Re: [ecasound] chain setup equivalence

Hi,

On Sun, 6 Dec 2009, Joel Roth wrote:

>> I wonder if these two lines are equivalent:
>>
>> -a:1,2 -i:something
>>
>> -a:1 -i:something -a:2 -i:something

you replied to yourself already, but just you confirm that no, those are
not equivalent. Every '-i' and '-o' is a separate "add input/output"
actions. So the former adds one input to two chains, while the latter adds
two separate inputs (that both happen to be labelled 'something') to two
chains.

> Attempting to answer my own question, the following
> is valid:
>
> -a:1 -i:foo.wav
> -a:2 -i:bar.wav
> -a:1 -o:null
> -a:2 -o:null

Yes, this is valid, but note that two independent instance of 'null' are
created. "-a:1,2 -o:null" is different in that only one 'null' object is
created.

> But not this:
>
> -a:1 -i:foo.wav
> -a:2 -i:bar.wav
> -a:1 -o:loop,1
> -a:2 -o:loop,1

This fails as 'loop' object raise an error if one tries to create multiple
loops objects with the same id (same same direction).

> You would need to say:
>
> -a:1 -i:foo.wav
> -a:2 -i:bar.wav
> -a:1,2 -o:loop,1

Or:
  -a:1 -i:foo.wav
  -a:2 -i:bar.wav
  -a:1 -o:loop,1
  -a:2 -o:loop,2

Now create two 'loop' objects is ok as they have unique id's. But of
course, usually you specifically want to attach the chains to the same
loop object instance (and thus "-a:1,2 -o:loop,1" is what you want).

...

The reason why this works like this is to make it easy to specify all
routing (also the complex types) on the command-line. Well, not 100% sure
about "easy", but at least with less typing. ;) One important bit is the
this syntax for linking an input/output to multiple chains, while still
allowing to have multiple instance of similar objects (e.g. multiple
independent inputs reading from the same file).

The approach is on purpose different than in gstreamer (how one connects
pads of gstreamer pipelines when using gst-launch) and JACK port
connections.

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Received on Mon Jan 18 00:15:01 2010