Is there a quick, not much processing time needed, way to make the same
volume on a 16 signed int stream in real time?

I've heard of replaygain, rms, and fft now, but I don't think I have the
processing time able to devote to doing a perfect job of making multiple
streams the same volume in decibels. Is there a quick way / algorithm I can
look at the stream of 16 bit integers that will do a sufficient job? I
don't think I have the processing time available to consider all the
frequencies, how loud they are perceived, the energy, and averaging the DC
component.

Thanks,

SA Dev