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avcodec/jpeg2000: Simplify exp2fi for numbers used here 

The call to ff_exp2fi() here always uses arguments in the normal
range, so that the branches in ff_exp2fi() are unnecessary.
This is so because JPEG2000 itself only supports up to
128 bits per component per pixel (we only support far less);
furthermore, expn is always 0..31 for the decoder and also
sane for the encoder, so that the difference between these
two values is always in the normal range of -126..128.

Reviewed-by: Tomas Härdin <git@haerdin.se>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt 2024-02-17 19:49:29 +01:00
parent 271d6709cf
commit 42f6dfc42e
1 changed files with 14 additions and 4 deletions
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18
libavcodec/jpeg2000.c
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@ -32,7 +32,6 @@
#include "libavutil/mem.h"
#include "libavutil/thread.h"
#include "avcodec.h"
#include "internal.h"
#include "jpeg2000.h"
#define SHL(a, n) ((n) >= 0 ? (a) << (n) : (a) >> -(n))
@ -201,6 +200,17 @@ 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)
/**
* 2^(x) for integer x in the range -126..128.
* @return correctly rounded float
*/
static av_always_inline float exp2fi(int x)
{
av_assert2(-126 <= x && x <= 128);
/* Normal range */
return av_int2float((x+127) << 23);
}
static void init_band_stepsize(AVCodecContext *avctx,
Jpeg2000Band *band,
Jpeg2000CodingStyle *codsty,
@ -230,7 +240,7 @@ 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 = ff_exp2fi(gain - qntsty->expn[gbandno]);
band->f_stepsize = exp2fi(gain - qntsty->expn[gbandno]);
band->f_stepsize *= qntsty->mant[gbandno] / 2048.0 + 1.0;
break;
default:
@ -391,7 +401,7 @@ static int init_band(AVCodecContext *avctx,
Jpeg2000CodingStyle *codsty,
Jpeg2000QuantStyle *qntsty,
int bandno, int gbandno, int reslevelno,
int cbps, int dx, int dy)
const int cbps, int dx, int dy)
{
Jpeg2000Band *band = reslevel->band + bandno;
uint8_t log2_band_prec_width, log2_band_prec_height;
@ -466,7 +476,7 @@ static int init_band(AVCodecContext *avctx,
int ff_jpeg2000_init_component(Jpeg2000Component *comp,
Jpeg2000CodingStyle *codsty,
Jpeg2000QuantStyle *qntsty,
int cbps, int dx, int dy,
const int cbps, int dx, int dy,
AVCodecContext *avctx)
{
int reslevelno, bandno, gbandno = 0, ret, i, j;