Fades

From Audacity Development Manual
Revision as of 13:33, 6 January 2013 by PeterSampson (talk | contribs) (changed the intros to plan text as Bill & Ed suggested)
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Peter 14Nov12: created this page.
  • Once Steve's Wiki page on fading is published I would anticipate that we would link to it from this page.
  • Gale: 14Nov12: It's a bit bare bones, and mostly duplication of the Effects page (apart from the images). Is there any more we can say? Something about what fades may be useful for? If/when we get Adjustable Fade shipped, would it go here? I am not sure it would. Perhaps this page should be for "automatic" fades?
    • How about an image of Cross Fade after mixing, to show what we mean by equal volume after the mix?
    • I can't see the point repeating the tips box both here and on the Effects page. I would suggest only having it here, if we want this page.
  • Peter 15Nov12: Yes it is a little bare bones, but I was deeply conscious that this is the Manual and that thus here we need basically state what the commands do rather than how to effectively use them (in line with the documentation of the other effects). Use of the fade commands is complex tutorial material and I was intending to point this page at Steve's nascent tutorial on Steve's use of fades tutorial (which is currently under development in the Wiki but could IMO earn a useful place as a tutorial in the manual).
    • Personally I find it useful to see the images of the various fades together on this page for easy visual comparison and I would hope that other readers would find that similarly useful. I was careful to keep the images and fades visually constant to facilitate such comparison.
    • I have added an "After Cross Fade" image as you suggested - though I'm not entirely convinced of its utility here (see comments above re tutorial material).
    • I agree that it's not worth repeating the note box on Effect Menu and here, so I have commented it out there for now. The note box here has slightly more information than the Effect Menu one - one extra bullet point.
  • Bill 05Jan13:
    • It seems we've reversed the normal usage of note and intro templates on this page. The page starts with a note at the top, then uses intros after each major heading. Regardless of the colour of the box, surely "tips" should not be at the head of the page? Tips ("semi-tutorial" material) have usually gone at the end of a page or section.
    • If we feel this page needs an intro, would it make sense to introduce the fact the Audacity ships with several "types" or "flavours" of fade effects?
    • In this case I am minded to agree with Ed, and would prefer the introductory paragraphs to be plain text.


Fade In/Out tips:
  • By repeating a fade in, the audio will remain quiet for longer then rise more rapidly to the original level. Similarly, repeating a fade out will cause the level to initially drop more rapidly then tail off at a lower level. As with other effects, the fade may be repeated as required by pressing CTRL + R.
  • For a more customizable exponential fade in or fade out, use the Envelope Tool on Tools Toolbar.
  • When cross-fading, fade in the first two-thirds of the overlapping audio that is beginning, and fade out the last two-thirds of the overlapping audio that is coming to an end. Two-thirds is a guideline rather than a rule, but helps to keep the level of audio constant through the fade. Alternatively, cross-fade using the two Cross Fade effects, selecting the entire overlap.
  • Typically fade-outs are applied over a longer period (up to ten seconds) whereas typical fade-ins are much shorter (less tha a second).

Linear Fades

These basic fades apply a fade to the selected audio, so that the amplitude changes gradually from the original amplitude at the start of the selection down to silence at the end of the selection. The shape of the fade is linear. The rapidity of the fade-out depends entirely on the length of the selection it is applied to.

Fade Out

Accessed by: Effect > Fade Out
Example of a linear fade out applied to a constant frequency and amplitude sine wave.

Typically a fade out would be applied over a longish audio selection, from one or two up to about ten seconds or so.

Fade In

Accessed by: Effect > Fade In
Gale: Then why not an image of a fade in with a shorter selection than fade out? It lets people see the difference the selection length makes.
  • Peter 17Nov12: I thought long and hard about this before I constrcted the images. I finally decided that the most important thing on this page was to document the effects themselves rather than their usage (that to me is tutorial material as in Steve's emerging Steve's use of fades a referenced above) - accordingly I wanted the users to be able to directly visually compare the fade shapes. Note too that there is actually no timeline/timebase in the images,so the fade length is not specified directly in the image.
    • Gale: Not a big deal, but I am not entirely convinced. "Unlike fading out a fade in is normally applied over a very short audio selection (less than a second)" is surely itself "tutorial material" (and is "less than a second" correct?). I agree it's good to let users compare like with like, but if you choose to introduce the comment about what the fade in is used for, it's confusing to then have the selections the same apparent length, timeline or not. Maybe have an additional image to show the difference the length of selection makes?
Example of a linear fade in applied to a constant frequency and amplitude sine wave.

Unlike fading out, a fade in is normally applied over a very short audio selection (less than a second). You may get an improved result by applying a fade in to the same audio selection three times (which effectively gives an exponentially curved fade in).


Cross Fades

Despite the names these effects do not do an automatic cross-fade between two tracks or clips. Instead they apply a curve that is different from the one used by the Fade Out effect. The curve used is one that will result in equal volume throughout the fade once the faded in and faded out regions are mixed.

Cross Fade Out

Accessed by: Effect > Cross Fade Out
Example of a cross fade out applied to a constant frequency and amplitude sine wave.

Cross Fade In

Accessed by: Effect > Cross Fade In
Example of a cross fade in applied to a constant frequency and amplitude sine wave.

After a Cross Fade

If the two waveforms above (Cross Fade In and Out) were mixed together then an equal volume section of audio would result as below. The example is untypical as we have used a constant frequency and amplitude sine wave to illustrate the fades - normal audio would appear more spiky.

Example of a constant frequency and amplitude sine wave after cross-fading.


Gale 01Jan13: Probably we should not have a "Muscial Fades" (plural) section until we have Pro Fade Out released on Wiki (or in 2.0.x)
  • Peter 1Jan13: I added a temporary H1 "Additional Shaped Fades" until we can un-leash "Musical Fades". SFO and AF are not part of "Crossfades" so need their own umbrella header.

Musical Fades

These fades apply a more musical fade to the selected audio, giving a more pleasing sounding result.

Additional Shaped Fades

Studio Fade Out

Accessed by: Effect > Studio Fade Out
ToDo-1 Gale 01Jan13: This is confusing. Which of the mirrored S or 1/2 period curves does it use, when? Or are they the same thing?
  • Peter 1Jan13: I changed the description to that on the Effect Menu page. Previous text was "Produces a smooth and musical sounding fade out. A mirrored S-curve or 1/2 period cosine is used for the volume and a linear ramp for the low pass filter (from 22050 Hz down to 100 Hz)."
  • Gale 02Jan13: It's up to Steve if he wants to explain about the curves, but I think it is un-necessary detail on this page. Removed "professional" in favour of "studio". "Professional" is too contentious, as Vaughan says.
    • Peter 4Jan13: I softened the description by moving the techy details into a tech-note rather than having them up-front first in the desciption - this should enable us to demote the P1 to >P2.

Produces a smooth and musical sounding fade out by fading out the higher frequencies a little quicker than the lower frequencies. It gives it a "going off into the distance" type of sound rather than sounding like a "mechanical" fade out. This technique has found favor in the recording studio for CD and LP tracks.

Example of Studio Fade Out applied to a constant frequency and amplitude sine wave.
Technical note: this effect works by applying a sinusoidal fade with a progressive low pass filter from full spectrum at the start of the selection to 100 Hz at the end.
Gale 01Jan13: ToDo Pro Fade Out has been committed for 2.0.3 as "Studio Fade Out", but as yet we have no Studio Fade In ready to release.

Studio Fade In

Accessed by: Effect > Studio Fade In provided you have installed it.
Example of a musical fade in applied to a constant frequency and amplitude sine wave.


Adjustable Fade

This has a dialog box where you can choose the shape of the fade in or fade out to be applied. You can also create fades to and from other than silence or full volume. An example of this might be a fade in from 20% of the original volume to 80% of the original volume.

ToDo-2 Gale 01Jan13: Adjustable Fade has been committed for 2.0.3. Review if this should go at the bottom of this page and the text here.


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