You can have Microsoft Expression Encoder create a thumbnail for your media file. Expression Encoder stores this thumbnail with the encoded file. This will be the representative thumbnail for your media file when you view the file in Windows Explorer, as well as being the placeholder image for Silverlight videos before they are cued and played back. Expression Encoder saves thumbnails by using the following naming convention:
You can also set a thumbnail to represent each Timeline marker. Timeline marker thumbnails can be used for visual navigation in Silverlight experiences, so they serve a different purpose than the thumbnails described in this topic. For more information, see Add markers.
To set a thumbnail
In the Media Content panel, select the video to which you want to add thumbnails.
If you cannot see the Output category, on the Window menu, click Output to open the Output panel. If the panel is open, but you cannot see it, on the right side of the application, click the Output tab.
Click the arrow next to Thumbnail and JobOutput to expand these categories.
In the Type section, select one of the following options for your thumbnail:
If you do not want a thumbnail associated with the video, select None.
To use the first non-black, non-solid color frame as the thumbnail, select Best Frame.
To use the first frame of the video as the thumbnail, select 1st Frame.
To choose your own thumbnail from the video, select Custom. When you select this option, a red thumbnail marker appears in the Timeline and you can either drag that marker to the frame you want to use as the thumbnail or, in the Thumbnail category, manually type a time code in the box.
Under Encoding, choose a compression method for the thumbnail. If applicable, drag the numeric value next to the menu to set a quality level. The higher the number, the higher the quality of compression.
Under Size, type a size for the thumbnail, or drag the values to set them. Drag the value up or right to increase it, or down or left to decrease it. To maintain the aspect perspective to the height value, select the Maintain Aspect Ratio check box.