The Time feature considers the entire clip on the Timeline, not just the portion you select, resulting in frames from parts of the clip that you did not choose appearing in the speed-adjusted section.  You can export a project’s section to adjust the playback speed to a separate video file to work around this issue.  After you change the playback speed of the individual video, import it into your original project as a new clip.  The following steps demonstrate how to adjust the playback speed of a section of your clip: 
1.  Export the section of your project where you want to adjust the playback speed.
1.  Right-click the clip to export, then select the Properties option.
2.  In the Properties window, scroll down the table to the Frame Number property.
3.  Right-click the value next to Frame Number (default value is "None") and select "Timeline."
4.  Move the play-head (the red vertical line on the Timeline) to the first frame of your selected clip.
5.  Take note of the number in the upper left-hand corner of the preview screen, the first frame.
6.  Move the play-head to the last frame of your selection.
7.  Take note of the number in the upper left-hand corner of the preview screen, the last frame.
8.  Move the play-head to the first frame of your selected clip.
9.  Right-click the value next to Frame Number and select "None" to turn off the frame numbers displaying.
10.  Click the "Export Video" button (the small red circle icon) in the toolbar at the top of the Main window to open the Export Video window.
11.  Enter a new name for the exported section into the File Name: field.
12.  Enter a destination folder for the exported section into the Folder Path: field.
13.  On the Simple tab:
1.  Review the Target, Video Profile, and Quality settings. 
(Ensure the Target, Video Profile, and Quality Settings match the source clip.)
14.  On the Advanced tab:
1.  Change the Start Frame to the clip's first frame.
2.  Change the End Frame to the clip's last frame.
15.  Click the Export Video button to export only the selection of your project.
2.  Create a new project and import only the clip to adjust the playback speed.
3.  Change the speed of that clip, then export it as another video file.
4.  Import the recently modified clip to your original project and add it to the Timeline.
The method above uses the clip's Right-click Menu, which has preset values.  If you don't want to use the preset values (possibly incurring the glitches), you can perform the calculations yourself and manually enter the values in the Time property of your clip.  Here is a description of the Time property and how to manipulate the values:


The Time property allows you to change the speed at which the clip plays – forward, backward, or both. It allows great flexibility and relies on the animation system.


The Time value represents the frame number playing at this keyframe position. If you did not set Time keyframes, the default values are 0 or 1, and the clip will play at regular speed. If you set Time keyframes, OpenShot will render the video to change frame numbers smoothly between the keyframes.

You will often need to know how many frames there are in the clip. One way is to multiply the clip’s Duration by the project’s frame rate. Another way is to right-click the clip and set Time » Normal » Forward » 1x, which sets the start Time keyframe to 1 and the end Time keyframe to the last frame, which you can read by jumping to that keyframe. You can also jump to the end of the clip and note the time shown on the timeline (in the format hours:minutes:seconds:frames) and subtract the time displayed at the start of the clip, converting that result to the number of frames based on the project frame rate.

It may be easiest to give some examples. We’ll take a clip that is 40 seconds long, with a project frame rate of 30 fps. The clip therefore has (40 x 30 =) 1200 frames.
  • To slow the clip, so it lasts for 55 seconds, set the End property to 55 (so the clip’s duration is now 55 seconds), set a Time keyframe at the clip's start to 1, and the clip's End to 1200.
  • To speed up the clip, so it lasts for 30 seconds, set the End property to 30, set a Time keyframe at the clip's start to 1, and the clip's end to 1200.
  • To play the clip in reverse, set a Time keyframe at the clip's start to 1200 and the clip's end to 1. OpenShot renders the frames in order: 1200, 1199, 1198, 1197, etc.
  • To synchronize an event on the clip which happens at 15 seconds with an event in the overall video that happens 17 seconds after the clip starts, right-click on the clip and set Time » Normal » Forward » 1x. Note the frame number shown in the Time property at 15 seconds, and insert a Time keyframe at 17 seconds with that value. The clip will play slower until the synchronization point, then speed up to reach the end simultaneously, assuming the change in speed looks acceptable.
  • To pause the clip after 11 seconds for 3 seconds and then play the rest of the clip regularly, add 3 seconds to the End property.  Right-click on the clip, set Time » Normal » Forward » 1x, insert a Time  keyframe at 11 seconds, noting the value, and set a new Time keyframe at 11 + 3 = 14 seconds to that value. If your clip has audio, you might need to set Volume keyframes to 0 to mute the sound.
  • To play the clip halfway, then play it reverse back to the start, set Time keyframes at the beginning and the end to 1, and a Time keyframe in the middle (at 20 seconds) to 1200/2 = 600.
  • To play the clip and hold the last frame image frozen for another 5 seconds, add 5 seconds onto the End property; you don't need to set the Time property.
If you find that changes to clip speed are too abrupt, you can smoothen the transitions by choosing a bezier curve in the animation system. In the event of difficulties with this, you might need to create a second (duplicate) Time keyframe in the next frame.


A quick way to remove all Time keyframes is to right-click the clip and choose Time » Reset.


Note:
  • OpenShot does not intend for you to use the Time property with audio clips.  Any sound you adjust may have very noticeable distortion at a different speed.
  • Setting keyframes for Start and End properties will interact with the Time property. You may find the best method for adjusting video playback speed is to set Start to 0, with the End property  determining the clip’s overall Duration.  he Time property can control what is playing and how.