Changes between Version 5 and Version 6 of Capture/ALSA

Timestamp:

Nov 12, 2014, 8:13:23 PM (12 years ago)

Author:

c-14

Comment:

Add recording audio from application examples.

Capture/ALSA

@@ -132 +132 @@
 = Examples =
 
-== Grab an audio from your microphone ==
+== Record audio from your microphone ==
 
 When doing screencast recordings, you usually want to record your voice too:
@@ -142 +142 @@
 ffmpeg -f alsa -ac 1 -ar 44100 -i default:CARD=ICH5 -t 30 out.wav
 }}}
+
+== Record audio from an application ==
+Load the snd_aloop module:
+{{{
+modprobe snd-aloop pcm_substreams=1
+}}}
+Set the default ALSA audio output to one substream of the Loopback device in your .asoundrc (or /etc/asound.conf)
+{{{
+# .asoundrc
+pcm.!default { type plug slave.pcm "hw:Loopback,0,0" }
+}}}
+You can now record audio from a running application using:
+{{{
+ffmpeg -f alsa -ac 2 -ar 44100 -i hw:Loopback,1,0 out.wav
+}}}
+
+== Record audio from an application while also routing the audio to an output device ==
+Load the snd_aloop module:
+{{{
+modprobe snd-aloop pcm_substreams=1
+}}}
+Set up your .asoundrc (or /etc/asound.conf) like so:
+{{{
+# .asoundrc
+pcm.multi {
+    type route;
+    slave.pcm {
+        type multi;
+        slaves.a.pcm "output";
+        slaves.b.pcm "loopin";
+        slaves.a.channels 2;
+        slaves.b.channels 2;
+        bindings.0.slave a;
+        bindings.0.channel 0;
+        bindings.1.slave a;
+        bindings.1.channel 1;
+        bindings.2.slave b;
+        bindings.2.channel 0;
+        bindings.3.slave b;
+        bindings.3.channel 1;
+    }
+
+    ttable.0.0 1;
+    ttable.1.1 1;
+    ttable.0.2 1;
+    ttable.1.3 1;
+}
+
+pcm.!default {
+        type plug
+        slave.pcm "multi"
+} 
+
+pcm.output {
+        type hw
+        card Headset
+}
+
+pcm.loopin {
+        type plug
+        slave.pcm "hw:Loopback,0,0"
+}
+
+pcm.loopout {
+        type plug
+        slave.pcm "hw:Loopback,1,0"
+}
+}}}
+where the output pcm points to the output device you want the audio to go to.
+
+You can now record audio from a running application using:
+{{{
+ffmpeg -f alsa -ac 2 -ar 44100 -i loopout out.wav
+}}}