Banana Pi BPI-M1 Manual page 28

BPI-M1 MIC
Client:
# netcat <banana ip> 9000 | vlc
Works? Great! Live listening is important to play around and test the mic.
Listen and record at same time
# rec -c 2 -C 64 -t mp3 - | tee test.mp3 | netcat -l -p 9000
Poor man's streaming server
# apt-get install openbsd-inetd tcpd
Edit config file:
# nano /etc/inetd.conf
Insert this at the end:
9000 stream tcp nowait nobody /usr/bin/tail tail -f /test.mp3
Restart service
# service openbsd-inetd restart
Start recording on banana:
# rec -c 2 -C 64 /test.mp3
Connect via client:
# netcat <banana ip> 9000 | vlc -
C. Advanced Recording
Devide recording and postprocessing in two parts
# rec -t raw - remix - | sox -t raw -r 48000 -c 1 -b 16 -e signed-integer - -t mp3 -c 1 -C 32 test.mp3
Recording:
-t raw - forward raw input to pipe
remix - Mix the two channels to one
Encoding:
-t raw -r 48000 -c 1 -b 16 -e signed-integer - tell sox what kind of strean comes from stdin
-t mp3 -c 1 -C 32 test.mp3 and what goes out
Note that it is switched to mono from here with -c 1 and the mp3 bitrate is cut in half. Live listening to the strean does not
work anymore, i asume it is because of the non regulare output from pipeing and processing in a second step.
Reduce noise
The mic input is pretty bad, lot of white noise. Sox can deal with it.
Make a sample "silent" file:
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