Added notes for increasing number of audio vchannels under FreeBSD.

diff --git a/data/notes/freebsd_11.md b/data/notes/freebsd_11.md
index 009e557..d7b49c1 100644 (file)
--- a/data/notes/freebsd_11.md
+++ b/data/notes/freebsd_11.md
@@ -238,7 +238,7 @@ In `about:config`:
 
 Note that the `gfx.*` entries enable hardware acceleration since the Nvidia
 drivers I am using support cairo but not skia, or is it that cairo supports my
 
 Note that the `gfx.*` entries enable hardware acceleration since the Nvidia
 drivers I am using support cairo but not skia, or is it that cairo supports my

-video drives and skia doesn't?
+video drivers and skia doesn't?

 
 In preferences:
 
 
 In preferences:
 


@@ -276,6 +276,72 @@ create the file `~/.config/gtk-3.0/settings.ini` with contents:
     gtk-primary-button-warps-slider=false
 
 
     gtk-primary-button-warps-slider=false
 
 

+# Audio Configuration #
+
+By default, FreeBSD only provides 16 virtual audio channels via `/dev/dsp`.
+Since Firefox appears to open a new connection for each tab that plays audio
+and does not release those connections as long as the tab remains open, I
+sometimes encounter error messages like the following.
+
+    mpv: can't open /dev/dsp!
+
+To verify the problem, use `fstat` to confirm that too many connections exist.
+
+    ataylor@lagavulin:~ % fstat | grep dsp
+    ataylor  mpv        42458   27 /dev        215 crw-rw-rw-  dsp0.15  w
+    ataylor  mpv        36531   27 /dev        194 crw-rw-rw-  dsp0.11  w
+    ataylor  mpv        24332   25 /dev        204 crw-rw-rw-  dsp0.13  w
+    ataylor  firefox    61929   48 /dev        209 crw-rw-rw-  dsp0.14  w
+    ataylor  firefox    61718   23 /dev        259 crw-rw-rw-  dsp0.22  w
+    ataylor  firefox    61718   47 /dev        296 crw-rw-rw-  dsp0.46  w
+    ataylor  firefox    61718   51 /dev        273 crw-rw-rw-  dsp0.30  w
+    ataylor  firefox    61718   64 /dev        284 crw-rw-rw-  dsp0.40  w
+    ataylor  firefox    61718   68 /dev        245 crw-rw-rw-  dsp0.17  w
+    ataylor  firefox    61718   70 /dev        265 crw-rw-rw-  dsp0.25  w
+    ataylor  firefox    61718   73 /dev        280 crw-rw-rw-  dsp0.36  w
+    ataylor  firefox    61718   74 /dev        188 crw-rw-rw-  dsp0.10  w
+    ataylor  firefox    61718   75 /dev        278 crw-rw-rw-  dsp0.34  w
+    ataylor  firefox    61718   76 /dev        272 crw-rw-rw-  dsp0.29  w
+    ataylor  firefox    61718   79 /dev        282 crw-rw-rw-  dsp0.38  w
+    ataylor  firefox    61718   80 /dev        293 crw-rw-rw-  dsp0.43  w
+    ataylor  firefox    61695   47 /dev        264 crw-rw-rw-  dsp0.24  w
+    ataylor  firefox    61695   48 /dev        279 crw-rw-rw-  dsp0.35  w
+    ataylor  firefox    61695   66 /dev        274 crw-rw-rw-  dsp0.31  w
+    ataylor  firefox    61695   69 /dev        292 crw-rw-rw-  dsp0.42  w
+    ataylor  firefox    61620   17 /dev        247 crw-rw-rw-  dsp0.18  w
+    ataylor  firefox    61620   72 /dev        291 crw-rw-rw-  dsp0.41  w
+    ataylor  firefox    61208   17 /dev        254 crw-rw-rw-  dsp0.20  w
+    ataylor  firefox    61208   18 /dev        275 crw-rw-rw-  dsp0.32  w
+    ataylor  firefox    61208   48 /dev        201 crw-rw-rw-  dsp0.12  w
+    ataylor  firefox    59654   45 /dev        276 crw-rw-rw-  dsp0.33  w
+    ataylor  firefox    59654   70 /dev        295 crw-rw-rw-  dsp0.45  w
+    ataylor  python2.7  82359   20 /dev        145 crw-rw-rw-  dsp0.16  w
+
+Before proceeding, ensure that no processes have `/dev/dsp` open. IOW, the
+above `fstat` list should be empty.
+
+With nothing using the audio device, increase the number of virtual channels
+with `sysctl`.
+
+    root@lagavulin:~ % sysctl -a | grep vchans
+    hw.snd.maxautovchans: 16
+    dev.pcm.2.play.vchans: 1
+    dev.pcm.1.play.vchans: 1
+    dev.pcm.0.rec.vchans: 4
+    dev.pcm.0.play.vchans: 16
+    
+    root@lagavulin:~ # sysctl dev.pcm.0.play.vchans=256
+    dev.pcm.0.play.vchans: 16 -> 256
+    
+    root@lagavulin:~ # sysctl hw.snd.maxautovchans=256
+    hw.snd.maxautovchans: 16 -> 256
+
+Add the following two lines to `/etc/sysctl.conf` so the change persists.
+
+    dev.pcm.0.play.vchans=256
+    hw.snd.maxautovchans=256
+
+

 # X11 Configuration #
 
 In `~/.Xresources`:
 # X11 Configuration #
 
 In `~/.Xresources`: