rename pitch_delay_frac in ff_acelp_interpolate()

Originally committed as revision 14893 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/acelp_filters.c

@@ -47,7 +47,7 @@ void ff_acelp_interpolate(
         const int16_t* in,
         const int16_t* filter_coeffs,
         int precision,
-        int pitch_delay_frac,
+        int frac_pos,
         int filter_length,
         int length)
 {
@@ -72,10 +72,10 @@ void ff_acelp_interpolate(
                 v += R(n-i)*ff_acelp_interp_filter(t+6i)
                 v += R(n+i+1)*ff_acelp_interp_filter(6-t+6i) */
 
-            v += in[n + i] * filter_coeffs[idx + pitch_delay_frac];
+            v += in[n + i] * filter_coeffs[idx + frac_pos];
             idx += precision;
             i++;
-            v += in[n - i] * filter_coeffs[idx - pitch_delay_frac];
+            v += in[n - i] * filter_coeffs[idx - frac_pos];
         }
         out[n] = av_clip_int16(v >> 15);
     }