celp_math: rename ff_log2 to ff_log2_q15

This name is more descriptive as the function returns a fixed-point
value with 15 fraction bits.
Signed-off-by: Mans Rullgard <mans@mansr.com>

libavcodec/acelp_pitch_delay.c

@@ -86,7 +86,7 @@ void ff_acelp_update_past_gain(
     if(erasure)
         quant_energy[0] = FFMAX(avg_gain >> log2_ma_pred_order, -10240) - 4096; // -10 and -4 in (5.10)
     else
-        quant_energy[0] = (6165 * ((ff_log2(gain_corr_factor) >> 2) - (13 << 13))) >> 13;
+        quant_energy[0] = (6165 * ((ff_log2_q15(gain_corr_factor) >> 2) - (13 << 13))) >> 13;
 }
 
 int16_t ff_acelp_decode_gain_code(

libavcodec/celp_math.c

@@ -67,7 +67,7 @@ static const uint16_t tab_log2[33] =
   26457,  27294,  28116,  28924,  29719,  30500,  31269,  32025,  32769,
 };
 
-int ff_log2(uint32_t value)
+int ff_log2_q15(uint32_t value)
 {
     uint8_t  power_int;
     uint8_t  frac_x0;

libavcodec/celp_math.h

@@ -40,7 +40,7 @@ int ff_exp2(uint16_t power);
  *
  * @return value of (1<<15) * log2(value)
  */
-int ff_log2(uint32_t value);
+int ff_log2_q15(uint32_t value);
 
 /**
  * Shift value left or right depending on sign of offset parameter.