Timebar + Preview Region Usage in the Compositor and Viewer

The Viewer and Compositor each have a timebar control area with a red indicator line below the video output. The timebar shows the whole time covered by the resource. When a video resource is loaded in the main window and you move in the compositor, the insertion pointer in the main window will reflect those movements. But in the viewer only that specific media is shown and there is no corresponding movement on the timeline.

Figure: The mouse cursor, above the green colored “play forward” transport button, is on the timebar. Further to the right we see the red "indicator line".
Image timebar1

Both the Compositor and Viewer support labels and in/out pointer which are dis- played in the timebar. And as with the movements, when you use the labels or in/out pointer in the compositor timebar, the result will also be reflected in the main window timebar. Along with that, of course, when you move to a label or in/out pointer in the compositor, the insertion point in the program window will go to that position.

The timebar in the compositor and the viewer covers the whole length of the resource loaded in there. Moving the mouse with the LMB pressed moves the position in the resources as indicated by the indicator line. A complete mouse movement between left and right edges of the window moves the indicator line by default along the whole timebar. With long resources it can be difficult to precisely locate sections in the resource. To make this easier, you can limit the effect of the same window-wide mouse movement to a smaller area of the timebar, this area is defined as the preview region. This region can also be moved along the timebar.

For instance, if you need to get a few 10 second clips from an 60 minute video, you could define a one-minute preview region, move it approximately to a place where a clip needs to be taken, and easily select with the mouse in and out points within the region, because the whole window mouse movement now covers 1 minute instead of 60 minutes.

To create and use a preview region, hold down the right mouse button inside the timebar on either end of the timebar close to the edge until you see the resize pointer. While continuously holding the right mouse button down, drag the arrow away from the end towards the middle of the timebar until you have the desired area outlined. The slider will be a dark red color while the selected preview region will remain the same initial black color. There are either a left or right resize pointer and you can click and drag in either direction to expand or shrink the region.

Figure 2.21: A left-facing arrow on the right side of the reddish slider bar is used to drag the bar.
Image timebar2

Figure 2.22: Here you can see the right-facing arrow used to drag the other end of the slider bar. The black area is the actual preview area.
Image timebar3

You can slide the preview zone left or right by holding the right mouse button over the preview zone where you will see a fat double headed arrow. The selected area will move left or right as you drag and still retains the same size.

Figure 2.23: Note the double-headed fat arrow in the black preview area used to move the selection over.
Image timebar4


  1. If no preview region is set, increasing the length of the media on the timeline by inserting media or appending, has no effect on the non-selected preview region. That is, you will not see the reddish slider bar suddenly mysteriously appear.
  2. If the preview region is set, when you replace the current project or file, the preview region is automatically disabled.
  3. If the preview region is set, when you append data or change the size of the current project, the preview region may appear to either move, shrink, or grow depending on the new length of the media on the timeline.
  4. To disable the preview region, you will have to drag both the right and the left blue slider bars completely to their corresponding end so that there is no longer any visible red slider.

A good method for taking advantage of the preview region is described here. On the main track canvas, scroll to the beginning of the area of interest. When you do that, you will see in the compositor the red indicator line of that location. Now in the compositor window, right mouse drag from the left side of the edge of the timebar to create the dark red slider bar line up to the red indicator. Back in the main track canvas, move to the location of the area you want to end looking and again you will see the red indicator line in the compositor. Use the right mouse drag from the right to stop at that end point. Using this method is often easier than continuous usage of the single frame move which can be tedious.

One last interesting item of note – sometimes you may wish to see just a little more that is outside the preview region and you can do so! You can actually move outside the compositor or viewer window space and view more, at least until you hit the end of the screen space.

The CINELERRA-GG Community, 2021