Use these calls to add, modify and delete a watermark images. A watermark is a GIF, JPG or PNG images that can be burned into the different conversions of a video or embedded into the video player. Watermarks are generally used to add some branding to and discourage redistribution of plain video files or embedding video players on other web sites.
The best choice for a watermark is a PNG image, since PNG supports transparency. This makes the watermark blend nicely with the video.