[nils@fyps ~]$ arecord -vvvv -fdat foo.wav
Aufnahme: WAVE 'foo.wav' : Signed 16 bit Little Endian, Rate: 48000 Hz, stereo
Plug PCM: Linear Integer <-> Linear Float conversion PCM (FLOAT_LE)
Its setup is:
  stream       : CAPTURE
  access       : RW_INTERLEAVED
  format       : S16_LE
  subformat    : STD
  channels     : 2
  rate         : 48000
  exact rate   : 48000 (48000/1)
  msbits       : 16
  buffer_size  : 18000
  period_size  : 6000
  period_time  : 125000
  tstamp_mode  : NONE
  period_step  : 1
  avail_min    : 6000
  period_event : 0
  start_threshold  : 1
  stop_threshold   : 18000
  silence_threshold: 0
  silence_size : 0
  boundary     : 5066549580791808000
Slave: Direct Snoop PCM
Its setup is:
  stream       : CAPTURE
  access       : MMAP_INTERLEAVED
  format       : FLOAT_LE
  subformat    : STD
  channels     : 2
  rate         : 48000
  exact rate   : 48000 (48000/1)
  msbits       : 32
  buffer_size  : 18000
  period_size  : 6000
  period_time  : 125000
  tstamp_mode  : NONE
  period_step  : 1
  avail_min    : 6000
  period_event : 0
  start_threshold  : 1
  stop_threshold   : 18000
  silence_threshold: 0
  silence_size : 0
  boundary     : 5066549580791808000
Hardware PCM card 1 'Loopback' device 0 subdevice 1
Its setup is:
  stream       : CAPTURE
  access       : MMAP_INTERLEAVED
  format       : FLOAT_LE
  subformat    : STD
  channels     : 2
  rate         : 48000
  exact rate   : 48000 (48000/1)
  msbits       : 32
  buffer_size  : 18000
  period_size  : 6000
  period_time  : 125000
  tstamp_mode  : ENABLE
  period_step  : 1
  avail_min    : 6000
  period_event : 0
  start_threshold  : 1
  stop_threshold   : 5066549580791808000
  silence_threshold: 0
  silence_size : 0
  boundary     : 5066549580791808000
  appl_ptr     : 0
  hw_ptr       : 0