[linux-audio-user] soundfonts and samplers

Chris Cannam cannam at all-day-breakfast.com
Wed Aug 11 15:48:30 EDT 2004

On Wednesday 11 Aug 2004 8:30 pm, Iván Almada wrote:
> on the other hand ive realized specimen is a great
> sampler:  everything i need (preview .wav, map
> different regions, loop point editor, filter, though
> more different filters would be very very nice...) and
> i didnt know you could use it directly from rosegardan
> through alsa midi ,  that excelent,  just as if
> specimen was a plug in, i can trigger samples from my
> midi keyboard with an inperceptible latency,  now i
> would like to know several more things,  like how to
> apply ladpsa plugins to the sampler for example if i
> want to use some of the ladpsa filters... 

The generic answer to "how do I add effects to this JACK app that 
doesn't immediately appear to support them?" is to use jack-rack, 
which is a very nice standalone JACK effects rack, hosting LADSPA 
plugins.  Run it up and then connect the output of your other JACK 
app (Specimen in this case) into jack-rack using the qjackctl audio 
connection manager.

(I can't remember offhand whether Specimen always outputs to JACK or 
whether it also has direct ALSA output.  You will obviously need to 
have it outputting to JACK and have jackd running [via qjackctl for 
example] to do this.)

> how is the
> audio routed from specimen back into the midi host
> mixer (it displays audio in a channel called rec... )
> but it has no slots for plug ins...

In this case the answer is that the audio is _not_ routed back into 
the midi host.  The only reason you see it on the Rec meter in 
Rosegarden is because Rosegarden's record input is connected to the 
soundcard capture channel, and that is receiving the same audio as is 
being output to the speakers from Specimen.  Even if you could apply 
effects at that point in Rosegarden, it wouldn't alter the sound you 
actually hear while playing.

Note that this also implies that if you record the results straight 
back into Rosegarden as it stands, you'll get some noise because 
you'll be recording the mixed soundcard input, not the pure output 
from Specimen or jack-rack (I think).  For a clean recording, you'd 
have to use the same JACK connection manager to disconnect the 
Rosegarden record input from the ALSA PCM in and reconnect it to the 
output of Specimen or jack-rack or whatever.


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