Scrubbing and Seeking

Peter 01May15: Very rough draft notes copied from Notes for Testers in the Wiki.

• Peter 20May15: Updated with Paul's revised UI - notes taken from Paul's email.

Scrubbing is an interaction in which a user drags a cursor across a segment of a waveform to hear it. Scrubbing is a convenient way to quickly navigate an audio file. The term comes from the early days of the recording industry and refers to the process of physically moving tape reels to locate a specific point in the audio track, this gave the engineer the impression that the tape was being scrubbed, or cleaned.

The transcription toolbar setting determines the initial scrubbing speed limit each time you start scrubbing (under discussion, subject to change).

Scrubbing

Scrubbing works only in Select tool mode.

Using the CTRL + left-click will put you into scrub play mode. When in this mode dragging the cursor right and left across the waveform will cause Audacity to scrub play forwards or backwards. Scrub play will temporarily stop when the "play-head" the green playback cursor catches up with the mouse cursor but will restart again as soon as you move the cursor in either direction.

The speed of the scrub play may be controlled by rotating the mouse wheel (if you have one).

Each 4-clicks of the rotated mouse wheel doubles, or halves the speed which is equivalent to one octave. One click of the mouse wheel is equivalent to 3 semitones.

It is possible to zoom while you are scrubbing by holding the CTRL key down and rotating the mousewheel.

Pressing the Stop button or its shortcut Space at any time will stop scrub play and return you to normal play and record mode. Alternative pressing CTRL + left-click when in scrubbing mode will also return you to normal Playback and Recording mode. The scrubbing position on completion can be marked with a left-click mouse gesture which moves the cursor to that position and then using CTRL + B to create a marker label at that point.

You can invoke scrub play while audio is playing normally and it will abandon the playback to perform the scrub play. You cannot invoke scrub play while you are recording or paused in recording mode. You can use the Pause button while scrubbing to pause and restart the scrub play.

Seeking

If you hold the Shift key down as you scrub the scrub speed setting is ignored. What is played back though at normal speed is many small slices of the audio and always something very close to the mouse cursor so there is no lag. This is similar to using the seek button on a CD player.

It is also possible to press and release Shift as you go thus alternating between scrubbing and seeking.

Stationary "play-head" scrubbing

Peter 21May15: ToDo-2 we have, as yet no proper nomenclature for this type of scrubbing. I think Paul calls it double-click scrubbing

If you CTRL + double-left-click then drag to scrub, the green play cursor (effectively the "play-head") remains at the midpoint of the waveform display and the speed of scrubbing can be varied much more smoothly by the position of the mouse cursor. In this mode it does not determine the target of the scrub rather it determines the speed of the scrub, the further away from the play cursor in either direction the faster the speed of the scrub.

Double-clicking also works with the Shift key held down and this makes it much easier to skip through the track at a uniform rate as the amount that you skip depends on the distance between the mouse and the "play-head" green play cursor which remains still. So you can easily move further from that line to accelerate , move back to decelerate and hold steady to skip at a constant rate.

Also notice changes to status bar messages and the Mouse Preferences dialog.