I do have a Matrix Creator on a Raspberry pi where the /etc/asound.conf looks like:

pcm.!default {
    type hw
    card 0
}

ctl.!default {
        type hw
        card 0
}

pcm.sc {
    type hw
    card 1
    format S16_LE
    channels 1
    rate 16000
}

pcm.mic_channel0 {
  type file
  file "/tmp/matrix_micarray_channel_0"
  infile "/tmp/matrix_micarray_channel_0"
  format "raw"
  slave {
    pcm sc
  }
}

I can record and play sound through these commands:

arecord -f S16_LE -r 16000 -d 10 -D plug:mic_channel0 test.wav
aplay test.wav

but this command from the Streaming audio Tutorial

gst-launch-0.10 alsasrc device=plug:mic_channel0 ! audioconvert ! audioresample ! alsasink 

unfortunatly doesn't work. It gives me this output:

Setting pipeline to PAUSED ...
Pipeline is live and does not need PREROLL ...
Setting pipeline to PLAYING ...
New clock: GstAudioSrcClock
gst-launch-0.10: pcm_file.c:397: snd_pcm_file_add_frames: Assertion `file->wbuf_used_bytes < file->wbuf_size_bytes' 
failed.
Aborted

also a audio_capture roslaunch like:

roslaunch audio_capture capture_wave.launch device:="plug:mic_channel0"

ends with this error message:

process[audio_capture-2]: started with pid [4427]
[ERROR] [1512041350.206905657]: gstreamer: Could not open audio device for recording.
terminate called after throwing an instance of 
'boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<boost::lock_error> >'
  what():  boost: mutex lock failed in pthread_mutex_lock: Invalid argument
[audio_capture-2] process has died [pid 4427, exit code -6, cmd 
/home/roboy/workspace/devel/lib/audio_capture/audio_capture __name:=audio_capture 
__log:=/root/.ros/log/ae316724-d5c1-11e7-b8ef-b827eb26edd2/audio_capture-2.log].
log file: /root/.ros/log/ae316724-d5c1-11e7-b8ef-b827eb26edd2/audio_capture-2*.log

Since I'm in the end able to record sound from the microphones, it should also be possible to tell the gstreamer to access the mic data. But since now I don't know how, and the big master Google couldn't help me either. Does anyone know how to solve this problem? Or at least has better google skills?