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 or Seeking is the action of moving the mouse pointer right or left so as to adjust the position, speed or direction of playback - 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.

Scrubbing

Clicking the Scrub button in Scrub Toolbar when stopped or using standard playback will put you into scrub play mode. Alternatively you can use the Transport > Scrubbing menu item and select Scrub from the cascading menu, or set a shortcut for Scrub in Keyboard Preferences.

On starting scrub, the green playhead cursor will appear but otherwise nothing will happen until you move the mouse pointer to right or left to play forwards or backwards respectively. Playback continues until the playhead in the Timeline reaches the pointer, and restarts when the pointer is moved again. If you keep moving the pointer slowly, this plays the audio slowly. If you move the pointer a long way from the playhead, this plays at normal (1x) speed.

Once you move the pointer, a scrub widget appears at the bottom of the Timeline . The widget shws as green left- and right-pointing triangles (similar to the Scrub button) and a vertical white line through the waveform follows the movement of the scrub widget.

The image below shows scrubbing taking place in default unpinned playhead mode. Note that the Scrub Play button is shown as depressed in Scrub Toolbar File:Scrub button depressed in Scrub Bar 60%.png to indicate that scrubbing is active. Also note that the green left/right pointing scrub widget is to the right of the green triangle playhead indicating that forwards scrubbing towards the pointer is taking place.

The image above also shows the Scrub Bar button in Scrub Toolbar is up (off). If Scrub Bar was enabled, the scrub widget would appear in Scrub Bar immediately below the Timeline, and could itself be dragged right or left by holding the mouse button down. This temporarily enables Seeking.

Gale 08Aug16: We are intending to show the standard Play icon during Scrub or Seek.

• Once Audacity is in scrub play mode it will remain in that mode until you explicitly stop playback (which then allows you to restart in normal play mode).
  • To stop scrub play and set the cursor at the current playback position, click the Scrub button again, or click the Stop button (or its shortcut SPACE). It may be useful to label that position for future reference. Alternatively click the Play button to restart normal playback immediately from the current playback position.
  • To stop scrub play without moving the current position of the editing cursor, use the Escape ESC button.

• The speed of scrub can be controlled by rotating the mouse wheel (if your mouse is so equipped). Each four steps upwards of the rotated wheel doubles the speed, and each four steps downwards halves the speed. This is equivalent to one octave of pitch change. The changed scrub speed will be shown for a few seconds in ochre text superimposed on the track. Changed speeds set by the mouse wheel are not remembered if you stop playback and restart Scrubbing.

• You can zoom while scrubbing or seeking by holding the CTRL key down and rotating the mouse wheel, or by using the zoom buttons in Edit Toolbar or their shortcuts, or by using the View Menu zoom commands.

Gale 08Aug16: Currently Scrub does stop recording, so commented out.

• Peter 08Aug16: so it does (I just tested) - but it bloomin' well shouldn't. I didn't used too aas far as I recall, that's why the 2.1.2 Manual says so. And we agreed a long time ago (Bill and I were adamant about this) that stuff like this should not interrupt a recording - so this is a bug that we should be logging (a regression). It could cause a user to lose/interrupt a valuable irreplaceable recording.
  • The 2.1.2 Manual clearly states on this page: " You cannot invoke scrub play while you are recording or paused in recording mode."
    • But yes this needs commenting out until we address this issue.
• For safety reasons. you cannot invoke scrub play while you are recording (or paused in recording mode).

Seeking

Seeking is similar to Scrubbing except that it is playback with skips, similar to using the seek button on a CD player. Even if you move the mouse pointer a long way from the current position of the playhead, the playhead will immediately move very close to the mouse pointer, letting you move across the audio rapidly.

Seeking with unpinned playhead is always at 1x speed. You can control the maximum seek speed with by mouse position and mouse wheel when you are in pinned playhead mode.

To enter Seeking or change from Scrubbing to Seeking, click the Seek button in Scrub Toolbar . Alternatively you can use the Transport > Scrubbing menu item and select Seek from the cascading menu. or set a shortcut for Seek in Keyboard Preferences.

When Seeking, the widget in the Timeline or Scrub Bar shows double left- and right-pointing green triangles similar to the Seek button in Scrub Toolbar. There is no need to drag the widget when in Seek - moving the pointer seeks in the same way as drag.

While Scrubbing or Seeking, you can still click in the track to set the editing cursor, or click and drag to make a selection. The point or region could then be labelled. For example, let the playhead reach the mouse pointer at the start of a region of interest. Then drag a selection which will play, stop dragging and release the mouse when you hear the end of the region you want, then label the selection.

Scrub Bar

Clicking the Scrub Bar button File:Scrub Bar button 60%.png in Scrub Toolbar makes Scrub Bar appear below the Timeline (or hides Scrub Bar when it is already enabled). Alternatively you can use the Transport > Scrubbing menu item and select Scrub Bar from the cascading menu, or set a shortcut for Scrub Bar in Keyboard Preferences.

Peter 08Aug16: ToDo-2 This image will need updating if the icon for the unpinned playhead changes.

File:Timeline with Scrub Bar.png

When Scrub Bar is displayed the green left- and right-pointing scrub or seek widget appears in Scrub Bar instead of at the bottom of the Timeline.

The key benefits of enabling Scrub Bar are:

• When scrubbing or seeking you can left-click anywhere in Scrub Bar to move the scrub or seek position to that point.
• When scrubbing you can left-click in Scrub Bar and hold the button down to temporarily change to Seeking. Once you release the mouse button then scrubbing will resume again, but from the point at which you stopped seeking.

Right-clicking anywhere in Scrub Bar displays a menu identical to that in Transport > Scrubbing where you can quickly start, stop (or change between) Seeking or Scrubbing or turn Scrub Bar off. Using this menu to change between Seeking and Scrubbing saves you having to move the pointer and so change the playhead position un-necessarily.

Pinned playhead Scrubbing and Seeking

Gale 08Aug16: ToDo-2 "pinned" below will need to be a link eventually.

• Peter 08Aug16: Yes, but I haven't written that page yet ;-)

If you use Scrubbing or Seeking with the playhead pinned in the center of the project window, so that playback constantly scrolls the track, the speed of scrub or seek playback behaves differently to when the playhead is unpinned.

In pinned playhead mode the mouse pointer position always directly determines the speed of scrub or seek. The further away you move the mouse pointer from the Timeline playhead (in either direction), the faster the scrub or seek. The current scrub or seek speed is shown permanently in lime green text, superimposed on the track. The default maximum scrub speed is +1.00 (for forwards play) and -1.00 (for backwards play), that is normal speed. The default maximum seek speed is +10.00 (for forwards play) and -10.00 (for backwards play).

The speed of scrolling scrub or seek 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. The maximum possible speed with the pointer at either edge of the window and the wheel at maximum speed is 32.00x for Seeking and 320.00x for Scrubbing. Changed speeds set by the mouse wheel are not remembered if you stop playback and restart Seeking.

A very useful setting for using scrubbing with pinned playhead is to move the pointer to the extreme right (100%) position and increase the maximum speed to 2.00x.

With this setting, when you move the pointer back to the 75% position on the waveform you will get normal speed forwards playback and at 25% position you will get normal speed backwards playback. Moving the pointer towards the center from there will give you gradually slower than normal speed and moving towards the right or left edges will give you gradually faster than normal speed up to your chosen maximum of 2.00x.

Peter 08Aug16: ToDo-2 This image will need updating if the icon for the unpinned playhead changes.

Image of forwards scrubbing at 1.00x speed having set a 2.00x maximum speed, waveform moving leftwards.