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How to Record the Sound Coming From an Application With Pulseaudio

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Say I want to save something that is currently played on my machine.

recording the sound card

Pulseaudio provides a source called monitor for each sound card

pacmd list-sources | grep name: |grep monitor

	name: <alsa_output.usb-GeneralPlus_USB_Audio_Device-00.analog-stereo.monitor>
	name: <alsa_output.usb-C-Media_Electronics_Inc._USB_Audio_Device-00.analog-stereo.monitor>
	name: <alsa_output.pci-0000_00_1f.3.analog-stereo.monitor>

I can see that I have a monitor source for each card I have.

I only need to run parecord then.

parecord --device=alsa_output.usb-GeneralPlus_USB_Audio_Device-00.analog-stereo.monitor > output.wav

recording from an application only

Following this instructions1

pacmd list-sink-inputs

2 sink input(s) available.
    index: 131
        driver: <protocol-native.c>
        flags:
        state: RUNNING
        sink: 0 <alsa_output.usb-GeneralPlus_USB_Audio_Device-00.analog-stereo>
        volume: front-left: 65536 / 100% / 0.00 dB,   front-right: 65536 / 100% / 0.00 dB
                balance 0.00
        muted: no
        current latency: 287.33 ms
        requested latency: 42.67 ms
        sample spec: s16le 2ch 48000Hz
        channel map: front-left,front-right
                     Stereo
        resample method: (null)
        module: 9
        client: 147 <ALSA plug-in [sox]>
        properties:
                media.name = "ALSA Playback"
                application.name = "ALSA plug-in [sox]"
                native-protocol.peer = "UNIX socket client"
                native-protocol.version = "35"
                application.process.id = "2753496"
                application.process.user = "sam"
                application.process.host = "konixwork"
                application.process.binary = "sox"
                application.language = "C"
                window.x11.display = ":0"
                application.process.machine_id = "21fdcf6901834b06813ffa8423c27210"
                application.process.session_id = "2"
                module-stream-restore.id = "sink-input-by-application-name:ALSA plug-in [sox]"
    index: 144
        driver: <protocol-native.c>
        flags:
        state: RUNNING
        sink: 0 <alsa_output.usb-GeneralPlus_USB_Audio_Device-00.analog-stereo>
        volume: front-left: 65536 / 100% / 0.00 dB,   front-right: 65536 / 100% / 0.00 dB
                balance 0.00
        muted: no
        current latency: 107.98 ms
        requested latency: 30.00 ms
        sample spec: s16le 2ch 48000Hz
        channel map: front-left,front-right
                     Stereo
        resample method: (null)
        module: 19
        client: 189 <ALSA plug-in [snapclient]>
        properties:
                media.name = "ALSA Playback"
                application.name = "ALSA plug-in [snapclient]"
                native-protocol.peer = "UNIX socket client"
                native-protocol.version = "33"
                application.process.id = "1"
                application.process.user = "sam"
                application.process.host = "konixwork"
                application.process.binary = "snapclient"
                application.language = "C"
                application.process.machine_id = "79372d8564c8545262975c46157f1482"
                module-stream-restore.id = "sink-input-by-application-name:ALSA plug-in [snapclient]"

My snapclient is running on sink 144.

I then run

pactl load-module module-null-sink sink_name=steam
pactl move-sink-input 144 steam

And get the sound to stop being heard.

Then

parecord -d steam.monitor > truc.wav

And then vlc truc.wav shows that the file indeed contains the sound.

I don’t know the difference between parecord and parec, but the suggested command works as well.

parec -d steam.monitor | oggenc -b 192 -o steam.ogg --raw -

record only one application while still hearing the sound

I want the sink input to go to the null sink and be recorded to a file while still be streamed.

I can combine two sinks into one with the module-combine-sink.

Provided I already created the null sink.

pactl load-module module-combine-sink sink_name=combined slaves=steam,alsa_output.usb-GeneralPlus_USB_Audio_Device-00.analog-stereo

Then I can move the application to use the combined sink.

pactl move-sink-input 144 combined

The sound will go to the sound card AND to the null sink, allowing me to hear the sound while recording it with.

parecord -d steam.monitor > truc.wav

doing the same thing without the extra null sink

Actually, what I need is only a proxy sink that will redirect its content to the sound card and record this proxy. This can simply achieved with the same module.

pactl load-module module-combine-sink sink_name=proxy slaves=alsa_output.usb-GeneralPlus_USB_Audio_Device-00.analog-stereo
parecord -d proxy.monitor > output.wav

  1. Try something like this:

    In a terminal enter

    pacmd (this is the CLI of the PulseAudio-Server) then use

    list-sink-inputs (where you get the indices of the running inputs) Now find the index of your input. Now referred to as $INDEX

    the scriptable part is:

    1. pactl load-module module-null-sink sink_name=steam
    2. pactl move-sink-input $INDEX steam
    3. parec -d steam.monitor | oggenc -b 192 -o steam.ogg –raw -

    Explanations:

    1. The first command will add a null-sink as you already knew.
    2. The second command moves the sink-input from your standard-audio-sink to steam
    3. The third command records the monitor of the device steam (-d) and puts the output (raw-wave-stream) into oggenc, which encodes this wave-stream to an oga-file. (for mp3 use lame)

    — https://askubuntu.com/questions/60837/record-a-programs-output-with-pulseaudio

     ↩︎