diff --git a/libavcodec/iirfilter.c b/libavcodec/iirfilter.c
index 727a370444..cefe35ab6e 100644
--- a/libavcodec/iirfilter.c
+++ b/libavcodec/iirfilter.c
@@ -277,20 +277,6 @@ av_cold struct FFIIRFilterState *ff_iir_filter_init_state(int order)
     }                                                                       \
 }
 
-void ff_iir_filter(const struct FFIIRFilterCoeffs *c,
-                   struct FFIIRFilterState *s, int size,
-                   const int16_t *src, ptrdiff_t sstep,
-                   int16_t *dst, ptrdiff_t dstep)
-{
-    if (c->order == 2) {
-        FILTER_O2(int16_t, S16)
-    } else if (c->order == 4) {
-        FILTER_BW_O4(int16_t, S16)
-    } else {
-        FILTER_DIRECT_FORM_II(int16_t, S16)
-    }
-}
-
 /**
  * Perform IIR filtering on floating-point input samples.
  *
diff --git a/libavcodec/iirfilter.h b/libavcodec/iirfilter.h
index d6b8fe2782..8ab8ae68c6 100644
--- a/libavcodec/iirfilter.h
+++ b/libavcodec/iirfilter.h
@@ -28,7 +28,6 @@
 #define AVCODEC_IIRFILTER_H
 
 #include <stddef.h>
-#include <stdint.h>
 
 struct FFIIRFilterCoeffs;
 struct FFIIRFilterState;
@@ -114,18 +113,4 @@ void ff_iir_filter_free_coeffsp(struct FFIIRFilterCoeffs **coeffs);
  */
 void ff_iir_filter_free_statep(struct FFIIRFilterState **state);
 
-/**
- * Perform IIR filtering on signed 16-bit input samples.
- *
- * @param coeffs pointer to filter coefficients
- * @param state  pointer to filter state
- * @param size   input length
- * @param src    source samples
- * @param sstep  source stride
- * @param dst    filtered samples (destination may be the same as input)
- * @param dstep  destination stride
- */
-void ff_iir_filter(const struct FFIIRFilterCoeffs *coeffs, struct FFIIRFilterState *state,
-                   int size, const int16_t *src, ptrdiff_t sstep, int16_t *dst, ptrdiff_t dstep);
-
 #endif /* AVCODEC_IIRFILTER_H */
diff --git a/libavcodec/tests/iirfilter.c b/libavcodec/tests/iirfilter.c
index 60cc6fc43d..e03e842b85 100644
--- a/libavcodec/tests/iirfilter.c
+++ b/libavcodec/tests/iirfilter.c
@@ -23,10 +23,25 @@
 #include "libavutil/libm.h"
 
 #include "libavcodec/iirfilter.h"
+#include "libavcodec/iirfilter.c"
 
 #define FILT_ORDER 4
 #define SIZE 1024
 
+static void iir_filter_int16(const struct FFIIRFilterCoeffs *c,
+                             struct FFIIRFilterState *s, int size,
+                             const int16_t *src, ptrdiff_t sstep,
+                             int16_t *dst, ptrdiff_t dstep)
+{
+    if (c->order == 2) {
+        FILTER_O2(int16_t, S16)
+    } else if (c->order == 4) {
+        FILTER_BW_O4(int16_t, S16)
+    } else {
+        FILTER_DIRECT_FORM_II(int16_t, S16)
+    }
+}
+
 int main(void)
 {
     struct FFIIRFilterCoeffs *fcoeffs = NULL;
@@ -43,7 +58,7 @@ int main(void)
     for (i = 0; i < SIZE; i++)
         x[i] = lrint(0.75 * INT16_MAX * sin(0.5 * M_PI * i * i / SIZE));
 
-    ff_iir_filter(fcoeffs, fstate, SIZE, x, 1, y, 1);
+    iir_filter_int16(fcoeffs, fstate, SIZE, x, 1, y, 1);
 
     for (i = 0; i < SIZE; i++)
         printf("%6d %6d\n", x[i], y[i]);