From 3b4da925730c62e7533e692ec004fbdee6665ecc Mon Sep 17 00:00:00 2001
From: dvs1
Date: Fri, 25 Oct 2024 13:47:07 +1000
Subject: Should add this test asoundrc, though it's not working yet.

---
 spread.asoundrc | 88 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 88 insertions(+)
 create mode 100644 spread.asoundrc

diff --git a/spread.asoundrc b/spread.asoundrc
new file mode 100644
index 0000000..15d77a8
--- /dev/null
+++ b/spread.asoundrc
@@ -0,0 +1,88 @@
+# From https://wiki.archlinux.org/title/Advanced_Linux_Sound_Architecture/Configuration_examples#Loopback_interface_with_dmix_external_interface
+
+# Use this to output to external
+pcm.dmixerout {
+ type dmix
+ ipc_key 1024
+ ipc_key_add_uid false
+ slave {
+  pcm "hw:CARDNAME,0"
+  channels 2
+  period_time 0
+  period_size 1024
+  buffer_size 4096
+  rate 44100
+ }
+ bindings {
+  0 0
+  1 1
+ }
+}
+
+# Use this to output to loopback
+pcm.dmixerloop {
+ type dmix
+ ipc_key 2048
+ ipc_key_add_uid false
+ slave {
+  pcm "hw:Loopback,0,0"
+  channels 2
+  period_time 0
+  period_size 1024
+  buffer_size 4096
+  # If format is absent ALSA gives me slave PCM not usable, but it works w/o it for others
+  format S32_LE
+  rate 44100
+ }
+ bindings {
+  0 0
+  1 1
+ }
+}
+
+# Sends to the two dmix interfaces
+pcm.quad {
+ type multi
+ # Necessary to have both slaves be dmix; both as hw doesn't give errors, but wouldn't 
+ slaves.a.pcm "dmixerout"
+ slaves.a.channels 2
+ slaves.b.pcm "dmixerloop"
+ slaves.b.channels 2
+ bindings {
+  0 { slave a; channel 0; }
+  1 { slave a; channel 1; }
+  2 { slave b; channel 0; }
+  3 { slave b; channel 1; }
+ }
+}
+
+# Duplicates to quad, use this to output to loopback & external
+pcm.stereo2quad {
+ type route
+ slave.pcm "quad"
+ # ttable.A.B G
+ # where A - input channel
+ #       B - output channel
+ #       G - volume gain (1.0 = original)
+ ttable.0.0 1
+ ttable.1.1 1
+ ttable.0.2 1
+ ttable.1.3 1
+}
+
+# Listens to loopback
+# trying to play to stereo2quad when something is already listening gives me slave PCM not usable
+# but listening when something is already playing on stereo2quad works
+# and so does starting to listen, then playing to dmixerloop
+pcm.loopin {
+ type dsnoop
+ ipc_key 1111
+ ipc_key_add_uid false
+ slave.pcm "hw:Loopback,1"
+}
+
+pcm.!default {
+ type asym
+ playback.pcm "plug:stereo2quad"
+ capture.pcm "plug:loopin"
+}
-- 
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