[linux-audio-user] offline processing

Chris Pickett chris.pickett at mail.mcgill.ca
Tue Feb 17 01:23:24 EST 2004


Erik de Castro Lopo wrote:
> On Mon, 16 Feb 2004 20:28:59 -0500
> Chris Pickett <chris.pickett at mail.mcgill.ca> wrote:
> 
> 
>>Hi,
>>
>>I've been wondering:  what is it like processing audio offline under 
>>Linux?  Is this something that is widely supported?  I did a bunch of 
>>google searches using the term "offline" but couldn't find anything 
>>really useful.
>>
>>My computer is fairly weak (800 MHz laptop, no DSP card).  Currently, if 
>>I want to process a file (apply effects, change the sample rate, apply 
>>dithering, mix it with another file,
> 
> 
> Programs like SoX and sndfile-src (a command line sample rate converter
> which is distributed with libsamplerate) do this.

Thanks for the answer, I've now looked at those.  It seems that SoX is 
limited to the built-in effects and libsamplerate / sndfile-src is just 
for converting sample rates (well, you can tell me otherwise if I'm 
wrong, you're the author Erik :) ...).  It also seems that ecasound can 
do the same, at least for native-to-ecasound things.

What about support for offline LADSPA plugin processing, e.g. 
command-line through ecasound or from within a full-blown GUI thing like 
Rosegarden?

Or, in general, setting up a bunch of applications to produce a final 
output file with JACK, but have it all done offline?

 From what I can tell, things were built to do this from the ground up, 
e.g. in the JACK design document there is a picture of jackd and it says 
"ALSA backend client and clock driver".  But ... it's hard to find 
explicit mention of offline processing because everybody is so worried 
about real-time processing and low latency and all that (understandably 
so), whereas I'm not likely to use this machine for live audio (okay, a 
little bit of real-time-ness is nice in any setup, and I'm sure my 
machine can provide the little I need to edit tracks).

Basically, I would be very happy if somebody could assure me that I 
don't have to worry about running /anything/ real-time in Linux audio if 
I don't want to, save for recording in and playing out through my sound 
card.

Cheers,
Chris


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