Big rtl_fm (and more) improvements, testing requested
deron at pagestream.org
Wed Dec 18 16:23:45 UTC 2013
I had a chance to place with it this weekend, and again last night, and
the only additional problems I had:
- After 20-30 forced quits, the device will go completely bonkers. Ok,
not very technical and hopefully related to the inability to stop it in
- I have no idea how to make scanning work. Is there something I am
missing to force it to continue scanning at the next frequency? Also,
when it finds something that breaks squelch, could it dump to shell the
frequency using stderr?
- I'm using an R820T based device. As I understand it, the offset tuning
is unnecessary. Looking at the code, "-E offset" should do just what I
want. It disables the offset/90deg shift in rtl_fm, and the library
recognizes that is unnecessary and returns -2 or some such. The (very
minor) bug is that it reports it as an error that it is unable to set
So what can I do to help find/fix the quit problem?
Some very basic observations, hope they are useful. Some may be a result
of my (lack of) understanding.
- Control-c will not stop it. It catches the signal, and reports "Signal
caught, exiting!" but does not. I had to kill -9 to stop it...
- When first run, I get 30 logged errors of "xhci_hcd 0000:00:14.0:
ERROR no room on ep ring".
- fm was much better than the old version, but -fmwb was the same. I
narrowed it down to -o 4. That alone destroyed all improvements. By using:
./rtl_fm -f 95.1M -M fm -s 170k -A fast -r 32k -l 0 -E deemp - |
aplay -r 32k -f S16_LE
It was much better. I'll play around more this weekend when I have more
Overall, very good. Night and day compared to before. Also, cpu usage
seemed less. Top reports about 3% vs 6% from before.
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