avfilter/af_aiir: factor out response calculation

libavfilter/af_aiir.c

@@ -737,41 +737,24 @@ static void draw_line(AVFrame *out, int x0, int y0, int x1, int y1, uint32_t col
     }
 }
 
-static void draw_response(AVFilterContext *ctx, AVFrame *out)
+static void get_response(int channel, int format, double w,
+                         const double *b, const double *a,
+                         int nb_b, int nb_a, double *r, double *i)
 {
-    AudioIIRContext *s = ctx->priv;
-    float *mag, *phase, *delay, min = FLT_MAX, max = FLT_MIN;
-    float min_delay = FLT_MAX, max_delay = FLT_MIN;
-    int prev_ymag = -1, prev_yphase = -1, prev_ydelay = -1;
-    char text[32];
-    int ch, i, x;
-
-    memset(out->data[0], 0, s->h * out->linesize[0]);
-
-    phase = av_malloc_array(s->w, sizeof(*phase));
-    mag = av_malloc_array(s->w, sizeof(*mag));
-    delay = av_malloc_array(s->w, sizeof(*delay));
-    if (!mag || !phase || !delay)
-        goto end;
-
-    ch = av_clip(s->ir_channel, 0, s->channels - 1);
-    for (i = 0; i < s->w; i++) {
-        const double *b = s->iir[ch].ab[0];
-        const double *a = s->iir[ch].ab[1];
-        double w = i * M_PI / (s->w - 1);
     double realz, realp;
     double imagz, imagp;
-        double real, imag, div;
+    double real, imag;
+    double div;
 
-        if (s->format == 0) {
+    if (format == 0) {
         realz = 0., realp = 0.;
         imagz = 0., imagp = 0.;
-            for (x = 0; x < s->iir[ch].nb_ab[1]; x++) {
+        for (int x = 0; x < nb_a; x++) {
             realz += cos(-x * w) * a[x];
             imagz += sin(-x * w) * a[x];
         }
 
-            for (x = 0; x < s->iir[ch].nb_ab[0]; x++) {
+        for (int x = 0; x < nb_b; x++) {
             realp += cos(-x * w) * b[x];
             imagp += sin(-x * w) * b[x];
         }
@@ -782,7 +765,7 @@ static void draw_response(AVFilterContext *ctx, AVFrame *out)
     } else {
         real = 1;
         imag = 0;
-            for (x = 0; x < s->iir[ch].nb_ab[1]; x++) {
+        for (int x = 0; x < nb_a; x++) {
             double ore, oim, re, im;
 
             re = cos(w) - a[2 * x];
@@ -795,7 +778,7 @@ static void draw_response(AVFilterContext *ctx, AVFrame *out)
             imag = ore * im + oim * re;
         }
 
-            for (x = 0; x < s->iir[ch].nb_ab[0]; x++) {
+        for (int x = 0; x < nb_b; x++) {
             double ore, oim, re, im;
 
             re = cos(w) - b[2 * x];
@@ -810,6 +793,38 @@ static void draw_response(AVFilterContext *ctx, AVFrame *out)
         }
     }
 
+    *r = real;
+    *i = imag;
+}
+
+static void draw_response(AVFilterContext *ctx, AVFrame *out)
+{
+    AudioIIRContext *s = ctx->priv;
+    float *mag, *phase, *delay, min = FLT_MAX, max = FLT_MIN;
+    float min_delay = FLT_MAX, max_delay = FLT_MIN;
+    int prev_ymag = -1, prev_yphase = -1, prev_ydelay = -1;
+    char text[32];
+    int ch, i;
+
+    memset(out->data[0], 0, s->h * out->linesize[0]);
+
+    phase = av_malloc_array(s->w, sizeof(*phase));
+    mag = av_malloc_array(s->w, sizeof(*mag));
+    delay = av_malloc_array(s->w, sizeof(*delay));
+    if (!mag || !phase || !delay)
+        goto end;
+
+    ch = av_clip(s->ir_channel, 0, s->channels - 1);
+    for (i = 0; i < s->w; i++) {
+        const double *b = s->iir[ch].ab[0];
+        const double *a = s->iir[ch].ab[1];
+        const int nb_b = s->iir[ch].nb_ab[0];
+        const int nb_a = s->iir[ch].nb_ab[1];
+        double w = i * M_PI / (s->w - 1);
+        double real, imag;
+
+        get_response(ch, s->format, w, b, a, nb_b, nb_a, &real, &imag);
+
         mag[i] = s->iir[ch].g * hypot(real, imag);
         phase[i] = atan2(imag, real);
         min = fminf(min, mag[i]);