are not linked currently. Viewing it from the other way around with the channels normally treated as a unified-pair was smart thinking. And it lets us get away from that "link" word that you dislike so much in this context (and I do understand your reasoning here, given our other use of "Link" elsewhere in Audacity).
 * Ed:I also like this reversal of nomenclature. Maybe "Normalize stereo channels independently" which makes it clear the CB only affects the Normalize part of the combo (if we do a combo).
 * Peter: +1 I like Ed's wording, it makes it pretty clear what's going on (and thanks for the mock-up Ed).
 * Steve: +1 for the wording: "Normalize stereo channels independently".

Discussion re stereo channel linking - moved from the proposal page

 * Gale: <> Exactly, that is the "new feature" that I meant - scaling up (which we now call "Amplify") multiple stereo tracks independently one after the other, so they all end up at the prescribed peak in one channel or the other without change of stereo balance. We can do this with the new checkbox in Normalize, is that the intention?


 * Steve: It's only a small subset of user cases where there is any advantage for normalizing channels independently. The right tool for adjusting stereo balance is the pan slider. It should not be an unpredictable side effect of Normalizing. Complaints about stereo channels being Normalized independently are not very common, but people using "Normalize" without realising that it can adjust the stereo balance is alarmingly common. The usual assumption is that "Normalize" in Audacity will work in the same way as it does in the rest of the Universe. Gasps of disbelief are the reaction when they learn the shocking truth. Using the Amplify effect to Normalize is a "workaround" that we all repeat every week on the forum. As there is a "Normalize" effect, there really should be no need for a workaround. You can't Normalize multiple tracks at the same time with the Amplify effect, so the only workaround there is to use the Amplify effect on each track separately.
 * Gale: <>. But it's a hit and miss corrective - it's not that easy to guess what slider correction is needed (certainly not with default waveform view). Then you need to mix and render if you want to see the result. And pan will never scale up the stronger channel, but many users will want to "maximise" in one sense or another so then they still have to use Amplify after pan. So Normalize is I think the better general purpose tool. People with a click that is going to wreck the stereo balance should get rid of the click.

Previous Feature Request relating to this proposal
This Feature Request is taken from the Feature Requests page in the Wiki:
 * Option to calculate track gains together to avoid changing stereo balance: When multiple tracks are selected, only the highest peak level of ALL tracks should be considered to adjust each track by the same amount so that the volume of each track relative to each other will stay the same. (9 votes)
 * Gale: This is what Effect > Amplify does. Some people would argue "Amplify" should be called "Normalize", or we should have an option inside "Normalize" to "Normalize stereo channels independently". If unchecked, this would retain the channel balance in stereo tracks (while still letting all tracks be normalized independently). Then some people envisage Amplify and Normalize could be merged into one effect, but care is needed so that too many options are not provided which could make a single effect too complex.

Notes from the forum

 * Ral-clan: Yes, I agree that if Audacity doesn't link the two channels when it Normalizes, then that function is fairly useless.
 * Koz: quoting Ral-clan "I think it might be useful if there was a tick box in the Normalize function that offered something like "tie stereo pairs" or "preserve stereo balance" as an option. That way one could import a number of stereo songs and normalize them all to the same level, but keep the relationship between each song's left and right track intact."
 * That's how I thought it already worked. Imagine my surprise. I believe it should normalize a stereo pair tied and independently if they're split. Normalize should introduce no damage and only change levels. Changing the stereo image is show damage, and better, it's damage that you can't readily recover from without UNDO.
 * Ral-clan: I agree that the way Normalization works independently on each track of a stereo pair in Audacity seems counter intuitive to me, as someone who mixes down and prepares home music studio recordings for burning to CD. I also agree that, intuitively (it seems to me), Audacity should by DEFAULT lock the balance of stereo pairs when normalizing and only adjust MONO tracks independently (another option would be to add a toggle checkbox to Normalization to set balance locking / unlocking of stereo pairs). I'm surprised more people don't feel the same way as this type of normalization is something a lot of people do after mix-down of music. Do they even know that Audacity's normalize function is destroying the stereo balance they've carefully mixed? If they did, would they be content with that?
 * Koz: I do almost everything with an idea of my audio peaks hovering around -3. It's a good compromise and is the only value available in Audacity 1.2. Audacity 1.3 gives you the ability to choose any value you want. I still pick -3.

Feedback from Bill Wharrie
Bill 11May11: Amplify and Normalize do two different things and I believe are appropriately named.
 * Amplify applies a fixed amplification factor to the selection. It calculates the maximum factor that can be applied to the selection and offers that as a default. If you select multiple tracks the effect still finds the peak value in the selection (i.e. across all tracks). "I want to amplify all my tracks by 3 dB."
 * Normalize makes the maximum peak level in each track in the selection the same. This is useful. In preparation for a multi-track mix you could normalize all tracks to, say, -6 dB or -9 dB. "I want to adjust all my tracks so the maximum peak amplitude in each track is -6 dB."
 * Gale: To clarify, Normalize still works on selections, ignoring regions outside the selection. So if we were to rename these two effects (which I think is an option for Normalize if developers don't want to allow it to "link" tracks or channels), distinguishing the effects by whether they work on tracks or selections would be too simplistic.
 * Bill: I'm not suggesting we rename the effects. And, yes, Normalize works on selections, but still works on each track independently. So what I'm suggesting is "Link Stereo Channels". This is the place where Normalize really breaks with every other effect and editing operation in Audacity.
 * Peter: Indeed all other effects in Audacity always work on a stereo pair as a single entity - a "track". In order to operate on each channel separately the user must "split" the stereo track.
 * For those who simply wish to normalize a stereo track (or even normalize multiple stereo tracks) I'd support a "link stereo channels" checkbox.

Feedback from Ed Musgrove

 * In general, I only use Normalize to repair DC offset (and only in others’ recordings as my system does not induce it).
 * Add a switch to Normalize to operate on a stereo pair as a single track - default set to "on" but let this be a Prefs setting

Feedback from Gale Andrews

 * I agree Normalize is more of a problem than Amplify, but I'm aware that novices may not see Normalize a long way down the menu, and even if they do, they are likely to ignore Normalize if they don't understand the word. So we still have an issue that Amplify won't help novices re-balance the tracks which is what a high proportion of them probably do need.
 * We still have an issue that people can't figure which tool to use which is why we wrote Amplify and Normalize.
 * Peter 13May11:: Yes, I recall from past postings on the forum that some of them even think that they have to use both tools. I do remember from when I had my ION iTT-USB that the manual recommended using Normalize as the final production step.  And that's also what Carla Schroder writes in her new "The Book Of Audacity" on p235 on Normalization.
 * Normalize kind of loses its point to me as a separate tool if it loses DC Offset (which I think it should) and then (by default) does the same as Amplify in operating on the hottest track. The only real difference then is the presentation of a target in Normalize and scale amount in Amplify. So I think there could still be mileage in having one volume adjust tool and its name should at least start with "Amplify". Some of its perceived complexity and decisions on what units it displays/whether target or scale is preselected/remembered could be removed to a preference.
 * Peter 13May11:: I know what you mean - but I have just been discussing this with an Audacity newbie (my wife) and for her I explained the differentiation as Normalize changes amplitude to a prescribed level whereas Amplify adjusts the tracks by a scaled - and that seemed to make sense to her. I fundamentally agree that if we were starting from scratch that a single amplitude adjustment tool would be the sensible way to design the UI.  But we have what we have and I do suspect that removal of one of the effects, or a merger, would look like a regression.
 * Gale: There was very little resistance from Beta users to the removal of FFT Filter that was in 1.2 and its incorporation into Equalization. It removed the confusion about "which should I use?". This is definitely an issue with having two volume changing effects (which of itself is I think somewhat untypical of most audio editors).
 * Alternatively, like a possible solution suggested for splitting the curves EQ and graphic EQ to two menu items, there could be two "Amplify" menu items with *matched design*. The one for scaling multiple channels or tracks is not available if you only select a mono track.


 * 19May11: On the proposal about a tooltip, I think the developers will be against lengthy tooltips, and I wonder how easy it would be to really explain in an acceptable length tooltip. I still agree with Ed's view that the real long-term answer is a (single) Help button in all dialogues going to the Manual. But if we want to suggest a tooltip in this proposal, we must I think suggest the text, or drop the idea.

Feedback from Steve Daulton
Probably the *most* important distinction between "Amplify" and "Normalize" is that "Amplify" changes the level *by* an amount whereas "Normalize" changes the level *to" an amount.

When processing a single track, this distinction is subtle, but for multiple tracks the distinction is totally obvious.

Use case 1: Multiple tracks from an album have been imported. The user wants to change the level so that they all have the same peak level. The way to do this is to "Normalize" the tracks to the desired level.

Use case 2: A multi-track project - several tracks that will be mixed down to a single "song". The user wants to change the level of all tracks so that the entire mix is at a different level but without changing the balance between tracks. The way to do this is to "Amplify" the tracks by the same amount.

Providing an option to "Normalize based on the peak level of all tracks" totally confuses the functions of these two distinctly different effects.


 * Gale: I don't see the "target" or "scale by" distinction as the primary one between Normalize and Amplify. Normalize was designed to also be different because it operated independently on each track or channel. I think both distinctions are important. The problem is that users with some knowledge assume/expect that "Normalize" will do what is in the feature request. Personally I would like freedom to do any combination of scale up/use target/per track or channel/per loudest track or channel.


 * Steve: Just two different ways of saying the same thing. If tracks are "scaled by" the same amount, then tracks are processed collectively. If tracks are amplified to a "target", then they are processed independently. The "New Peak Amplitude" in the "Amplify" effect is IMHO a little misleading as it can easily be misunderstood as being a (per track) target, which it isn't. There's probably a better description for that setting that makes it clear that it refers to the highest peak in one of the selected tracks, but I not thought of better wording. A tool-tip could help.

An important issue is that use case 1 is impossible without the risk of unbalancing stereo tracks. Currently the only way to achieve the desired effect for user case 1 is the arduous job of applying "Amplify" to each track individually and resetting the "New peak level" each time (if any value other than 0 dB is required).


 * Gale: I suppose this could be a third option in Normalize, so at least we get a new feature out of all this. Or are you suggesting the only choices for Normalize should be "as now" or "link stereo pairs" (one after the other if there are multiple stereo pairs)? In other words you cannot do what is in the feature request with Normalize if you have mono tracks?


 * Steve: I'm not sure what you mean Gale. As I see it, the options in the Normalize effect should be "Link Stereo Channels" which is selected by default (alternatively an option for "Normalize Stereo Channels Independently" - NOT selected by default). This would mean that the default option would treat one stereo track as one track and not as two independent channels. The behaviour with mono tracks would not be changed.
 * We do gain a new feature, and that is that multiple tracks can be Normalized in one go without damaging the stereo mix of any selected stereo tracks.
 * I strongly disagree with the second element of the old feature request: "When multiple tracks are selected, only the highest peak level of ALL tracks should be considered to adjust each track by the same amount so that the volume of each track relative to each other will stay the same" as that is exactly what the "Amplify" effect does. It is both unnecessary and confusing to duplicate that feature into the "Normalize" effect.
 * Gale: Thanks, Steve. I honestly don't think the original proposal was clear enough, but hopefully it is now. As for "When multiple tracks are selected, only the highest peak level of ALL tracks should be considered" being implemented in Normalize, I agree this is undesirable. I've revised my comment underneath in Feature Requests to reflect that. It *is* what people have said/apparently voted for, but I suspect at least some of them are mixing up "track" with channel or only considering the case where Normalize deals with a single stereo channel. I'll get hold of as many people as I can, which might change the voting somewhat. I've added five votes (you, Bill, Peter, me, Ed) for:
 * Normalize stereo channels independently: If unchecked, this normalizes any stereo tracks as a unit, retaining their channel balance while still letting all tracks be normalized independently to the requested level.