Record audio from command line

[fozner]

My needs are simple. I would like to record audio from the command line. The problem: I use Fedora 8, with pulseaudio enabled by default. None of the populare alsa/oss recording tools work. So far, I have tried:

arecord -Dpulse -t wav this.wav
streamer -t 0:30 -O soundtrack.wav -F stereo
oss: open /dev/dsp: Device or resource busy
padsp streamer -t 0:30 -O soundtrack.wav -F stereo
oss: open /dev/dsp: Device or resource busy
ffmpeg -f audio_device -i /dev/dsp -f x11grab -s vga -i :0.0+10,20 out.mpg
/dev/dsp: Device or resource busy
padsp ffmpeg -f audio_device -i /dev/dsp -f x11grab -s vga -i :0.0+10,20 out.mpg
(resultant file is corrupt)
ecasound -i alsahw,0,1 -o test.wav
(records blank test.wav)
padsp ecasound -i /dev/dsp -o test.wav
(blocks/hangs)

Audacity works, but alas, audacity is not a command-line tool.

[Dangermouse]

Have you tried
arecord -f cd -t raw | lame -x - out.mp3

[Dangermouse]

Sorry of course you need lame installed as well

yum install lame

[fozner]

Thanks, I'll try that. I also did not think to try disabling pulseaudio with (I think*) pulseaudio -k and then re-enabling it with pulseaudio -D after I'm done playing around. When things aren't so busy around here I"ll give it a shot.

Edit: Nope! Didn't work. Also tried disabling pulseaudio but it makes things worse. So does removing alsa-plugins-pulseaudio-1.0.14-5.fc8.x86_64.rpm. It appears that recording audio from the command line is impossible without completely removing all pulseaudio packages --nodeps which is, shall we say, inconvenient.

Why this functionality is wanted: Originally, I was going to do some desktop session recording with ffmpeg -X11grab (X11grab is unavailable in the rpm version of ffmpeg. I had to compile it special for that.) Anyway, it would be convenient if I could record audio and video together instead of recording them separately and then merging them together with avidemux, paying particular attention to syncing them correctly. Perhaps I am asking too much and should go back to playing super tux cart.

[fozner]

Through trial and error, I was eventually able to record form the mic using the following command. Interestingly, it only works 50% of the time. The other 50% of the time results in a blank (no noise) audio file of the same length.

arecord -v -Dplughw:0,2 -N -d 10 -r48k -c2 this.wav

Later on, I learned that I could enumerate the available capture devices with aplay -l

aplay-l | grep card
card 0: Live [SBLive! Value [CT4871]], device 0: emu10k1 [ADC Capture/Standard PCM Playback]
card 0: Live [SBLive! Value [CT4871]], device 2: emu10k1 efx [Multichannel Capture/PT Playback]
card 0: Live [SBLive! Value [CT4871]], device 3: emu10k1 [Multichannel Playback]

You can see how card 0: device 2 translates into hw:0,2 but pulseaudio is using hw:0,2 so it appears busy. That's why I had to use plughw:0,2
And to make it the default recording device, I modified .asoundrc in my home directory:

pcm.pulse {
	type pulse
 }
pcm.!default {
 type asym
	playback.pcm "pulse"
	capture.pcm "plughw:0,2"
 }
 ctl.!default {
	type pulse
 }

Now simple commands like "arecord -d 5 this.wav" work as expected but... is it a hack?

[kadambi]

Not sure if this'd help but give this a try:

Have you set sound capture preferences to ALSA?

System ->Preferences->Hardware->Sound

[fozner]

Yes but those settings seem to be for gnome apps. They don't seem to affect command line tools like arecord or other window managers like xfce, kde...

Hmm, my hack bypasses pulseaudio completely for recording purposes, which is ok for me I guess, since I'm not using thin clients or anything network audio. It would be better if I knew enough to tell pulseaudio what to do.

Edit: I'm starting to get a clue. I'm seeing stuff in the logs when pulseaudio starts up. Yup, this is why I couldn't record: I think I can figure it out now. :O

Nov 20 18:48:45 arrgh pulseaudio[4243]: module-alsa-source.c: Error opening PCM device hw:0: Device or resource busy
Nov 20 18:48:45 arrgh pulseaudio[4243]: module.c: Failed to load module "module-alsa-source" (argument: "device=hw:0 source_name=alsa_input.pci_1102_2_alsa_capture_0") : initialization failed.

It is because hotplug trying to load the same device twice. http://www.pulseaudio.org/ticket/128

[fozner]

My latest hack involves looking at the output of aplay -l and adding the card (0 in my case) and input device (2 in my case) right after plughw in the following line in /etc/pulse/default.pa.

add-autoload-source input module-alsa-source device=plughw:0,2 source_name=input

And then I run padevchooser tray icon, change default source to "input". My mic now works and is more or less correctly controlled by pulseaudio, but there are still errors in the log???

W: alsa-util.c: Device plughw:0,2 doesn't support 44100 Hz, changed to 48000 Hz.
ALSA lib control.c:909snd_ctl_open_noupdate) Invalid CTL plughw:0,2
W: alsa-util.c: Unable to attach to mixer plughw:0,2: No such file or directory