Ecasound volume/EQ control

Hi All,

I am using Ecasound on a Raspberry Pi, which functions as a music player in
my car and in a boombox.
It has quite a variety of audio sources, which are all outputting into a
Jack daemon.

I’ve setup Ecasound to receive input from that Jack daemon, add an active
filter, to spit out two mono signals, one for the sub and one for the
woofer, and output to Alsa for playback on the speakers. This is the
command I use:
ecasound --server -z:nodb -z:mixmode,sum -a:pre -f:s32_le,2,44100 -i:jack
-pf:/etc/pre.ecp -o:loop,1 -a:woofer,tweeter -i:loop,1 -a:woofer
-pf:/etc/woofer.ecp -chorder:1,0 -a:tweeter -pf:/etc/tweeter.ecp
-chorder:0,2 -a:woofer,tweeter -f:16,4,44100 -o:alsa

So far, so good.

Unfortunately, my Alsa output, a DAC, doesn’t have a volume control
interface. Could (should?) I (ab)use Ecasound as a volume controller and as
“simple consumer”-style equaliser?
Or is Ecasound not intended for these things? And if so, would I need a
(LADSPA?) plugin for this? If so, suggestions welcome ;-)

(Jack doesn't have volume controls (the available plugins are all GUI, not
suitable for my CLI-based Pi)).

I have Pyecasound running, so ideally I’d control the EQ and Vol using the
ECI commands using Python.

In regards to volume control, I’ve found this message by Luke (
http://nosignal.fi/ecasound-list/2007/09/0004.html). In a reply Kai suggest
using cop-set on the amplification level to control volume. But (and this
illustrates my lack of experience with Eca), cop-set requires a chain-op-id
and param-id, how do I get these for the amplifier operator? Do I have to
actively add this chain-op to my chain setup, or is it always there? Also,
in the above setup the -ea switch couldn't be parsed by ecasound.

Sorry for the “green” question ;-)

Kind regards,
Sjoerd Venema

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