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exp() and log() are faster than pow() and log10() for dB conversion

--- a/libcelt/quant_bands.c

+++ b/libcelt/quant_bands.c

@@ -71,7 +71,8 @@

 static inline celt_ener_t dB2Amp(celt_ener_t dB)

 {

    celt_ener_t amp;

-   amp = pow(10, .05*dB)-.3;

+   /*amp = pow(10, .05*dB)-.3;*/

+   amp = exp(0.115129f*dB)-.3f;

    if (amp < 0)

       amp = 0;

    return amp;

@@ -78,7 +79,8 @@

 }

 static inline celt_word16_t amp2dB(celt_ener_t amp)

 {

-   return 20*log10(.3+amp);

+   /*return 20*log10(.3+amp);*/

+   return 8.68589f*log(.3f+amp);

 }

 #endif