diff options
Diffstat (limited to 'libavcodec/jpeg2000.c')
| -rw-r--r-- | libavcodec/jpeg2000.c | 17 |
1 files changed, 16 insertions, 1 deletions
diff --git a/libavcodec/jpeg2000.c b/libavcodec/jpeg2000.c index c98840971f..afd0966103 100644 --- a/libavcodec/jpeg2000.c +++ b/libavcodec/jpeg2000.c @@ -192,6 +192,21 @@ void ff_jpeg2000_set_significance(Jpeg2000T1Context *t1, int x, int y, // static const uint8_t lut_gain[2][4] = { { 0, 0, 0, 0 }, { 0, 1, 1, 2 } }; (unused) +static inline float exp2fi(int x) { + /* Normal range */ + if (-126 <= x && x <= 128) + return av_int2float(x+127 << 23); + /* Too large */ + else if (x > 128) + return INFINITY; + /* Subnormal numbers */ + else if (x > -150) + return av_int2float(1 << (x+149)); + /* Negligibly small */ + else + return 0; +} + static void init_band_stepsize(AVCodecContext *avctx, Jpeg2000Band *band, Jpeg2000CodingStyle *codsty, @@ -221,7 +236,7 @@ static void init_band_stepsize(AVCodecContext *avctx, * R_b = R_I + log2 (gain_b ) * see ISO/IEC 15444-1:2002 E.1.1 eqn. E-3 and E-4 */ gain = cbps; - band->f_stepsize = pow(2.0, gain - qntsty->expn[gbandno]); + band->f_stepsize = exp2fi(gain - qntsty->expn[gbandno]); band->f_stepsize *= qntsty->mant[gbandno] / 2048.0 + 1.0; break; default: |