Silence detection and timestamping

Imagine there is something like civil band radio and you want to run some software overnight and have conversations logged like this:

-rw-r--r--  1 jenda jenda 183k rec-2012-08-08-18-37-37.ogg
-rw-r--r--  1 jenda jenda  98k rec-2012-08-08-18-41-49.ogg
-rw-r--r--  1 jenda jenda 100k rec-2012-08-08-18-47-35.ogg
-rw-r--r--  1 jenda jenda 200k rec-2012-08-08-18-54-52.ogg

We will use one computer for receiving and another for splitting based on silence detection.

Receiving

gnuradio-companion sketch is here. It receives narrow-band FM, but changing it for other modulations should be easy.

Create a pipe, run netcat to transmit data over the network and run the gnuradio program.

mkfifo test.wav
cat test.wav | nc 192.168.77.226 3333 &
./top_block.py

Detecting

On the other end (well, you can run everything on one computer just by piping it instead of using netcat) download and compile squelch-cut.c and run it like

nc -l -p 3333 | ./a.out

WAV (they are actually RAW) files should appear in current working directory after the first transmission occurs.

Use oggenc to encode them to some more common format.

oggenc -r -C 1 --raw-endianness 1 rec-*.wav
 
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