Long story short, is it possible for avconv to reduce the dimensions of a video by a percent? In my case, 50% smaller.
If the original video is 1280x720, I would like the output to be 640x360.
If the original video is 1024x768, I would like the output to be 512x384.
... and so on.
Is there a single generic parameter I can use that would allow me to automate the process in a script?