[FFmpeg-user] Make ffplay accept hotkeys while playing audio only

[Szilágyi Zsolt]

This is a feature request. ffplay is really a convenient tool which is
preferred (I think) for its simplicity and low recources' demand. However,
there is an annoying thing that reverses the last statement. When playing
only audio, a window is forced showing rdft or waves. Well, without this
window (with "-nodisp" option) ffplay's CPU usage is almost 0 and with the
window is between 2-5%. So, if we do not need that visualisation (and in
most of the cases, not), that is a totally useless waist of system
resources and energy. The "-nodisp" option is not a solution because it
disables key controls, so we have to kill ffplay with Ctrl-C/Z which is
quite ridiculous and annoying at the same time...

So, my feature request is to make ffplay:
1) accept hotkeys with "-nodisp" option like in showmode, or
2) in showmode can opt for showing only a blank window/custom image, or
3) can play multiple files in the same time, so that we could play an image
and an audio stream together, and use hotkeys for the audio playback.

I know that ffplay is not a fully featured media player, but if it is
capable to display rdft and waves, then it would be not a very hard thing
to implement an option to show only a blank window or nothing...