<< Click to Display Table of Contents >> Navigation:  Subtitling > Shot Change Detection

The detection algorithm is automatically started when a new video file is opened or imported. The detection works in background and you can still use EZTitles while the video file is processed. When finished the collected shot changes data is stored in a file so the movie is not processed again next time you open it. The default location for the shot changes data file is the video file's folder but you can change it using the Preferences dialog. The data file is named as the video file followed by "~shots.dat" suffix.

The shot changes are displayed on the timeline with yellow vertical lines and thumbnails below the audio graph. You can show/hide the thumbnail track using "View/Timeline" menu.

The shot change detection features are activated when EZTitles is installed. If you don't intend to use these features you can turn them off by using the Preferences dialog.

Snap to Shot Changes

Often when creating subtitles or closed captions there are requirements that the subtitles appear/disappear on the shot change boundaries.

One of the truly remarkable features of EZTitles is the automatic snap to shot changes during the timecoding. And there are also tools that allow you to fix already created subtitles.

First you need to activate the snap functionality from the Project Settings. There is also a threshold value in frames.

During the spotting if the captured timecode is less than the "threshold" frames from the shot change, it is automatically snapped.

Snapping Rules

There are two parameters in Cues section in Project Settings that controls the snap behavior. They are "Before Cut" and "After Cut" frames.

The out-cue is placed on the selected number of frames before the shot change and the in-cue is placed after the shot change.

please note that the rule for the minimum interval is applied first.

So after the snap, if the next in-cue is closer than minimum interval frames from the previous out-cue it is moved forward to meet the minimum interval.

Here is an example that illustrates how the snap works:

Suppose that the minimum interval is 4 frames, "Before Cut" parameter is 2 frames and  "After Cut" is 1 frame. If there is a shot change at timecode 10:00:00:10 then:

▪If the subtitle is not chained with the next one and you are setting the out-cue it will be snapped 2 frames before the cut i.e. 10:00:00:08;

▪If the subtitle is not chained with the previous one and you are setting the in-cue it will be snapped 1 frame after the cut i.e. 10:00:00:11;

▪If you have already set the previous out cue to 10:00:00:08 and you are setting the in-cue it will be snapped 4 frames (minimum interval) after the previous out-cue i.e. 10:00:00:12.

Commands involved

Activating the automatic snap to shot changes affects the behavior of the following commands in both Edit and Preview modes:

Num Enter – Sets the timecode of the current frame as In-cue value for the current subtitle.

Num Ins – Sets the timecode of the current frame as Out-cue value for the current subtitle.

Num Del – Sets Out-cue value from the current time-code and the next subtitle In-cue at default interval (see Edit/Presences/Command Options).

New three commands are introduced that alter the automatic snap to shot changes parameter. If the automatic snap to shot changes is switched on, these three commands set the cues without snapping and if it is off they are used to force the snap.

Shift + Num Enter – Capture current subtitle In-cue and override the "Snap to shot changes option".

Shift + Num Ins – Capture current subtitle Out-cue and override the "Snap to shot changes option".

Shift + Num Del – Sets the Out-cue value from the current time-code and the next subtitle’s In-cue at default interval and overrides the "Snap to shot changes option".

There are also commands for unconditional snap:

These commands don't have keyboard shortcuts assigned by default. If you want to use them you can assign suitable shortcuts using the Customize options. The commands are located in the Time Code category.

Shot Changes Toolbar

You can navigate through the shot changes using the two most left buttons.

The other two buttons are intended to insert or remove a shot change. The modifications are automatically stored when you save your project (.ezt file).

Shot Change Detection Options

It is not so uncommon for a video material to have black stripes above and below the picture. As in a letterboxed video file for example. Those black stripes significantly reduce the accuracy in detection of a shot change, which makes the subtitler's job complicated. They have to be dealt with care and that is why two new options are introduced on the Video/Shot Change Detection menu: