added ddc_transition_bw()

README.md

@@ -47,6 +47,12 @@ The filter envelope can be dragged at its ends and moved around to set the passb
 
 However, if you hold the shift key, you can drag the center line (BFO) or the whole passband (PBS).
 
+## Configuration tips
+
+If you want to run OpenWebRX on a remote server instead of localhost, do not forget to set *server_hostname* in `config_webrx.py`, or you may get a WebSocket error.
+
+DSP CPU usage can be fine-tuned in `plugins/dsp/csdr/plugin.py`: you can set transition bandwidths higher (thus degrade filter performance by decreasing the length of the kernel, but also decrease CPU usage).
+
 ## Todo
 
 Currently, clients use up a lot of bandwidth. This will be improved later.

config_webrx.py

@@ -53,7 +53,7 @@ center_freq = 145525000
 rf_gain = 5
 
 start_rtl_thread=True #rtl_sdr is more stable than rtl_tcp...
-start_rtl_command="rtl_sdr -s {samp_rate} -f {center_freq}  - | nc -vvl 127.0.0.1 8888".format(rf_gain=rf_gain, center_freq=center_freq, samp_rate=samp_rate) 
+start_rtl_command="rtl_sdr -s {samp_rate} -f {center_freq}  - | nc -vvl 127.0.0.1 -p 8888".format(rf_gain=rf_gain, center_freq=center_freq, samp_rate=samp_rate) 
 #start_rtl_tcp_command="rtl_tcp -s 250000 -f 145525000 -g 0 -p 8888"
 #You can use other SDR hardware as well, but if the command above outputs samples in a format other than [unsigned char], then the dsp plugin has to be slightly modified (at the csdr convert_u8_f part).
 

plugins/dsp/csdr/plugin.py

@@ -14,8 +14,9 @@ class dsp_plugin:
 		self.low_cut = -4000
 		self.high_cut = 4000
 		self.bpf_transition_bw = 300 #Hz, and this is a constant
+		self.ddc_transition_bw_rate = 0.15 # of the IF sample rate
 		self.running = False
-		chain_begin="nc localhost 4951 | csdr convert_u8_f | csdr shift_addition_cc --fifo {shift_pipe} | csdr fir_decimate_cc {decimation} 0.005 HAMMING | csdr bandpass_fir_fft_cc --fifo {bpf_pipe} {bpf_transition_bw} HAMMING | "
+		chain_begin="nc localhost 4951 | csdr convert_u8_f | csdr shift_addition_cc --fifo {shift_pipe} | csdr fir_decimate_cc {decimation} {ddc_transition_bw} HAMMING | csdr bandpass_fir_fft_cc --fifo {bpf_pipe} {bpf_transition_bw} HAMMING | "
 		self.chains = {
 			"nfm" :  chain_begin + "csdr fmdemod_quadri_cf | csdr limit_ff | csdr fractional_decimator_ff {last_decimation} | csdr deemphasis_nfm_ff 48000 | csdr fastagc_ff | csdr convert_f_i16",
 			"am" :  chain_begin + "csdr amdemod_cf | csdr fastdcblock_ff | csdr fractional_decimator_ff {last_decimation} | csdr agc_ff | csdr limit_ff | csdr convert_f_i16",
@@ -85,6 +86,9 @@ class dsp_plugin:
 			pass
 		os.mkfifo(path)	
 
+	def ddc_transition_bw(self):
+		return self.ddc_transition_bw_rate*(self.if_samp_rate()/float(self.samp_rate))
+
 	def start(self):
 		command_base=self.chains[self.demodulator]
 		
@@ -99,7 +103,7 @@ class dsp_plugin:
 			self.mkfifo(self.shift_pipe)
 
 		#run the command
-		command=command_base.format(bpf_pipe=self.bpf_pipe,shift_pipe=self.shift_pipe,decimation=self.decimation,last_decimation=self.last_decimation,fft_size=self.fft_size,fft_block_size=self.fft_block_size(),bpf_transition_bw=float(self.bpf_transition_bw)/self.if_samp_rate())
+		command=command_base.format(bpf_pipe=self.bpf_pipe,shift_pipe=self.shift_pipe,decimation=self.decimation,last_decimation=self.last_decimation,fft_size=self.fft_size,fft_block_size=self.fft_block_size(),bpf_transition_bw=float(self.bpf_transition_bw)/self.if_samp_rate(),ddc_transition_bw=self.ddc_transition_bw())
 		print "[openwebrx-dsp-plugin:csdr] Command =",command
 		#code.interact(local=locals())
 		self.process = subprocess.Popen(command, stdout=subprocess.PIPE, shell=True)