After you’ve captured your video, the next step is to trim away all those sections not wanted in the final project. One software that I use for this task is ScreenFlow by Telestream Inc. It’s easy to use and therefore you get the job done quickly. ScreenFlow is a screencasting and screen recording software.

Let’s walk through the process of trimming a few good clips from a playback recording of an iPad storybook app. When I used the Reflector software to record the book app, I recorded it from start to finish. Now that I have a better idea of what I want to include in my book trailer, I can trim away the unwanted footage.

Because the video will be used in a trailer for the book app, another decision to make at this stage is the size of the app in the book trailer window. I also want to use a png overlay of an iPad, which will take up some space in the trailer window. So I tested the png in the window and decided that I needed the playback of the app to be 680 x 510 pixels.

1. From the Menubar, click File - New Empty Document.
   
   
2. Next, click Insert - Choose and select your video footage. ScreenFlow will import your video onto the canvas (preview area). You might notice that the size of the canvas is not the same as the size of the video and you have a black background over the empty area. That’s fine because we will be cropping this away.
   
   In our example, we will first reduce the size of the iPad video by scaling the playback window down to 680 x 510 px that we decided upon for the trailer. Then we can crop away the extra space around that playback area.
   
   
3. Select the video in the preview area and scale it to the needed size.
   
   
4. Under the preview area you will find the Canvas controls. Click on the Crop tool and put the 680 x 510 px width and height values into the boxes that appear to the left. Then click the Apply button. This will remove everything but the video playback.
   
   Now that the playback is in the right size, we can crop some of the footage.
   
   
5. Move the Scrubber along the Timeline until you get to the start of the footage that you wish to keep. To trim away the unwanted beginning footage, click the red button at the bottom of the Scrubber. You will see that your footage is now in two sections.
   
   
6. Right-click on the left section (unwanted section) and choose Cut.
   
   
7. Click on the section that is left and drag it to the beginning of the Timeline.
   
   
8. Repeat this until you only have the sections of the playback footage that you wish to use in your trailer.
   
   
9. Save your project.
   
   Now we can export each section as a separate QuickTime movie.
   
   
10. Place the Scrubber at the beginning edge of a section. Hold down the Shift key as you drag the Scrubber to the end of that section. You will see a blue overlay indicating that the section is selected.
    
    
11. From the Menubar, choose File - Export Selected Range.
    
    
12. In the Export window, choose the Web - High Preset for an HD QuickTime movie.
    
    
13. Set the dimensions to Scale by 100%.
    
    
14. Click the Customize button and put the following values in the Movie Settings.
    
    Video Settings
    Compression: H.264
    Compressor quality Best
    Encoding Best Quality (Multi-pass)
    
    Sound Settings
    Format: AAC
    Sample rate: 44.100 kHz
    Channels Stereo
    Bit rate: 320 kbps
    
    

ScreenFlow screenshots used by permission of Telestream.