diff --git a/libavcodec/internal.h b/libavcodec/internal.h
index 445b45ad91..afcf00d013 100644
--- a/libavcodec/internal.h
+++ b/libavcodec/internal.h
@@ -241,6 +241,25 @@ static av_always_inline int64_t ff_samples_to_time_base(AVCodecContext *avctx,
                         avctx->time_base);
 }
 
+/**
+ * 2^(x) for integer x
+ * @return correctly rounded float
+ */
+static av_always_inline float ff_exp2fi(int x) {
+    /* Normal range */
+    if (-126 <= x && x <= 128)
+        return av_int2float(x+127 << 23);
+    /* Too large */
+    else if (x > 128)
+        return INFINITY;
+    /* Subnormal numbers */
+    else if (x > -150)
+        return av_int2float(1 << (x+149));
+    /* Negligibly small */
+    else
+        return 0;
+}
+
 /**
  * Get a buffer for a frame. This is a wrapper around
  * AVCodecContext.get_buffer() and should be used instead calling get_buffer()
diff --git a/libavcodec/jpeg2000.c b/libavcodec/jpeg2000.c
index afd0966103..b5b2dbf220 100644
--- a/libavcodec/jpeg2000.c
+++ b/libavcodec/jpeg2000.c
@@ -31,6 +31,7 @@
 #include "libavutil/imgutils.h"
 #include "libavutil/mem.h"
 #include "avcodec.h"
+#include "internal.h"
 #include "jpeg2000.h"
 
 #define SHL(a, n) ((n) >= 0 ? (a) << (n) : (a) >> -(n))
@@ -192,21 +193,6 @@ void ff_jpeg2000_set_significance(Jpeg2000T1Context *t1, int x, int y,
 
 // static const uint8_t lut_gain[2][4] = { { 0, 0, 0, 0 }, { 0, 1, 1, 2 } }; (unused)
 
-static inline float exp2fi(int x) {
-    /* Normal range */
-    if (-126 <= x && x <= 128)
-        return av_int2float(x+127 << 23);
-    /* Too large */
-    else if (x > 128)
-        return INFINITY;
-    /* Subnormal numbers */
-    else if (x > -150)
-        return av_int2float(1 << (x+149));
-    /* Negligibly small */
-    else
-        return 0;
-}
-
 static void init_band_stepsize(AVCodecContext *avctx,
                                Jpeg2000Band *band,
                                Jpeg2000CodingStyle *codsty,
@@ -236,7 +222,7 @@ static void init_band_stepsize(AVCodecContext *avctx,
          * R_b = R_I + log2 (gain_b )
          * see ISO/IEC 15444-1:2002 E.1.1 eqn. E-3 and E-4 */
         gain            = cbps;
-        band->f_stepsize  = exp2fi(gain - qntsty->expn[gbandno]);
+        band->f_stepsize  = ff_exp2fi(gain - qntsty->expn[gbandno]);
         band->f_stepsize *= qntsty->mant[gbandno] / 2048.0 + 1.0;
         break;
     default: