[FFmpeg-cvslog] avcodec/jpeg2000dec: Add 5/ 3 de-quantization special case for the lossless case

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michaelni at gmx.at> | Wed Jun 24 17:05:42 2015 +0200| [05ef6324d11017420a087150f2addbb18cdb9ad3] | committer: Michael Niedermayer

avcodec/jpeg2000dec: Add 5/3 de-quantization special case for the lossless case

This avoids a multiplication and 64bits

Signed-off-by: Michael Niedermayer <michaelni at gmx.at>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=05ef6324d11017420a087150f2addbb18cdb9ad3
---

 libavcodec/jpeg2000dec.c |   10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/libavcodec/jpeg2000dec.c b/libavcodec/jpeg2000dec.c
index be78660..11f4cd6 100644
--- a/libavcodec/jpeg2000dec.c
+++ b/libavcodec/jpeg2000dec.c
@@ -1436,8 +1436,14 @@ static void dequantization_int(int x, int y, Jpeg2000Cblk *cblk,
     for (j = 0; j < (cblk->coord[1][1] - cblk->coord[1][0]); ++j) {
         int32_t *datap = &comp->i_data[(comp->coord[0][1] - comp->coord[0][0]) * (y + j) + x];
         int *src = t1->data[j];
-        for (i = 0; i < w; ++i)
-            datap[i] = (src[i] * (int64_t)band->i_stepsize) / 32768;
+        if (band->i_stepsize == 16384) {
+            for (i = 0; i < w; ++i)
+                datap[i] = src[i] / 2;
+        } else {
+            // This should be VERY uncommon
+            for (i = 0; i < w; ++i)
+                datap[i] = (src[i] * (int64_t)band->i_stepsize) / 32768;
+        }
     }
 }