Accessing OpenWebRX SDR Stream via Linux Command line and MPlayer

G'Day Guys,

In my previous posts I outlined decoding APRS using Direwolf from an audio feed extracted from my OpenWebRX Stream using the CSDR command line tools.

The following is an update on the calculations for parameters needed for the CSDR commands and I've provided an improved NFM (actually what OpenWebRX uses) as the NFM_OLD was just not 100% clear or right and I could not work it out.

I've also included USB too.

       

export SDR_SAMPLE_RATE=5000000
export SDR_GAIN=IFGR=35,RFGR=2
export AUDIO_SAMPLE_RATE=11025
export AUDIO_GAIN=0.42
export FREQ_CENTER=145500000
export FREQ_MON=145175000
export FREQ_MON_BW=12000
export FIR_DISC_FACTOR=`python -c "print float($SDR_SAMPLE_RATE)/float($AUDIO_SAMPLE_RATE)"`
export FIR_DISC_TRANS_BW=`python -c "print float($FREQ_MON_BW)/float($SDR_SAMPLE_RATE)"`
export SHFT_ADD_PIPE=/tmp/rigctrld_openwebrx_shift_pipe
export SHFT_ADD=`python -c "print float($FREQ_CENTER-($FREQ_MON))/$SDR_SAMPLE_RATE"`
export NFM_LOW_CUT_FREQ=-4000
export NFM_LOW_CUT=`python -c "print float($NFM_LOW_CUT_FREQ)/$AUDIO_SAMPLE_RATE"`
export NFM_HIGH_CUT_FREQ=4000
export NFM_HIGH_CUT=`python -c "print float($NFM_HIGH_CUT_FREQ)/$AUDIO_SAMPLE_RATE"`
export FIR_NFM_TRANS_BW=`python -c "print (float($NFM_HIGH_CUT_FREQ) - float($NFM_LOW_CUT_FREQ))/float($AUDIO_SAMPLE_RATE)"`
export FIR_DSSB_BW=4800
export SSB_LOW_CUT_FREQ=300
export SSB_LOW_CUT=`python -c "print float($SSB_LOW_CUT_FREQ)/$AUDIO_SAMPLE_RATE"`
export SSB_HIGH_CUT_FREQ=3000
export SSB_HIGH_CUT=`python -c "print float($SSB_HIGH_CUT_FREQ)/$AUDIO_SAMPLE_RATE"`
export FIR_SSB_TRANS_BW=`python -c "print (float($SSB_HIGH_CUT_FREQ) - float($SSB_LOW_CUT_FREQ))/float($AUDIO_SAMPLE_RATE)"`


# NEW NFM
nc -v 127.0.0.1 4951 | csdr shift_addition_cc $SHFT_ADD  | csdr fir_decimate_cc $FIR_DISC_FACTOR $FIR_DISC_TRANS_BW HAMMING | csdr bandpass_fir_fft_cc $NFM_LOW_CUT $NFM_HIGH_CUT $FIR_NFM_TRANS_BW HAMMING | csdr fmdemod_quadri_cf | csdr limit_ff | csdr old_fractional_decimator_ff 1.00158333333 | csdr deemphasis_nfm_ff 11025 | csdr fastagc_ff 1024 | csdr gain_ff $AUDIO_GAIN | csdr convert_f_s16 | mplayer -quiet -rawaudio samplesize=2:channels=1:rate=$AUDIO_SAMPLE_RATE -demuxer rawaudio 

# OLD NFM
nc -v 127.0.0.1 4951 | csdr shift_addition_cc $SHFT_ADD | csdr fir_decimate_cc $FIR_DISC_FACTOR $FIR_DISC_TRANS_BW HAMMING | csdr fmdemod_quadri_cf | csdr limit_ff | csdr deemphasis_nfm_ff $AUDIO_SAMPLE_RATE | csdr fastagc_ff | csdr gain_ff $AUDIO_GAIN | csdr convert_f_s16 |  mplayer -quiet -rawaudio samplesize=2:channels=1:rate=$AUDIO_SAMPLE_RATE -demuxer rawaudio -

# USB
nc -v 127.0.0.1 4951 | csdr shift_addition_cc $SHFT_ADD | csdr fir_decimate_cc $FIR_DISC_FACTOR $FIR_DISC_TRANS_BW HAMMING | csdr bandpass_fir_fft_cc $SSB_LOW_CUT $SSB_HIGH_CUT $FIR_SSB_TRANS_BW | csdr realpart_cf | csdr agc_ff | csdr limit_ff | csdr gain_ff $AUDIO_GAIN | csdr convert_f_s16 |  mplayer -quiet -rawaudio samplesize=2:channels=1:rate=$AUDIO_SAMPLE_RATE -demuxer rawaudio -