Merged fir_interpolate_cc

README.md

@@ -315,7 +315,12 @@ Other parameters were explained above at `firdes_lowpass_f`.
 	fir_decimate_cc <decimation_factor> [transition_bw [window]]
 
 It is a decimator that keeps one sample out of `decimation_factor` samples.
-To avoid aliasing, it runs a filter on the signal and removes spectral components above `0.5 × nyquist_frequency × decimation_factor`.
+To avoid aliasing, it runs a filter on the signal and removes spectral components above `0.5 × nyquist_frequency × decimation_factor` from the input signal.
+
+	fir_interpolate_cc <interpolation_factor> [transition_bw [window]]
+
+It is an interpolator that generates `interpolation_factor` number of output samples from one input sample.
+To avoid aliasing, it runs a filter on the signal and removes spectral components above `0.5 × nyquist_frequency / interpolation_factor` from the output signal.
 
 `transition_bw` and `window` are the parameters of the filter.
 

csdr.c

@@ -51,6 +51,7 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <strings.h>
 #include <errno.h>
 #include "fastddc.h"
+#include <assert.h>
 
 char usage[]=
 "csdr - a simple commandline tool for Software Defined Radio receiver DSP.\n\n"
@@ -92,6 +93,7 @@ char usage[]=
 "    amdemod_cf\n"
 "    amdemod_estimator_cf\n"
 "    fir_decimate_cc <decimation_factor> [transition_bw [window]]\n"
+"    fir_interpolate_cc <interpolation_factor> [transition_bw [window]]\n"
 "    firdes_lowpass_f <cutoff_rate> <length> [window [--octave]]\n"
 "    firdes_bandpass_c <low_cut> <high_cut> <length> [window [--octave]]\n"
 "    agc_ff [hang_time [reference [attack_rate [decay_rate [max_gain [attack_wait [filter_alpha]]]]]]]\n"
@@ -1104,6 +1106,66 @@ int main(int argc, char *argv[])
 			//fprintf(stderr,"iskip=%d output_size=%d start=%x target=%x skipcount=%x \n",input_skip,output_size,input_buffer, ((complexf*)input_buffer)+(BIG_BUFSIZE-input_skip),(BIG_BUFSIZE-input_skip));
 		}
 	}
+
+	if(!strcmp(argv[1],"fir_interpolate_cc"))
+	{
+		bigbufs=1;
+
+		if(argc<=2) return badsyntax("need required parameter (interpolation factor)");
+
+		int factor;
+		sscanf(argv[2],"%d",&factor);
+		assert(factor >= 1);
+
+		float transition_bw = 0.05;
+		if(argc>=4) sscanf(argv[3],"%g",&transition_bw);
+		assert(transition_bw >= 0 && transition_bw < 1.);
+
+		window_t window = WINDOW_DEFAULT;
+		if(argc>=5)
+		{
+			window=firdes_get_window_from_string(argv[4]);
+		}
+		else fprintf(stderr,"fir_interpolate_cc: window = %s\n",firdes_get_string_from_window(window));
+
+		int taps_length=firdes_filter_len(transition_bw);
+		fprintf(stderr,"fir_interpolate_cc: taps_length = %d\n",taps_length);
+		assert(taps_length > 0);
+
+		while (env_csdr_fixed_big_bufsize < taps_length*2) env_csdr_fixed_big_bufsize*=2; //temporary fix for buffer size if [transition_bw] is low
+		//fprintf(stderr, "env_csdr_fixed_big_bufsize = %d\n", env_csdr_fixed_big_bufsize);
+
+		if(!initialize_buffers()) return -2;
+		sendbufsize(the_bufsize*factor);
+		assert(the_bufsize > 0);
+
+		float *taps;
+		taps=(float*)malloc(taps_length*sizeof(float));
+		assert(taps);
+
+		firdes_lowpass_f(taps,taps_length,0.5/(float)factor,window);
+
+		int input_skip=0;
+		int output_size=0;
+		float* interp_output_buffer = (float*)malloc(sizeof(float)*2*the_bufsize*factor);
+		for(;;)
+		{
+			FEOF_CHECK;
+			output_size=fir_interpolate_cc((complexf*)input_buffer, (complexf*)interp_output_buffer, the_bufsize, factor, taps, taps_length);
+			//fprintf(stderr, "os %d\n",output_size);
+			fwrite(interp_output_buffer, sizeof(complexf), output_size, stdout);
+			fflush(stdout);
+			TRY_YIELD;
+			input_skip=output_size/factor;
+			memmove((complexf*)input_buffer,((complexf*)input_buffer)+input_skip,(the_bufsize-input_skip)*sizeof(complexf)); //memmove lets the source and destination overlap
+			fread(((complexf*)input_buffer)+(the_bufsize-input_skip), sizeof(complexf), input_skip, stdin);
+			//fprintf(stderr,"iskip=%d output_size=%d start=%x target=%x skipcount=%x \n",input_skip,output_size,input_buffer, ((complexf*)input_buffer)+(BIG_BUFSIZE-input_skip),(BIG_BUFSIZE-input_skip));
+		}
+	}
+
+
+
+
 	/*if(!strcmp(argv[1],"ejw_test"))
 	{
 		printf("ejqd=[");

libcsdr.c

@@ -580,6 +580,34 @@ int fir_decimate_cc(complexf *input, complexf *output, int input_size, int decim
 }
 */
 
+int fir_interpolate_cc(complexf *input, complexf *output, int input_size, int interpolation, float *taps, int taps_length)
+{
+	//i:  input index
+	//oi: output index
+	//ti: tap index
+	//ti: secondary index (inside filter function)
+	//ip: interpolation phase (0 <= ip < interpolation)
+	int oi=0;
+	for(int i=0; i<input_size; i++) //@fir_interpolate_cc: outer loop
+	{
+		if(i*interpolation + (interpolation-1) + taps_length > input_size*interpolation) break;
+		for(int ip=0; ip<interpolation; ip++)
+		{
+			float acci=0;
+			float accq=0;
+			//int tistart = (interpolation-ip)%interpolation; 
+			int tistart = (interpolation-ip); //why does this work? why don't we need the % part?
+			for(int ti=tistart, si=0; ti<taps_length; (ti+=interpolation), (si++)) acci += (iof(input,i+si)) * taps[ti]; //@fir_interpolate_cc: i loop
+			for(int ti=tistart, si=0; ti<taps_length; (ti+=interpolation), (si++)) accq += (qof(input,i+si)) * taps[ti]; //@fir_interpolate_cc: q loop
+			iof(output,oi)=acci;
+			qof(output,oi)=accq;
+			oi++;
+		}
+	}
+	return oi;
+}
+
+
 rational_resampler_ff_t rational_resampler_ff(float *input, float *output, int input_size, int interpolation, int decimation, float *taps, int taps_length, int last_taps_delay)
 {
 

libcsdr.h

@@ -102,6 +102,7 @@ void limit_ff(float* input, float* output, int input_size, float max_amplitude);
 //filters, decimators, resamplers, shift, etc.
 float fir_one_pass_ff(float* input, float* taps, int taps_length);
 int fir_decimate_cc(complexf *input, complexf *output, int input_size, int decimation, float *taps, int taps_length);
+int fir_interpolate_cc(complexf *input, complexf *output, int input_size, int interpolation, float *taps, int taps_length);
 int deemphasis_nfm_ff (float* input, float* output, int input_size, int sample_rate);
 float deemphasis_wfm_ff (float* input, float* output, int input_size, float tau, int sample_rate, float last_output);
 float shift_math_cc(complexf *input, complexf* output, int input_size, float rate, float starting_phase);