[ecasound] Ecasound newbie - convert 4 channel to twin stereo

So I had never used Ecasound before until yesterday, but I found a
project on GitHub <https://github.com/markmerz/ladspa-sq-sv> where
someone had written a SQ Quadraphonic decoder as a LADSPA plugin, and so
I installed the plugin and ecasound, and tried to make it work in the
way that I needed.

The example command on the plugin page was:

    ecasound -x -i sq-test-tones.m4a -el:hilbert_stereo_200taps
    -el:sq_decoder_shadow_vector -f:,4 -o test.wav

This takes a two-channel input file with some SQ quadraphonic test tones
and produces a single 4-channel discrete quadraphonic file. However, my
goal is to have ecasound take a realtime input from an ALSA device,
decode the SQ signal using the plugin, then output to two 2-chanel
devices, one for the front set of speakers, and one for the rear set of
speakers. I currently don't have the ALSA devices setup with the system
I will be using (an original Raspberry Pi Model B), so I'm using files
as placeholders for the input and output devices.

I tried the following command, based upon the original command from the
plugin page and the ecasound documentation for multitrack usage:

    ecasound -a:1,2 -x -i sq-test-tones.m4a -el:hilbert_stereo_200taps
    -el:sq_decoder_shadow_vector -a:1 -f:16,2,44100 -o front.wav -a:2
    -f:16,2,44100 -o back.wav -chcopy:3,1 -chcopy:4,2

unfortunately, this gives the error "Exactly one chain should be
selected when adding chain operators". I can get this to work
individually, by using this command to get the front set of speakers:

    ecasound -x -i sq-test-tones.m4a -el:hilbert_stereo_200taps
    -el:sq_decoder_shadow_vector -f:,4 -a:1 -f:16,2,44100 -o front.wav

and this one for the rear set of speakers:

    ecasound -x -i sq-test-tones.m4a -el:hilbert_stereo_200taps
    -el:sq_decoder_shadow_vector -f:,4 -a:1 -f:16,2,44100 -chcopy:3,1
    -chcopy:4,2 -o back.wav

but I really need to to be all in one command.

Would someone with more experience with ecasound be able to guide me
towards a solution to this?

Thanks,

Andrew

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Received on Sun Jun 16 21:14:39 2019