Subject: Re: [ecasound] tracking with ecasound 1.6.12
From: Kai Vehmanen (kaiv@wakkanet.fi)
Date: Thu Feb 24 2000 - 14:35:53 EET
On Thu, 24 Feb 2000, Neil E. Klepeis wrote:
> 1. Is it possible from within ecasound to direct the left channel from
> a sound card device to one file, and the right channel to another
> file? Thereby resulting in two mono sound files. I suppose this is
Yep,
ecasound -f:16,2,44100 -a:1,2 -i /dev/dsp \
-a:1 -f:16,1,44100 -o mono-1.wav \
-a:2 -f:16,1,44100 -o mono-2.wav -erc:2,1
The idea is to attach the stereo input to two chains. When ecasound
copies data input->chain and chain->output, channels are never
mixed. So channel0 is copied to channel0, c1 to c1, etc... Because
of this, we add -erc:2,1 to the second chain. This copies all
data from channel 2 to channel 1.
> 2. I am having a lot of trouble getting clean tracks when multitracking
> (e.g., playing 2 or three sound files, and recording another from a
> sound card). There appear a lot of clicks and pops during the tracks
> even though the first 20-30 seconds may sound perfect. Sometimes I
Hmm, what kernel are you using, have you enable DMA-mode for your
harddisks, what sound card drivers (OSS/ALSA, what card)?
> don't hear any problems during the actually tracking (recording) and the
> problem only comes up when I play all the tracks back. I am setting a
> buffer of 64 (-b:64) during recording and 1024 during playback. There
> don't appear to be any timing problems. My question is: does this
-b:64 is quite small. It works fine on some hardware, but not all.
I often use -b:128 myself. Btw; if you play the recorded tracks
independently, do you here the clicks?
> sound like a buffer issue or is there some other problem (e.g., not
> enough CPU power available)? My machine is a PII/350MHz/128MB with RH
> Linux 6.1. Does encoding mp3's on the fly with lame (or decodeing with
> mpg123) use up more of the CPU than just using wav files?
Definitely. mp3 encoding and decoding are very cpu-intensive tasks.
You can use 'top' to see how much lame/mpg123 are using cpu-power while
you use ecasound.
> 3. I am very interested in being able to loop one chain (e.g., playback
> 4 sec of a sound file over and over) while other chains keep playing
> straight through. eg, have a two bar drum loop and record guitar or
> vocals over it. I don't think this is now possible with the -t and -tl
> options or loop devices. Are there plans for such a feature?
It's already available on 1.7.x versions. You create an ascii file with
extension .ewf ...
--- track.ewf --
source = some_track.wav
offset = 20.000000
length = 25.000000
looping = true
start-position = 9.500000
--cut--
Then you can use it like any other input: "ecasound -i track.ewf -o
/dev/dsp". With the above configuration, ecasound will start using
'some_track.wav' when position 20sec is reached. Then ecasound
seeks to position 9.5sec (inside some_track.wav) and starts reading
audio data. After 25secs it'll loop back to 9.5sec inside the audio
file.
-- Kai Vehmanen <kaiv@wakkanet.fi> -------- CS, University of Turku, Finland . http://www.wakkanet.fi/ecasound/ - linux multitrack audio processing . http://www.wakkanet.fi/sculpscape/ - ambient-idm-rock-... mp3/ra/wav
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