[FFmpeg-cvslog] swr: add triangular dither support

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michaelni at gmx.at> | Tue Apr 10 21:10:14 2012 +0200| [b1ef4dc406e8a0bd9acea40d880aa4e74412075b] | committer: Michael Niedermayer

swr: add triangular dither support

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=b1ef4dc406e8a0bd9acea40d880aa4e74412075b
---

 libswresample/dither.c     |    5 +++++
 libswresample/swresample.c |    1 +
 libswresample/swresample.h |    1 +
 3 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/libswresample/dither.c b/libswresample/dither.c
index 4e39cce..663e200 100644
--- a/libswresample/dither.c
+++ b/libswresample/dither.c
@@ -40,6 +40,11 @@ void swri_get_dither(void *dst, int len, unsigned seed, enum AVSampleFormat out_
 
         switch(method){
             case SWR_DITHER_RECTANGULAR: v= ((double)seed) / UINT_MAX - 0.5; break;
+            case SWR_DITHER_TRIANGULAR :
+                v = ((double)seed) / UINT_MAX;
+                seed = seed*1664525 + 1013904223;
+                v-= ((double)seed) / UINT_MAX;
+                break;
             default: av_assert0(0);
         }
 
diff --git a/libswresample/swresample.c b/libswresample/swresample.c
index 8b06061..58096b3 100644
--- a/libswresample/swresample.c
+++ b/libswresample/swresample.c
@@ -55,6 +55,7 @@ static const AVOption options[]={
 {"res", "force resampling", 0, AV_OPT_TYPE_CONST, {.dbl=SWR_FLAG_RESAMPLE}, INT_MIN, INT_MAX, 0, "flags"},
 {"dither", "dither method"      , OFFSET(dither_method), AV_OPT_TYPE_INT, {.dbl=0}, 0, SWR_DITHER_NB-1, 0, "dither_method"},
 {"rectangular", "rectangular dither", 0, AV_OPT_TYPE_CONST, {.dbl=SWR_DITHER_RECTANGULAR}, INT_MIN, INT_MAX, 0, "dither_method"},
+{"triangular" , "triangular dither" , 0, AV_OPT_TYPE_CONST, {.dbl=SWR_DITHER_TRIANGULAR }, INT_MIN, INT_MAX, 0, "dither_method"},
 
 {0}
 };
diff --git a/libswresample/swresample.h b/libswresample/swresample.h
index 1f87617..9bd5b67 100644
--- a/libswresample/swresample.h
+++ b/libswresample/swresample.h
@@ -48,6 +48,7 @@
 enum SwrDitherType {
     SWR_DITHER_NONE = 0,
     SWR_DITHER_RECTANGULAR,
+    SWR_DITHER_TRIANGULAR,
     SWR_DITHER_NB,              ///< not part of API/ABI
 };