Chromium --alsa-ouput-device flag not working

user_3170450 0
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I have created a virtual alsa loopback device and trying to open a youtube link in google-chrome or chromium-browser and trying to send it's audio output to that virtual device. Then using ffmpeg I am trying to capture the audio. But no matter what I do, chrome or chromium always send audio output to default built-in speakers. If I open volume control panel and change the output of the application in playback section to loopback then it works. But my requirement to be able to do it programatically by telling the chrome to send audio on which device.

Following are the commands which I tried to make it happen:

google-chrome --window-position=0,0 --window-size=1920,1080 --alsa-output-device=alsa_output.1.analog-stereo.monitor -kiosk https://www.youtube.com/watch?v=LTbnmiXWs2k

google-chrome --window-position=0,0 --window-size=1920,1080 --alsa-output-device=hw:1,0 -kiosk https://www.youtube.com/watch?v=LTbnmiXWs2k

And following is the ffmpeg command which is working fine:

ffmpeg -f pulse -i alsa_output.1.analog-stereo.monitor -ac 1 -ar 16000 test.wav

Any help will be appreciated.

alsa google-chrome chromium
2 Answers

I have also suffered from the same problem, as Google didn't provide the complete format for ALSA output usage, so you can follow below procedure,

  1. list out the plug hardware:

    aplay -L

null
    Discard all samples (playback) or generate zero samples (capture)
pulse
    PulseAudio Sound Server
default:CARD=PCH
    HDA Intel PCH, ALC662 rev3 Analog
    Default Audio Device
sysdefault:CARD=PCH
    HDA Intel PCH, ALC662 rev3 Analog
    Default Audio Device
front:CARD=PCH,DEV=0
    HDA Intel PCH, ALC662 rev3 Analog
    Front speakers
surround21:CARD=PCH,DEV=0
    HDA Intel PCH, ALC662 rev3 Analog
    2.1 Surround output to Front and Subwoofer speakers

  2. Now select your plug hardware from the list and add its name to --alsa-output-device=

    --alsa-output-device='plug:surround21'

so your complete command will look like below,

google-chrome --window-position=0,0 --window-size=1920,1080 --alsa-output-device='plug:surround21' -kiosk https://www.youtube.com/watch?v=LTbnmiXWs2k
user_98761110

I faced the same problem while attempting to do the same. Here's what actually worked:

chrome (...) --alsa-output-device=hw:0,0
ffmpeg -f alsa -ac 2 -i hw:0,1,1 test.wav

This has chrome using (card 0, device 0) for output, which is looped back to (card 0, device 1, substream 1). The format is --alsa-output-device=hw:card,device

The opposite also works:

chrome (...) --alsa-output-device=hw:0,1
ffmpeg -f alsa -ac 2 -i hw:0,0,1 test.wav

Selecting the substream (e.g. --alsa-output-device=hw:0,1,4) is impossible. If capturing with ffmpeg just assume substream 1.

user_124688380
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