Scrubbing and Seeking

Peter 05Jun16: ToDo-1 This page will require a major update for the revised GUI including pinned playhead - not to be updated until Paul's GUI changes stabilize and finalize.

• Peter 05Aug16 in an email note to James:

Although Paul has implemented some vast complexities, at its simplest it works quite well

1) get some audio

2) normal zoom or normal working zoom

3) Click on the visible, new (and thus discoverable) Scrub Play button

4) Waggle the cursor position about over the waveform

5) lo and behold you get 1x forward/backward scrubbing.

Things only start to get complicated when you discover the speed control when you accidentally nudge the mousewheel, when you toggle over into seeking - or when you pin the playhead and discover you get a different form of speed-controlled Scrubbing. Or when you play with turning the Scrub Bar on and off and wonder just why you need it at all.

• Gale replies 05Aug16:

I don't think it's immediately user-obvious that pinning the playhead is going to something else, though.

The whole thing is "see what it does and explore", rather than intuitive.

To which James and I both agreed.

Scrubbing is the action of moving the mouse pointer across a segment of the waveform to hear the audio - a convenient way to quickly navigate the waveform to find a particular event of interest.

The term "Scrubbing" comes from the early days of the recording industry and refers to the process of physically rotating tape reels to move the tape past the playhead to locate a specific point in the audio track.

Mac OS X users: In the below instructions, use COMMAND instead of CTRL. So for example, COMMAND + left-click starts scrubbing.

Scrubbing

Pressing CTRL + left-click will put you into scrub play mode. You can now release the mouse button then move the pointer right and left across the waveform. This will cause Audacity to scrub play forward or backward respectively from the point at which you clicked in the waveform. Nothing will happen until you move the mouse pointer.

Pressing the Scrub button in the Scrub Toolbar will put you into scrub play mode. Alternatively you can use the Transport>Scrubbing and select Scrub from the dropdown menu. The green playhead cursor will appear but otherwise nothing will happen until you move the mouse pointer. You can now move the pointer right and left across the waveform. This will cause Audacity to scrub play forward or backward respectively. Scrub play will temporarily stop when the green playback cursor (the "playhead") catches up with the mouse pointer but will restart again as soon as you move the mouse left or right. Once you have placed Audacity in scrub play mode it will remain in that mode until you Stop Scrub play which would then allow you to restart in normal play mode.

• Click the Scrub button again or the Stop button (or its shortcut SPACE) to stop scrub play at the current play position from where you mark that point (with a Label) or restart normal playback from there.

If instead you wish to retain your current cursor position or selection just use the ESC button to stop and exit from scrubbing

• The speed of scrub play can be controlled by rotating the mouse wheel (if your mouse is so equipped). The changed scrub speed will be shown temporarily in yellow-ochre superimposed on the track.

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

• You can invoke scrub play while audio is playing normally and it will abandon the playback to perform scrub play.

• For safety reasons. you cannot invoke scrub play while you are recording (or paused in recording mode).

Seeking

If you hold the left mouse button down as you scrub the scrubbing will change to seeking.

In seek mode many small slices of the audio are played (at normal speed even if you have changed speed). The playhead is always moved very close to the mouse pointer enabling you to move across the audio rapidly. This is similar to using the seek button on a CD player.

Releasing the left mouse button while seeking will return you to scrub play and to any changed speed you had selected. Holding left mouse button again will return you to seek play for quick navigation. With practice you will find it easy to repeatedly hold then release the left mouse button to switch between seeking and then scrubbing to focus on a particular area.

A single left-click anywhere in the waveform while scrubbing mode will immediately seek to that position. Scrubbing will not resume until you move the pointer again.

Scroll-scrub

If you CTRL + double-left-click then move the mouse pointer to scrub, the green play cursor (effectively the "playhead") remains at the mid-position of the waveform display and the speed of scrubbing can be varied much more smoothly by moving the mouse pointer.

In this mode the mouse pointer position does not determine the target location of the scrub, but determines the speed of the scrub. The further away you move the mouse pointer from the play cursor (in either direction), the faster the speed of the scrub. The current scrub speed is shown permanently in lime green, superimposed on the track as you move the pointer.

The speed of the scroll-scrub as determined by the mouse position can be varied by rotating the mouse wheel (if your mouse is so equipped). Move the wheel upwards to increase the speed or downwards to reduce the speed. This works at the same time as modifying the speed by moving the pointer left or right.

When scroll-scrubbing backwards, as play approaches the leftmost portion of the audio the green play cursor will move from a centered position to the left until it reaches zero and stops. If you turn on "Enable Scrolling left of zero" in Tracks Preferences then the play cursor will remain centered as you approach the leftmost portion of the audio. Enabling this preference makes it easier to scroll-scrub at slow speeds close to the start of the track.

Scroll-seeking

If you hold the left mouse button down as you scroll-scrub, scroll-scrubbing will change to scroll-seeking. The modified speed when scroll-seeking is indicated by an "X" at the end of the speed displayed in lime-green.

Releasing the left mouse while you are scrub-seeking will return you to scroll-scrub play and holding it again will return you to scroll-seek play.

If you quickly press and release the left mouse button when scroll-scrubbing, this jumps the time position of the midline in the current direction of scroll-scrub. The jumps are longer, the further the pointer is from the midline.