I just discovered that if you display the video screen image (eg,the picture from the internal PC camera), then put the mouse on the left margin and move it towards the right margin. The image diminishes down to zero size, but then keep moving the mouse to the right, moving the left edge of the image beyond the right edge. Lo and behold, it is flipped horizontally. Similarly, if you drag the bottom of the screen upwards beyond the top, it will be flipped vertically. Then you can drag it back onto the screen and resize it.