diff --git a/libavcodec/acelp_vectors.c b/libavcodec/acelp_vectors.c
index b193d08865..b83c270190 100644
--- a/libavcodec/acelp_vectors.c
+++ b/libavcodec/acelp_vectors.c
@@ -127,6 +127,26 @@ void ff_acelp_fc_pulse_per_track(
     fc_v[tab2[pulse_indexes]] += (pulse_signs & 1) ? 8191 : -8192;
 }
 
+void ff_decode_10_pulses_35bits(const int16_t *fixed_index,
+                                AMRFixed *fixed_sparse,
+                                const uint8_t *gray_decode,
+                                int half_pulse_count, int bits)
+{
+    int i;
+    int mask = (1 << bits) - 1;
+
+    fixed_sparse->n = 2 * half_pulse_count;
+    for (i = 0; i < half_pulse_count; i++) {
+        const int pos1   = gray_decode[fixed_index[2*i+1] & mask] + i;
+        const int pos2   = gray_decode[fixed_index[2*i  ] & mask] + i;
+        const float sign = (fixed_index[2*i+1] & (1 << bits)) ? -1.0 : 1.0;
+        fixed_sparse->x[2*i+1] = pos1;
+        fixed_sparse->x[2*i  ] = pos2;
+        fixed_sparse->y[2*i+1] = sign;
+        fixed_sparse->y[2*i  ] = pos2 < pos1 ? -sign : sign;
+    }
+}
+
 void ff_acelp_weighted_vector_sum(
         int16_t* out,
         const int16_t *in_a,
@@ -188,3 +208,37 @@ void ff_scale_vector_to_given_sum_of_squares(float *out, const float *in,
     for (i = 0; i < n; i++)
         out[i] = in[i] * scalefactor;
 }
+
+void ff_set_fixed_vector(float *out, const AMRFixed *in, float scale, int size)
+{
+    int i;
+
+    for (i=0; i < in->n; i++) {
+        int x   = in->x[i];
+        float y = in->y[i] * scale;
+        out[x] += y;
+
+        x += in->pitch_lag;
+        while (x < size) {
+            y *= in->pitch_fac;
+            out[x] += y;
+            x += in->pitch_lag;
+        }
+    }
+}
+
+void ff_clear_fixed_vector(float *out, const AMRFixed *in, int size)
+{
+    int i;
+
+    for (i=0; i < in->n; i++) {
+        int x  = in->x[i];
+        out[x] = 0.0;
+
+        x += in->pitch_lag;
+        while (x < size) {
+            out[x] = 0.0;
+            x += in->pitch_lag;
+        }
+    }
+}
diff --git a/libavcodec/acelp_vectors.h b/libavcodec/acelp_vectors.h
index a711160d4c..10cbc08946 100644
--- a/libavcodec/acelp_vectors.h
+++ b/libavcodec/acelp_vectors.h
@@ -25,6 +25,15 @@
 
 #include <stdint.h>
 
+/** Sparse representation for the algebraic codebook (fixed) vector */
+typedef struct {
+    int      n;
+    int      x[10];
+    float    y[10];
+    int      pitch_lag;
+    float    pitch_fac;
+} AMRFixed;
+
 /**
  * Track|Pulse|        Positions
  * -------------------------------------------------------------------------
@@ -125,6 +134,24 @@ void ff_acelp_fc_pulse_per_track(
         int pulse_count,
         int bits);
 
+/**
+ * Decode the algebraic codebook index to pulse positions and signs and
+ * construct the algebraic codebook vector for MODE_12k2.
+ *
+ * @note: The positions and signs are explicitly coded in MODE_12k2.
+ *
+ * @param fixed_index          positions of the ten pulses
+ * @param fixed_sparse         pointer to the algebraic codebook vector
+ * @param gray_decode          gray decoding table
+ * @param half_pulse_count     number of couples of pulses
+ * @param bits                 length of one pulse index in bits
+ */
+void ff_decode_10_pulses_35bits(const int16_t *fixed_index,
+                                AMRFixed *fixed_sparse,
+                                const uint8_t *gray_decode,
+                                int half_pulse_count, int bits);
+
+
 /**
  * weighted sum of two vectors with rounding.
  * @param out [out] result of addition
@@ -194,4 +221,23 @@ void ff_adaptative_gain_control(float *buf_out, float speech_energ,
 void ff_scale_vector_to_given_sum_of_squares(float *out, const float *in,
                                              float sum_of_squares, const int n);
 
+/**
+ * Add fixed vector to an array from a sparse representation
+ *
+ * @param out fixed vector with pitch sharpening
+ * @param in sparse fixed vector
+ * @param scale number to multiply the fixed vector by
+ * @param size the output vector size
+ */
+void ff_set_fixed_vector(float *out, const AMRFixed *in, float scale, int size);
+
+/**
+ * Clear array values set by set_fixed_vector
+ *
+ * @param out fixed vector to be cleared
+ * @param in sparse fixed vector
+ * @param size the output vector size
+ */
+void ff_clear_fixed_vector(float *out, const AMRFixed *in, int size);
+
 #endif /* AVCODEC_ACELP_VECTORS_H */