diff --git a/libavcodec/acelp_filters.c b/libavcodec/acelp_filters.c
index 2aedbddab3..fb52d0f8c9 100644
--- a/libavcodec/acelp_filters.c
+++ b/libavcodec/acelp_filters.c
@@ -116,13 +116,14 @@ int ff_acelp_lp_synthesis_filter(
         const int16_t* in,
         int buffer_length,
         int filter_length,
-        int stop_on_overflow)
+        int stop_on_overflow,
+        int rounder)
 {
     int i,n;
 
     for(n=0; n<buffer_length; n++)
     {
-        int sum = 0x800;
+        int sum = rounder;
         for(i=1; i<filter_length; i++)
             sum -= filter_coeffs[i] * out[n-i];
 
diff --git a/libavcodec/acelp_filters.h b/libavcodec/acelp_filters.h
index 167faf72c3..a21fc88a49 100644
--- a/libavcodec/acelp_filters.h
+++ b/libavcodec/acelp_filters.h
@@ -128,6 +128,7 @@ void ff_acelp_convolve_circ(
  * \param filter_length filter length (11 for 10th order LP filter)
  * \param stop_on_overflow   1 - return immediately if overflow occurs
  *                           0 - ignore overflows
+ * \param rounder the amount to add for rounding (usually 0x800 or 0xfff)
  *
  * \return 1 if overflow occurred, 0 - otherwise
  *
@@ -142,7 +143,8 @@ int ff_acelp_lp_synthesis_filter(
         const int16_t* in,
         int buffer_length,
         int filter_length,
-        int stop_on_overflow);
+        int stop_on_overflow,
+        int rounder);
 
 /**
  * \brief Calculates coefficients of weighted A(z/weight) filter.