$ ALSA_CONFIG_PATH=/usr/share/alsa/alsa.conf:./dumpasoundrc  /home/pi/special/ffmpeg/ffmpeg -v 9 -loglevel 99  -f alsa -acodec pcm_s32le -i michooks -c copy -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
Splitting the commandline.
Reading option '-v' ... matched as option 'v' (set logging level) with argument '9'.
Reading option '-loglevel' ... matched as option 'loglevel' (set logging level) with argument '99'.
Reading option '-f' ... matched as option 'f' (force format) with argument 'alsa'.
Reading option '-acodec' ... matched as option 'acodec' (force audio codec ('copy' to copy stream)) with argument 'pcm_s32le'.
Reading option '-i' ... matched as input url with argument 'michooks'.
Reading option '-c' ... matched as option 'c' (codec name) with argument 'copy'.
Reading option '-f' ... matched as option 'f' (force format) with argument 'null'.
Reading option '-' ... matched as output url.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option v (set logging level) with argument 9.
Successfully parsed a group of options.
Parsing a group of options: input url michooks.
Applying option f (force format) with argument alsa.
Applying option acodec (force audio codec ('copy' to copy stream)) with argument pcm_s32le.
Successfully parsed a group of options.
Opening an input file: michooks.
[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
[alsa @ 0x1e59460] All info found
[alsa @ 0x1e59460] stream 0: start_time: 1487397416.759 duration: -9223372036854.775
[alsa @ 0x1e59460] format: start_time: 1487397416.759 duration: -9223372036854.775 bitrate=3072 kb/s
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, alsa, from 'michooks':
  Duration: N/A, start: 1487397416.759089, bitrate: 3072 kb/s
    Stream #0:0, 1, 1/1000000: Audio: pcm_s32le, 48000 Hz, stereo, s32, 3072 kb/s
Successfully opened the file.
Parsing a group of options: output url -.
Applying option c (codec name) with argument copy.
Applying option f (force format) with argument null.
Successfully parsed a group of options.
Opening an output file: -.
Successfully opened the file.
Output #0, null, to 'pipe:':
  Metadata:
    encoder         : Lavf57.66.101
    Stream #0:0, 0, 1/1000000: Audio: pcm_s32le, 48000 Hz, stereo, s32, 3072 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
Press [q] to stop, [?] for help
cur_dts is invalid (this is harmless if it occurs once at the start per stream)
[null @ 0x1e66760] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 9407813 >= 9404054
[null @ 0x1e66760] Application provided invalid, non monotonically increasing dts to muxer in stream 0: 11145066 >= 11141239
size=N/A time=00:00:17.01 bitrate=N/A speed=   1x
video:0kB audio:6382kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: unknown
Input file #0 (michooks):
  Input stream #0:0 (audio): 35966 packets read (6535248 bytes);
  Total: 35966 packets (6535248 bytes) demuxed
Output file #0 (pipe:):
  Output stream #0:0 (audio): 35966 packets muxed (6535248 bytes);
  Total: 35966 packets (6535248 bytes) muxed
0 frames successfully decoded, 0 decoding errors