Re: [ecasound] loop device trouble

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Subject: Re: [ecasound] loop device trouble
From: Kai Vehmanen (k@eca.cx)
Date: Sun Dec 03 2000 - 19:15:56 EET

On Sat, 2 Dec 2000 ben@slumber.dhs.org wrote:

> ecasound -r -c -b:128 -sr:44100 \
> -a:0 -i:/dev/dsp -eli:1060,0.75,0.50,0.50 \
> -eli:1123,0.00,0.90,0.20,0.30,0.40,1.00 -o:loop,0 \
> -a:1 -i:loop,0 -o:/dev/dsp \
> -a:2 -i:loop,0 -o:out.wav
[...]
> For some reason, there are two lines assigning chain 2's input to loop
> device 0, and nothing for chain 1. If I change one of the lines to

Ok, there's one error in there...:

-a:1,2 -i:loop,0 \
-a:1 -o:/dev/dsp \
-a:2 -o:out.wav

... should work ok. I admit that I made the same error in a loop-related
example I posted to list a few days ago. This inspired me to finally
add a "Tips for writing chainsetups" section to ecasound's user's guide.
Here's the first version:

--cut--
1. Every chain has exactly _one_ input and _one_ output.
2. All inputs and outputs must be connected to some chain.
3. For every input/output, there must be exactly _one_
  input/output specification (example specification: '-i:file.ext').
4. All mixing is based on selecting multiple chains and then
  specifying an input or output (example: '-a:1,2 -i:file.ext').
5. All audio copying and mixing is done channel-wise. If you attach
  a 4-channel input and a two-channel output to a chain, chain
  will have 4 channels of audio, but only the first two channels
  will be written to the output file.
--cut--

So your chainsetup file (as well as my earlier example) broke the third
rule. Although for some tasks, the current syntax feels a bit clumsy,
I feel that it is _very_ important to have a firm logic behind the
chainsetup syntax, without any exceptions. This way if someone
posts a chainsetup file that doesn't work, it's easy to pinpoint the
cause of the problem. We check the rules, and either fix ecasound or
the chainsetup file. 

-- 
 . http://www.eca.cx ... [ audio software for linux ] /\ . 
 . http://www.eca.cx/aivastus ... [ aivastus net radio ] /\ . 

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