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user:jenda:rtl-fm [2015/03/13 03:07]
jenda created
user:jenda:rtl-fm [2015/04/26 14:07] (current)
jenda
Line 1: Line 1:
 +====== rtl_fm and proper audio bandlimiting ======
  
 +rtl_fm does not properly limit audio before downsampling. You will hear annoying pitch when you set lower audio rate (e.g. 24k or 16k) - it's the aliased pilot tone. But what if you can't afford 48k audio rate, for example because you are saving the stream to a small memory card? Try proper resampling with sox.
 +
 +<​code>​rtl_fm -f 99700k -p 1 -M fm -s 144k -r 48000 -E deemp |
 + sox -t raw -r 48000 -e signed-integer -b 16 -c 1 - -t raw - vol 6 dB rate -m 16000 |
 + aplay -r 16000 -f S16_LE ​ -c 1</​code>​
 
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