$ ALSA_CONFIG_PATH=/usr/share/alsa/alsa.conf:./dumpasoundrc /home/pi/special/ffmpeg/ffmpeg -f alsa -acodec pcm_s32le -i michooks -f null -
ffmpeg version git-2017-02-05-e57fd92 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 4.9.2 (Raspbian 4.9.2-10)
  configuration: --extra-cflags=-I/opt/vc/include/IL --enable-nonfree --enable-omx-rpi --logfile=CONFIG.TXT
  libavutil      55. 46.100 / 55. 46.100
  libavcodec     57. 75.100 / 57. 75.100
  libavformat    57. 66.101 / 57. 66.101
  libavdevice    57.  2.100 / 57.  2.100
  libavfilter     6. 73.100 /  6. 73.100
  libswscale      4.  3.101 /  4.  3.101
  libswresample   2.  4.100 /  2.  4.100
[ALSA Debug Hook] Installing hooks.
Hooks PCM
Slave: Soft volume PCM
Control: Boost Capture Volume
min_dB: -3
max_dB: 50
resolution: 256
Slave: Route conversion PCM
  Transformation table:
    0 <- 0
    1 <- 0
Slave: Mmap emulation PCM
Slave: Hardware PCM card 1 'mems-mic' device 0 subdevice 0
[ALSA Debug Hook] hw_params:
Hooks PCM
Slave: Soft volume PCM
Control: Boost Capture Volume
min_dB: -3
max_dB: 50
resolution: 256
Its setup is:
  stream       : CAPTURE
  access       : RW_INTERLEAVED
  format       : S32_LE
  subformat    : STD
  channels     : 2
  rate         : 48000
  exact rate   : 48000 (48000/1)
  msbits       : 32
  buffer_size  : 65536
  period_size  : 16384
  period_time  : 341333
  tstamp_mode  : NONE
  period_step  : 1
  avail_min    : 16384
  period_event : 0
  start_threshold  : 1
  stop_threshold   : 65536
  silence_threshold: 0
  silence_size : 0
  boundary     : 1073741824
Slave: Route conversion PCM
  Transformation table:
    0 <- 0
    1 <- 0
Its setup is:
  stream       : CAPTURE
  access       : MMAP_INTERLEAVED
  format       : S32_LE
  subformat    : STD
  channels     : 2
  rate         : 48000
  exact rate   : 48000 (48000/1)
  msbits       : 32
  buffer_size  : 65536
  period_size  : 16384
  period_time  : 341333
  tstamp_mode  : NONE
  period_step  : 1
  avail_min    : 16384
  period_event : 0
  start_threshold  : 1
  stop_threshold   : 65536
  silence_threshold: 0
  silence_size : 0
  boundary     : 1073741824
Slave: Mmap emulation PCM
Its setup is:
  stream       : CAPTURE
  access       : MMAP_INTERLEAVED
  format       : S32_LE
  subformat    : STD
  channels     : 2
  rate         : 48000
  exact rate   : 48000 (48000/1)
  msbits       : 32
  buffer_size  : 65536
  period_size  : 16384
  period_time  : 341333
  tstamp_mode  : NONE
  period_step  : 1
  avail_min    : 16384
  period_event : 0
  start_threshold  : 1
  stop_threshold   : 65536
  silence_threshold: 0
  silence_size : 0
  boundary     : 1073741824
Slave: Hardware PCM card 1 'mems-mic' device 0 subdevice 0
Its setup is:
  stream       : CAPTURE
  access       : RW_INTERLEAVED
  format       : S32_LE
  subformat    : STD
  channels     : 2
  rate         : 48000
  exact rate   : 48000 (48000/1)
  msbits       : 32
  buffer_size  : 65536
  period_size  : 16384
  period_time  : 341333
  tstamp_mode  : NONE
  period_step  : 1
  avail_min    : 16384
  period_event : 0
  start_threshold  : 1073741824
  stop_threshold   : 65536
  silence_threshold: 0
  silence_size : 0
  boundary     : 1073741824
  appl_ptr     : 0
  hw_ptr       : 0
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, alsa, from 'michooks':
  Duration: N/A, start: 1487306487.586316, bitrate: 3072 kb/s
    Stream #0:0: Audio: pcm_s32le, 48000 Hz, stereo, s32, 3072 kb/s
Output #0, null, to 'pipe:':
  Metadata:
    encoder         : Lavf57.66.101
    Stream #0:0: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
    Metadata:
      encoder         : Lavc57.75.100 pcm_s16le
Stream mapping:
  Stream #0:0 -> #0:0 (pcm_s32le (native) -> pcm_s16le (native))
Press [q] to stop, [?] for help
size=N/A time=00:00:16.54 bitrate=N/A speed=   1x