rtl_fm problem with capture audio

keenerd keenerd at gmail.com
Thu Nov 29 18:28:05 UTC 2012


On 11/29/12, Pete Zaitcev <zaitcev at kotori.zaitcev.us> wrote:
> But another thing is that rtl_fm just won't work until the signal is
> strong enough.

Maybe you should try increasing the gain.

> Final command line was this:
> rtl_fm -l 0 -f 99.5e6 -N -s 170e3 -o 4 -A -r 24e3 - | \
> aplay -r 24k -f S16_LE -t raw -c 1

Really, much smarter to use -W instead.  You are losing a moderate
amount of the signal.  First, wbfm is slightly off center pushing 10%
of the signal out of range.  Second, it carries audio information up
to 16kHz and resampling at 24ks/s discards another 25%.

rtl_fm -W -f 99.5e6 -g 49 | aplay -r 32k -f S16_LE -t raw -c 1

will work better.  No reason to spell it out the long way.

-Kyle




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