User:Billw58/Tracks and Clips

An important part of an Audacity audio track is the waveform display which gives a visual indication of the sound contained in that track. Stereo tracks can be split into two single-channel tracks and conversely two single-channel tracks can be combined into one stereo track. Each audio track is normally in one unbroken section, something like a single film clip. However, Audacity can split a track so as to create multiple clips within that track. Each clip in a track can then be moved around independently, but they all share several properties of the parent track such as its overall volume, panning, sample rate and sample format

The Waveform Display
The waveform display uses two shades of blue, one darker and one lighter.


 * The dark blue part of the waveform displays the tallest peak in the area that pixel represents. At default  zoom level Audacity will display many samples using only one pixel width, so this pixel represents the value of the loudest sample in the group.
 * The light blue part of the waveform displays the average RMS (Root Mean Square) value for the same group of samples. This is a rough guide to how loud this area might sound, but there is no way to extract or use this RMS part of the waveform separately.


 * [[Image:WaveAnnotated.png|image of waveform with peak and RMS regions indicated]]

If you zoom in far enough the light blue display will disappear, because there are not enough samples to provide a meaningful average in the region being displayed. The line you see now represents the peak level of the samples, that is the top of the darker part that you saw when you were zoomed out.

Below is an example of a dark blue only waveform, obtained by zooming in about 12 times. The waveform can now be clearly seen as joining together many individual sample points (the dots).
 * [[Image:TrackZoomedToSamples.png|image of track zoomed in to see the individual samples]]

Waveform (dB) view
The waveform display can be switched to a dB logarithmic  view by clicking on the track name (or the black triangle) in the  Track Control Panel.

The default linear Waveform display is very convenient for editing since the majority of audible work is on the screen. When zoomed in edit points are easy to find. However, the linear waveform doesn't correspond to the way your ears work--they sense quiet sounds more effectively. Halving the volume on the linear scale (for example, deamplifying a sound with a peak of +/- 1.0 by -6 dB to bring it to +/- 0.5 on that scale) doesn't sound all that much quieter. Human hearing would need a reduction of -18 dB to make audio "appear to sound" half as loud.

The following example is exactly the same recording as that above displayed in Waveform (dB) view.
 * [[Image:TrackExampleDB.png|image of track in Waveform (dB) view]]

A waveform with clipping
Below is an example of an oversaturated recording where clipping has occurred, that is, the signal has exceeded the maximum allowed level. The vertical red lines show where clipping has happened; these clipping indicators can be turned on and off (Audacity default setting is "off") by selecting View > Show Clipping.


 * [[Image:TrackExampleClipping.png|image of stereo track showing red clip indicator lines]]

Resizing Tracks
Click and drag between the two waveforms to change their relative height. Changing the height of the channels in a stereo track: Click and drag between the channels.
 * [[image:DragBetweenTracksStereo.png|Example of resizing the channels of a stereo track]]

Changing the height of a track: Click and drag between the tracks.
 * [[image:DragBetweenTracksMono.png|Example of resizing a mono track]]

Splitting and Joining Tracks
Using the Track Drop-Down Menu you can:
 * Split a stereo track into separate tracks for left and right channels
 * Split a stereo track into two separate mono tracks
 * Join two mono, left or right tracks into one stereo track

Here is a stereo track:
 * [[image:Split_Before.png|Stereo track before splitting into two separate tracks]]

After selecting "Split Stereo Track" from the Track Drop-Down Menu we get separate left-channel and right-channel tracks:
 * [[image:Split_Stereo_After.png|Stereo track after splitting into left and right tracks]]

After selecting "Split Stereo to Mono" from the Track Drop-Down Menu on the original stereo track we get two separate mono tracks:
 * [[image:Split_Mono_After.png|Stereo track after splitting into two mono tracks]]

Selecting "Make Stereo Track" from the Track Drop-Down Menu of the upper track of a pair of mono, left or right channel tracks (in any combination) will combine those two tracks into one stereo track. The upper track will become the left channel of the stereo track and the lower track will become the right channel regardless of their current designation as mono, left or right. In the example below, two mono tracks are about to be combined into one stereo track. The result of this operation will be to re-create the stereo track as shown in the image above.
 * [[image:TDDM_MakeStereo.png|Two mono tracks about to become one stereo track, with track drop-down menu pulled down to show option]]

When joining two single-channel tracks into one stereo track be aware that: Because of this, it is recommended that when you intend to join two single-channel tracks into one stereo track using Make Stereo Track that you leave the gain and pan settings of the two tracks at 0 and do not apply an envelope to either track.
 * Any gain and pan settings applied to the lower track will be retained until any adjustments are made to the gain and pan settings of the new stereo track
 * Any gain and pan settings applied to the upper track will be applied to the stereo track
 * Envelopes will be retained for the left and right channels of the new stereo track but any further envelope adjustments will be applied to both channels simultaneously which may give unexpected results

Reversing stereo channels
To quickly reverse the left and right channels of a stereo track:
 * Select Split Stereo Track
 * Drag the lower of the two resulting mono tracks above the upper track
 * From the Track Drop-down Menu of the upper track select Make Stereo Track

Applying equalization to one channel of a stereo track
Assume that you have a recording where one channel is "muffled" - lacking in high frequencies compared to the other channel.
 * Select Split Stereo Track
 * Click in the Track Control Panel of the muffled track to select it
 * Choose Effect > Equalization and apply the appropriate equalization curve to the track
 * Listen to the result - if it is not right, choose Edit > Undo Equalization and try a different equalization curve
 * When you are satisfied with the result, select Make Stereo Track from the Track Drop-down Menu of the upper track

Reducing the "width" of a stereo track
Assume you have a recording of a drum kit where the stereo spread of the kit sounds unnatural. The high hat sounds like is coming from the right speaker only and the floor tom from the left speaker.
 * Select Split Stereo to Mono
 * Adjust the pan control of the upper track to 70% left
 * Adjust the pan control of the lower track to 70% right
 * Listen to the result and adjust the pan controls until you get the effect you want
 * Select the two tracks
 * Click in the Track Control Panel of the upper track, then shift-click in the Track Control Panel of the lower track
 * Choose Tracks > Mix and Render
 * The two tracks are mixed and rendered into one stereo track
 * Note that if you had instead selected Make Stereo Track from the Track Drop-down menu of the upper track you would have lost your pan settings

Clips
A clip inside a track is a separate section of that track which has been split so that it can be manipulated somewhat independently of the other clips in the track. For example, you can split an interview into separate clips for each sentence then move them around individually although they are all on the same track. Or you could move a clip to another track that is panned further right, or split it to a new, empty track. The new track only contains that single clip, so again you can only move that whole track unless you split it into multiple clips.

Splitting a track into clips
Note that the term split is used to mean two different operations depending on the context. Above we used "split" to mean "split a stereo track into two single-channel tracks". In this section "split" means "split a single audio track into multiple clips". When you record some audio or import audio from a file, you get a single track. In many cases, there are natural gaps in the audio - silence between sentences or pauses between phrases in music. Those are good candidates for splitting the track into multiple clips, allowing you to move or otherwise manipulate those clips independently. There are eight ways to create multiple clips in a track:


 * Edit > Split at the cursor or region in an existing track or clip, doing nothing except separating it into multiple clips.
 * Edit > Split Delete at a region in an existing track or clip, removing the selected audio without shifting the following audio
 * Edit > Split Cut at a region in an existing track or clip, removing the selected audio to the Audacity clipboard without shifting the following audio
 * Edit > Split New at a region in an existing track or clip, moving the selected audio to the same position in a new track at the bottom of the project
 * Edit > Detach at Silences at a region in an existing track or clip, creating clips either side of absolute silences
 * Edit > Paste from the Audacity clipboard into vacant space in an existing track
 * Generate some audio into vacant space in an existing track
 * Drag a clip from a different track (or the whole track) into vacant space in an existing track using Time Shift Tool

As an example, the "before Split " and "after Split" images below show that after selecting Edit > Split, the two boundaries of the gray selection region are overlaid with a solid black split line, marking the boundaries of the three resulting clips.


 * [[Image:SplitBefore.png|Gray selection region before Split]]


 * [[Image:SplitAfter.png|Gray selection region after Split showing dark black split lines]]

Merging or joining clips
Unlike cursor points or selection regions, split lines representing boundaries between clips persist in the waveform of the track until the clips are merged or joined back into one clip.

An adjacent pair of clips may be "merged" into one clip by clicking on the split line to remove it. You can perform a similar "join" action without a mouse by selecting across one or more split lines then using Edit > Join to remove the split lines so as to make one clip.

Time-shifting clips
To move clips around independently, use the Time Shift Tool. When you click on a clip and drag it to the left or right, this is called time-shifting because you are changing the time at which that audio will be heard.
 * [[Image:SplitMove.png|Moving a clip after splitting a track into different tracks using Split.]]

If you click outside a selection area when dragging clips with the Time Shift Tool, the selection area will remain where it was as shown above. Otherwise, the selection area will move with the clip(s).

To move multiple clips at once, select all of the clips you want to move using the Selection Tool, then use the Time Shift Tool to click and drag within the selection area - all selected clips will move together (see before and after figures below).


 * [[Image:ClipsMoveTogetherBefore.png|Creating a selection so you can move multiple clips at once]]


 * [[Image:ClipsMoveTogetherAfter.png|After moving two clips together]]

Note that moving clips also makes use of guides, also seen in the chapter on Audacity Selection. When you move a clip, Audacity will snap the left or right boundary of a clip to the nearest edge of a clip in any other track, making it very easy to line up clips during editing.

Time-shifting stereo clips
In most cases time-shifting a clip in a stereo track will work exactly the same way as in a mono track. Most stereo tracks will have continuous audio in both channels and time-shifting a clip will move both channels equally.

Here is an example of a "standard" stereo track:
 * [[Image:TimeShiftStereo01.png|A standard stereo track with audio in both channels]]

When you time-shift a clip in this track, both channels move together:
 * [[Image:TimeShiftStereo02.png|Time-shifting a clip in a standard stereo track]]

However, there may be times when you will have a stereo track containing separate clips in each channel.

Here we see two mono tracks with multiple clips in each track:
 * [[Image:TimeShiftStereo03.png|two mono tracks with multiple clips in each track]]

After selecting "Make Stereo Track" from the Track Drop-Down Menu in the upper track, we get this:
 * [[Image:TimeShiftStereo04.png|stereo track with separate clips in each channel]]

Here we have positioned the Time Shift pointer over the first clip in the left channel of the stereo track:
 * [[Image:TimeShiftStereo05.png|ready to time-shift the first clip in the left channel of the stereo track]]

After dragging with the Time Shift tool, the clip in the left channel has moved independently of the clips in the right channel:
 * [[Image:TimeShiftStereo06.png|after time-shifting the first clip in the left channel of the stereo track]]

If you click in the area where the left-channel and right-channel clips overlap the two clips will move together.

Moving a Clip Between Tracks
The Time Shift Tool can also be used to move a single clip between tracks, but there must be room for the clip between the clips on the second track.


 * align=center|Getting ready to drag a clip from the first track into the second track.
 * [[image:Clips017a.png]]
 * align=center|The clip does not fit between the two clips on the second track.
 * [[image:Clips017b.png]]
 * align=center|The clip does fit in after the second clip the second track.
 * [[image:Clips017c.png]]
 * }
 * [[image:Clips017b.png]]
 * align=center|The clip does fit in after the second clip the second track.
 * [[image:Clips017c.png]]
 * }
 * [[image:Clips017c.png]]
 * }

Note: If a clip contains a selection area and you click with the Time Shift Tool within the selection area Audacity will not let you drag the clip into another track. To drag a clip containing a selection area into another track, either click in the track with the Selection Tool to remove the selection, or click outside the selection area (but still inside the clip) when dragging.