Re: channel manipulation

On Sat, Sep 29, 2012 at 06:54:11PM +1000, Patrick Shirkey wrote:
 
> On Sat, September 29, 2012 6:14 pm, Joel Roth wrote:
> > Hi Patrick,
> >
> > You mention the learning curve of Ecasound. I think it
> > reflects the curve of learning to think in
> > terms of audio streams and operators for manipulating
> > them. Similar difficulties dog those who would exercise
> > the full capabilities of ALSA using .alsarc files.
> >
> 
> It's more about the syntax. Being text based it is easy to make mistakes
> in the signal flow but I am getting my head around it now. It's an elegant
> way of getting things done once you know what you are doing.
 
Yes, elegant and yes, with syntactical requirements like
any programming language.
 
> The input file is a stereo track. The output file is a 6 channel track.

Oops. 
 
> >> converter script:
> >>
> >> ecasound -t 5 -f:s16_be,6,48000 \
> >> -a:1,2,3,4,5,6 -i TEST_1-2.aif \ # each chain 1-6 gets a copy of six
> >> channel audio
> >> -a:1 -chmute:2 \ # chain 1, channel 2 is muted, other 5 channels alive
> >> -a:2 -chmute:1 \ # chain 2, channel 1 is muted, other 5 channels alive
> >> -a:3 -chmix:3  \ # chain 3, all six channels mixed to channel 3
> >> -a:4 -chmix:4  \ # chain 4, all six channels mixed to channel 4
> >> -a:5 -chmute:1  \# chain 5, channel 1 is muted, other 5 channels alive
> >> -a:6 -chmute:2 \ # chain 6, channel 2 is muted, other 5 channels alive
> >> -a:5,6 -o loop,1 \ # chains 5 and 6 summed to loop device loop,1
> >> -a:7,8 -i loop,1 \ # chains 7 and 8 each get copy of loop,1 stream
> >> -a:7  -ea:200 -chmix:5 \ # chain 7, all channels amplified, then
> >                            # summed in channel 5
> >> -a:8  -chmix:6 \         # chain 8, all channels summed in channel 6
> >> -a:all -o test-out.wav   # all channels in all chains summed to
> >> test-out.wav
> >
> >
> > I think this may not be what you want to accomplish, because
> > you're summing lots of copies of the same channels.
> >
> 
> The input track is a stereo track so I am only summing copies of the left
> and right signal input signal.  The output track is a 6 channel track. I
> have removed all the additional processing filters to minimise confusion
> ;-)

Okay, well the comments above still apply, even if the input
is just two channels. :-)

 
> >> +++
> >>
> >> ecasound: ERROR: [ECA-SESSION] : "Invalid argument, unable to parse:
> >> "-chmix:5""
> >>
> >> ecasound -t 5 -f:s16_be,6,48000 \
> >> -a:1,2,3,4,5,6 -i TEST_1-2.aif \
> >> -a:1 -chmute:2 \
> >> -a:2 -chmute:1 \
> >> -a:3 -chmix:3  \
> >> -a:4 -chmix:4  \
> >> -a:5 -chmute:1  \
> >> -a:6 -chmute:2 \
> >> -a:5,6 -chmix:5 -chcopy:5,6 \
> >> -a:all -o test-out.wav
> >>
> >> +++
> >
> > Not sure what differently you want to accomplish
> > with this second command.
> 
> With the first command I get silence on channels 5,6 output. With the
> second command I am trying to chmix a:5,6 to channel 5 to see if that
> gives me an audible signal on the output track. However it fails for some
> reason. It doesn't want to chmix chain 5 and 6 at the same time. It is
> happy to do them individually for chain 3 and 4. I'm not sure why that
> would be a problem though.

I would try creating your setup in small pieces and testing
each piece. If you can get a good result processing
chains separately, I would go for that.

You may also find it easier (as I do) to write your commands to a file
(e.g. Setup.ecs) and load it with

ecasound -c -s Setup.ecs

That way it's more like writing and testing any other program.

Have fun (and working chain setups)

Joel


> 
> --
> Patrick Shirkey
> Boost Hardware Ltd
> 
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-- 
Joel Roth

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