Re: [FFmpeg-devel] [PATCH 3/4] avcodec/jpeg2000: Simplify exp2fi for numbers used here
mån 2024-02-19 klockan 15:14 +0100 skrev Andreas Rheinhardt: > Tomas Härdin: > > lör 2024-02-17 klockan 21:05 +0100 skrev Andreas Rheinhardt: > > > 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. > > > > Any measurable improvement in decode speed? > > > > I don't think it is measurable; my aim was to move ff_exp2fi() out of > internal.h (where it does not belong). Ah. Well, fewer branches is almost always good so, looks good to me. Maybe pal has an opinion? /Tomas ___ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-devel] [PATCH 3/4] avcodec/jpeg2000: Simplify exp2fi for numbers used here
Tomas Härdin: > lör 2024-02-17 klockan 21:05 +0100 skrev Andreas Rheinhardt: >> 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. > > Any measurable improvement in decode speed? > I don't think it is measurable; my aim was to move ff_exp2fi() out of internal.h (where it does not belong). - Andreas ___ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
Re: [FFmpeg-devel] [PATCH 3/4] avcodec/jpeg2000: Simplify exp2fi for numbers used here
lör 2024-02-17 klockan 21:05 +0100 skrev Andreas Rheinhardt: > 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. Any measurable improvement in decode speed? /Tomas ___ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
[FFmpeg-devel] [PATCH 3/4] 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.
Signed-off-by: Andreas Rheinhardt
---
libavcodec/jpeg2000.c | 18 ++
1 file changed, 14 insertions(+), 4 deletions(-)
diff --git a/libavcodec/jpeg2000.c b/libavcodec/jpeg2000.c
index 0aa984bc53..d6ffb02319 100644
--- a/libavcodec/jpeg2000.c
+++ b/libavcodec/jpeg2000.c
@@ -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;
--
2.34.1
___
ffmpeg-devel mailing list
ffmpeg-devel@ffmpeg.org
https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
To unsubscribe, visit link above, or email
ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
