The video files are created from the frames that can be saved to the frames of an animated GIF, the image type that is frequently used on the web in a form of banners and short animations. Because the frames are saved uncompressed, it is useful only with shorter videos, otherwise the file size of animated GIF can be very large.
For example, to convert a short SWF file to the animated GIF to create an alternative for the users without a Flash plugin, we can use the command (the pixel format must be set to rgb24)
ffmpeg -i promotion.swf -pix_fmt rgb24 promotion.gif
The default resolution of the mptestsrc video source is 512×512 pixels, other listed sources have 320×240 pixels resolution. The most versatile is the color image source that is able to generate the image of any color and any size, for example to create a teal background for a leaderboard banner sized 728×90 pixels, we can use the command
ffmpeg -f lavfi -i color=c=#008080:s=728×90 leaderboard.jpg