The following dialog appears when you click this toolbar button :
Settings can be updated for the shot sampler and the automatic shot engine.
Definition : the shot sampler linearly slices the video at a given rate, and never relies on the content of the video. The automatic shot engine intelligently slices the video based on its content.
Reasons why you would use the shot sampler :
Reasons why you would use the automatic shot engine :
Shot sampler settings
Although the settings look a bit complex at first sight, it's really simple. The shot sampler does its job based on the sampling rate. Because the sampling rate varies a lot depending on the size of video, some are very short (trailers), some are very long (full movies), and because users may wish to choose a rate with absolute or relative figures, there is an option to choose from.
By default, this option is the fourth, which means that once the shot sampler is started it will extract and create one shot every 40 frames of video, which for most videos roughly equates to 1 shot every second.
If you replace 40 with 200, then you'll notice that 5 less shots will be extracted and created.
Because the way you expect shots to be produced may depend on how you see video clips, you can choose another option, among which :
Automatic shot engine settings
The automatic shot engine has only one param to tweak, and even that param should mostly never be. The param is a threshold. The greater, the less sensitive is the shot engine, and as a consequence the less shots will be extracted out from the video. The default value of 12 is just about the best compromise for videos on one hand, regardless the content, the file format or even the rendered color depth (videos looks less grainy if you are in 24-bit display mode rather than 16-bit mode).
You can always reset the settings for the entire dialog box by clicking the
A nice thing about the shot settings is that they are always kept in sync with the internal engines. Thanks to this, you can start a shot engine, then pause it, change the shot settings, click OK, and then resume the shot engine. Typically, pausing and resuming is done by hitting the space bar.
This Try-and-resume feature is especially useful for the shot sampler. Depending on the size of the video, the rate of sampling may be totally inappropriate, too low or too high. The automatic shot engine's default setting has been however tested for many types of video, and thus should be ok for all videos. There is no reason in practice to change it.