See also a1ba561cc5. JACK2 and pipewire unconditionally
report 32kB, Ardour internal backends report 8kB, also
independent of the buffersize.
While jack1 by default announces the audio buffersize.
A sensible value assumes that the GUI reads the FIFO at
a least 25fps, while also allowing MIDI ports to merge
data (hence 2 * raw_buffer_size). Yet limit to 64k per track.
eac3283b49