How do I set the first and last frame of a video to be an image?

HTML 5 implementations are different across various browsers. In firefox, the image specified by the placeholder attribute will be shown until the user clicks play on the video. In chrome, the placeholder image is sh开发者_如何学Goown until the video is loaded (not played), at which point the first frame of the video is shown.

To reconcile this issue, I would like to set the first frame of the video to the placeholder image so that the experience will be the same in both browsers.

I would preferably do this using ffmpeg or mencoder. I have very limited experience using these however, so if someone could point me in the right direction, I would be much obliged.

Thanks!