Room correction with convolution per sample rate

[simoncn]

By looking at the verbose output from FFmpeg, I have confirmed that upsampling takes place after filtering.

A simpler alternative to specifying a different convOut string for each sample rate would be to add support for substitution parameters in the convOut string, as follows:

#samplerate# would be replaced with the sample rate of the input file (44, 352, etc.)
#samplebits# would be replaced with the sample bit depth of the input file (16, 24, etc.)

Other values could be added later if required (for example, #outsamplerate# or #outsamplebits#).

With this support, you could use a stream.options setting of

convOut=-i /mnt/disk1/share/MinimServer/convolution/Cor1S#samplerate#.wav -lavfi afir=gtype=gn

to handle files with all sample rates.