[SoX-users] Filter only one channel

[windy <oon...@gm...>]

I have a program that needs to continuously compare a signal sinc-filtered
by sox to the original, non-filtered one. The signal is captured from a
device in real time, and nothing is saved on disk.

Obviously, the program cannot get its comparison (non-filtered) signal from
the same device sox is recording, so it seems I need to convert the signal
to stereo in sox, filter only one channel and then output both channels for
comparison. Is this possible in sox? Or is there an obvious piping hack I'm
missing?

Oona