alsa kopirovani zvuku z jedne karty do druhe.

$ export LANG=C

$ cat /proc/asound/cards
 0 [HDMI           ]: HDA-Intel - HDA Intel HDMI
                      HDA Intel HDMI at 0xf7d14000 irq 32
 1 [PCH            ]: HDA-Intel - HDA Intel PCH
                      HDA Intel PCH at 0xf7d10000 irq 30
 2 [F1005          ]: USB-Audio - FaceCam 1005
                      KYE Systems Corp. FaceCam 1005 at usb-0000:00:14.0-3, high speed

$ arecord -l
**** List of CAPTURE Hardware Devices ****
card 1: PCH [HDA Intel PCH], device 0: ALC892 Analog [ALC892 Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 2: ALC892 Alt Analog [ALC892 Alt Analog]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 2: F1005 [FaceCam 1005], device 0: USB Audio [USB Audio]
  Subdevices: 1/1
  Subdevice #0: subdevice #0

$ aplay -l
**** List of PLAYBACK Hardware Devices ****
card 0: HDMI [HDA Intel HDMI], device 3: HDMI 0 [HDMI 0]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: HDMI [HDA Intel HDMI], device 7: HDMI 1 [HDMI 1]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 0: HDMI [HDA Intel HDMI], device 8: HDMI 2 [HDMI 2]
  Subdevices: 1/1
  Subdevice #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 0: ALC892 Analog [ALC892 Analog]
  Subdevices: 0/1
  Subdevice #0: subdevice #0
card 1: PCH [HDA Intel PCH], device 1: ALC892 Digital [ALC892 Digital]
  Subdevices: 1/1
  Subdevice #0: subdevice #0



arecord -fdat -Dplug:dsnoop:F1005 | aplay -Dplug:dmix:PCH
arecord -fdat -D "plug:\"dsnoop:2,0\"" | aplay -D "plug:\"dmix:1,0\""


sox --buffer 2048 -r 48000 -t alsa plug:dsnoop:F1005 -t alsa plug:dmix:PCH
sox --buffer 2048 -r 48000 -t alsa "plug:\"dsnoop:2,0\"" -t alsa "plug:\"dmix:1,0\""


# soucasne prehravani a nahravani do wavu:
arecord -fdat -Dplug:dsnoop:F1005 | aplay -Dplug:dmix:PCH
arecord -f dat -d 20 -Dplug:dsnoop:F1005 /tmp/test.wav
# jeden prikaz:
arecord -fdat -Dplug:dsnoop:F1005 | tee /tmp/test.wav | aplay -Dplug:dmix:PCH



# Alsa usually builds a chain like plug->dmix->hw where "type plug" is an autoconversion module, converting whatever input format into a supported output format, and "type dmix" is a module to mix output of multiple apps into a single "hw" stream, since most cards don't have hardware mixing and only support one audio stream

# "dsnoop" is kind of anti-dmix, it allows multiple apps to get the sound from a single hardware stream

# To have a lower latency you can try sox.