[LAD] simple silence detection tool

[Jeremy Hansen]

On Feb 10, 2013, at 8:16 AM, Robin Gareus <robin at gareus.org> wrote:

> On 02/10/2013 08:38 AM, Jeremy Hansen wrote:
>> 
>> I'm looking for a simple tool where I can point it at an http audio
>> stream, define a number of seconds to detect silence and exit with a
>> non-zero status if silence is detected.  It seems like this should be
>> easy but I've been search high and low for such a utility and nothing
>> simple exists.  Unfortunately I'm not much of a developer, but this
>> doesn't seem like it would be that difficult.  Maybe it's harder than
>> I think, hence no tool that I can find.
> 
> https://github.com/x42/silan may do the job. It prints ranges or silence
> in a file or stream (incl. mp3,aac,wma,ogg,m4a,.. decoding and http,
> rtmp stream support thanks to libav/ffmpeg). It is used by airtime
> (sourcefabric's radio) to highlight silent ranges.
> 
> silan -t 0.1 -s -60d "http://mp2.somafm.com:9016" \
> |  grep -quiet "Sound Off" \
> && echo " do something"

This is strange.  This works, but I'm unable to grep the output and I'm not sure why.  If I pipe to grep, I get nothing.  I tried redirecting stderr to stdout and doesn't seem to work.

[jeremy at serv src]$ ./silan -t 2.0 -s -40d "http://live.skidrowstudios.com:8000/live"
Info: signal threshold: 0.010000 ^= -40.000dBFS
0.069569 Sound On
15.814150 Sound Off

Doing the same test:

[jeremy at serv src]$ ./silan -t 2.0 -s -40d "http://live.skidrowstudios.com:8000/live" | grep "Sound Off"
Info: signal threshold: 0.010000 ^= -40.000dBFS


I get nothing.

Thanks
-jeremy