[ecasound] JACK plugin added to ecasound

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Subject: [ecasound] JACK plugin added to ecasound
From: Kai Vehmanen (k_AT_eca.cx)
Date: Sun Dec 16 2001 - 03:44:36 EET

Committed to CVS. Experimental but works. 

---
Setup:

To use it, update ecasound tree from CVS, and give --with-jack=/path/to
option to configure. I've installed jack in ~/apps/jack so I use
--with-jack=/home/user/apps/jack; with default jack install you'd use
--with-jack=/usr/local.

---
And actual use:

	./jackd -p 128 -r 44100 &
 	ecasound -b:128 -i foo.wav -o jack,ecaoutput1
	ecasound -b:128 -i jack,ecarec -o foo.wav

---
Known limitations:

- you must manually set buffersize to match jackd's buffersize;
  ie. 'jackd -p x ...' --> 'ecasound -b:x ...'
- you must manually set sample rate
  ie. 'jackd -r 48000 ...' --> 'ecasound -sr:48000 ...'
- don't use multiple JACK plugins in the same chainsetup (hangs
  in UNIX-socket poll() somewhere in JACK client code)
- only mono output and input supported; depending on direction,
  ecasound makes a connection to either 'ALSA I/O:Input 1' or
  'ALSA I/O:Output 1'

---
Performance 

Playback and recording works without xruns even with '-p 64', but is very
sensitive to outside events. I'm not running a ll-patched kernel so this
is to be expected. Also, the ecasound JACK plugin has lots of room for
optimization. As it is now, two pthread_cond+pthread_signal combinations
are issued per period.

There are lots of misc problems. When something goes wrong you usually
have to "killall -9 jackd ; rm -f /tmp/jack* ; ./jackd".

---
Patches&stuff

I'm using ALSA0.9 ens1371 driver. With the current JACK CVS-tree I
couldn't run jackd with '-r 44100'. ens1371 (unlike ens1370) has a
continuous range of supported sample rates. This also means that if you
request for 44100 you don't get that exact rate. Or at least this is my
interpretation. In any case I get an error from
'snd_pcm_hw_param_set_rate()'. I got around this with the following
change:

--cut--
diff -u -r1.9 alsa_driver.c
--- alsa_driver.c	2001/12/08 18:11:38	1.9
+++ alsa_driver.c	2001/12/16 01:18:09
@@ -219,7 +219,7 @@
 		}
 	}
 
-	if ((err = snd_pcm_hw_params_set_rate (handle, hw_params, driver->frame_rate, 0)) < 0) {
+	if ((err = snd_pcm_hw_params_set_rate_near (handle, hw_params, driver->frame_rate, 0)) < 0) {
--cut--

And another very, very important patch :)...

--cut--
--- AUTHORS	2001/11/12 04:08:38	1.1.1.1
+++ AUTHORS	2001/12/16 01:18:09
@@ -5,7 +5,7 @@
     Paul Davis
     David Olofson
     Benno Sennoner
-    Kai Vehamen
+    Kai Vehmanen
--cut--

-- 
 http://www.eca.cx
 Audio software for Linux!

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