Translation von IQ-Signalen

iq/shift_IQ.c

@@ -0,0 +1,163 @@
+
+/*
+ *  ./shift <IQ.wav> [freq] [> IQ_translated.wav]
+ */
+
+/*
+    sdrsharpIQ.wav = conj(rtlsdrIQ.wav)  ->  rtlsdrIQ.wav: swapIQ
+*/
+/*
+    time domain                       frequency domain
+    w(t) = exp(t*i*2pi*f0)*z(t)  <->  W(f) = Z(f-f0)
+
+    z = x + iy
+    w = u + iv = exp(ia)*z
+    u = x*cos(a) - y*sin(a);
+    v = x*sin(a) + y*cos(a);
+    
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <complex.h>
+
+
+#define  PI  (3.1415926535897932384626433832795)
+
+int sample_rate, bits_sample;
+
+
+int findstr(char *buff, char *str, int pos) {
+    int i;
+    for (i = 0; i < 4; i++) {
+        if (buff[(pos+i)%4] != str[i]) break;
+    }
+    return i;
+}
+int read_IQwavheader(FILE *fp, int *sample_rate, int *bits_sample, FILE *fout) {
+    int channels = 0;
+    char txt[4+1] = "\0\0\0\0";
+    unsigned char dat[4];
+    int byte, p=0;
+
+    if (fread(txt, 1, 4, fp) < 4) return -1; else fwrite(txt, 1, 4, fout);
+    if (strncmp(txt, "RIFF", 4)) return -1;
+
+    // pos_WAVE = 8L
+    if (fread(txt, 1, 4, fp) < 4) return -1; else fwrite(txt, 1, 4, fout);
+    if (fread(txt, 1, 4, fp) < 4) return -1; else fwrite(txt, 1, 4, fout);
+    if (strncmp(txt, "WAVE", 4)) return -1;
+
+    // pos_fmt = 12L
+    for ( ; ; ) {
+        if ( (byte=fgetc(fp)) == EOF ) return -1; else fprintf(fout, "%c", byte & 0xFF);
+        txt[p % 4] = byte;
+        p++; if (p==4) p=0;
+        if (findstr(txt, "fmt ", p) == 4) break;
+    }
+    
+    if (fread(dat, 1, 4, fp) < 4) return -1; else fwrite(dat, 1, 4, fout);
+    if (fread(dat, 1, 2, fp) < 2) return -1; else fwrite(dat, 1, 2, fout);
+
+    if (fread(dat, 1, 2, fp) < 2) return -1; else fwrite(dat, 1, 2, fout);
+    channels = dat[0] + (dat[1] << 8);
+
+    if (fread(dat, 1, 4, fp) < 4) return -1; else fwrite(dat, 1, 4, fout);
+    *sample_rate = dat[0] | (dat[1] << 8) | (dat[2] << 16) | (dat[3] << 24); //memcpy(&sr, dat, 4);
+
+    if (fread(dat, 1, 4, fp) < 4) return -1; else fwrite(dat, 1, 4, fout);
+    if (fread(dat, 1, 2, fp) < 2) return -1; else fwrite(dat, 1, 2, fout);
+
+    if (fread(dat, 1, 2, fp) < 2) return -1; else fwrite(dat, 1, 2, fout);
+    *bits_sample = dat[0] + (dat[1] << 8);
+
+    // pos_dat = 36L + info
+    for ( ; ; ) {
+        if ( (byte=fgetc(fp)) == EOF ) return -1; else fprintf(fout, "%c", byte & 0xFF);
+        txt[p % 4] = byte;
+        p++; if (p==4) p=0;
+        if (findstr(txt, "data", p) == 4) break;
+    }
+    if (fread(dat, 1, 4, fp) < 4) return -1; else fwrite(dat, 1, 4, fout);
+
+
+    fprintf(stderr, "sample_rate: %d\n", *sample_rate);
+    fprintf(stderr, "bits       : %d\n", *bits_sample);
+    fprintf(stderr, "channels   : %d\n", channels);
+
+    if ((*bits_sample != 8) && (*bits_sample != 16)) return -2;
+    if (channels != 2) return -3;
+
+    return 0;
+}
+
+int read_csample(FILE *fp, double complex *z) {
+    short x, y;
+
+    if (fread( &x, bits_sample/8, 1, fp) != 1) return EOF;
+    if (fread( &y, bits_sample/8, 1, fp) != 1) return EOF;
+
+    *z = x + I*y;
+
+    if (bits_sample == 8) {
+        *z -= 128 + I*128;
+    }
+
+    return 0;
+}
+
+int write_csample(FILE *fp, double complex w) {
+    int u, v;
+
+    if (bits_sample == 8) {
+        w += 128 + I*128;
+    }
+
+    u = creal(w);
+    v = cimag(w);
+                                        // 16 bit  (short)  ->  (int)
+    fwrite( &u, bits_sample/8, 1, fp);  // +  0000 .. 7FFF  ->  0000 0000 .. 0000 7FFF
+    fwrite( &v, bits_sample/8, 1, fp);  // -  8000 .. FFFF  ->  FFFF 8000 .. FFFF FFFF
+
+    return 0;
+
+}
+
+
+int main(int argc, char *argv[]) {
+    FILE *fp, *fout;
+    int sample = 0;
+    double t, f = 0;
+    double complex  z, w;
+
+    if (argv[1]) {
+        
+        fp = fopen(argv[1], "rb");
+        if (fp == NULL) return -1;
+
+        fout = stdout; //fopen("tmp_out.wav", "wb");
+        read_IQwavheader(fp, &sample_rate, &bits_sample, fout);
+
+        if (argv[2]) f = (double)atoi(argv[2]);  // f0
+
+        sample = 0;
+        for ( ; ; ) {
+
+            if (read_csample(fp, &z) == EOF) break;
+
+            t = (double)sample / sample_rate;
+            w = cexp(t*2*PI*f*I) * z;
+
+            write_csample(fout, w);
+            sample++;
+
+        }
+
+        fclose(fp);
+        fclose(fout);
+    }
+
+    return 0;
+}
+