@@ -47,29 +47,25 @@ typedef struct FFIIRFilterState{

 /// maximum supported filter order

 #define MAXORDER 30

-av_cold struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs(void *avc,

-                                                enum IIRFilterType filt_type,

-                                                enum IIRFilterMode filt_mode,

-                                                int order, float cutoff_ratio,

-                                                float stopband, float ripple)

+static int butterworth_init_coeffs(void *avc, struct FFIIRFilterCoeffs *c,

+                                   enum IIRFilterMode filt_mode,

+                                   int order, float cutoff_ratio,

+                                   float stopband)

 {

     int i, j;

-    FFIIRFilterCoeffs *c;

     double wa;

     double p[MAXORDER + 1][2];

-    if(filt_type != FF_FILTER_TYPE_BUTTERWORTH || filt_mode != FF_FILTER_MODE_LOWPASS)

-        return NULL;

-    if(order <= 1 || (order & 1) || order > MAXORDER || cutoff_ratio >= 1.0)

-        return NULL;

-

-    FF_ALLOCZ_OR_GOTO(avc, c,     sizeof(FFIIRFilterCoeffs),

-                      init_fail);

-    FF_ALLOC_OR_GOTO (avc, c->cx, sizeof(c->cx[0]) * ((order >> 1) + 1),

-                      init_fail);

-    FF_ALLOC_OR_GOTO (avc, c->cy, sizeof(c->cy[0]) * order,

-                      init_fail);

-    c->order = order;

+    if (filt_mode != FF_FILTER_MODE_LOWPASS) {

+        av_log(avc, AV_LOG_ERROR, "Butterworth filter currently only supports "

+               "low-pass filter mode\n");

+        return -1;

+    }

+    if (order & 1) {

+        av_log(avc, AV_LOG_ERROR, "Butterworth filter currently only supports "

+               "even filter orders\n");

+        return -1;

+    }

     wa = 2 * tan(M_PI * 0.5 * cutoff_ratio);

@@ -113,6 +109,38 @@ av_cold struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs(void *avc,

     }

     c->gain /= 1 << order;

+    return 0;

+}

+

+av_cold struct FFIIRFilterCoeffs* ff_iir_filter_init_coeffs(void *avc,

+                                                enum IIRFilterType filt_type,

+                                                enum IIRFilterMode filt_mode,

+                                                int order, float cutoff_ratio,

+                                                float stopband, float ripple)

+{

+    FFIIRFilterCoeffs *c;

+

+    if (order <= 0 || order > MAXORDER || cutoff_ratio >= 1.0)

+        return NULL;

+

+    FF_ALLOCZ_OR_GOTO(avc, c,     sizeof(FFIIRFilterCoeffs),

+                      init_fail);

+    FF_ALLOC_OR_GOTO (avc, c->cx, sizeof(c->cx[0]) * ((order >> 1) + 1),

+                      init_fail);

+    FF_ALLOC_OR_GOTO (avc, c->cy, sizeof(c->cy[0]) * order,

+                      init_fail);

+    c->order = order;

+

+    if (filt_type == FF_FILTER_TYPE_BUTTERWORTH) {

+        if (butterworth_init_coeffs(avc, c, filt_mode, order, cutoff_ratio,

+            stopband)) {

+            goto init_fail;

+        }

+    } else {

+        av_log(avc, AV_LOG_ERROR, "filter type is not currently implemented\n");

+        goto init_fail;

+    }

+

     return c;

 init_fail: