swr: add dither support.

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

1 files changed, 56 insertions, 0 deletions

diff --git a/libswresample/dither.c b/libswresample/dither.c
new file mode 100644
index 0000000000..4e39cceb0d
--- /dev/null
+++ b/libswresample/dither.c
@@ -0,0 +1,56 @@
+/*
+ * Copyright (C) 2012 Michael Niedermayer (michaelni@gmx.at)
+ *
+ * This file is part of libswresample
+ *
+ * libswresample is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * libswresample is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with libswresample; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "libavutil/avassert.h"
+#include "swresample_internal.h"
+
+void swri_get_dither(void *dst, int len, unsigned seed, enum AVSampleFormat out_fmt, enum AVSampleFormat in_fmt, enum SwrDitherType method) {
+    double scale = 0;
+    int i;
+
+    if(in_fmt == AV_SAMPLE_FMT_FLT || in_fmt == AV_SAMPLE_FMT_DBL){
+        if(out_fmt == AV_SAMPLE_FMT_S32) scale = 1.0/(1L<<31);
+        if(out_fmt == AV_SAMPLE_FMT_S16) scale = 1.0/(1L<<15);
+        if(out_fmt == AV_SAMPLE_FMT_U8 ) scale = 1.0/(1L<< 7);
+    }
+    if(in_fmt == AV_SAMPLE_FMT_S32 && out_fmt == AV_SAMPLE_FMT_S16) scale = 1L<<16;
+    if(in_fmt == AV_SAMPLE_FMT_S32 && out_fmt == AV_SAMPLE_FMT_U8 ) scale = 1L<<24;
+    if(in_fmt == AV_SAMPLE_FMT_S16 && out_fmt == AV_SAMPLE_FMT_U8 ) scale = 1L<<8;
+
+    for(i=0; i<len; i++){
+        double v;
+        seed = seed* 1664525 + 1013904223;
+
+        switch(method){
+            case SWR_DITHER_RECTANGULAR: v= ((double)seed) / UINT_MAX - 0.5; break;
+            default: av_assert0(0);
+        }
+
+        v*= scale;
+
+        switch(in_fmt){
+            case AV_SAMPLE_FMT_S16: ((int16_t*)dst)[i] = v; break;
+            case AV_SAMPLE_FMT_S32: ((int32_t*)dst)[i] = v; break;
+            case AV_SAMPLE_FMT_FLT: ((float  *)dst)[i] = v; break;
+            case AV_SAMPLE_FMT_DBL: ((double *)dst)[i] = v; break;
+            default: av_assert0(0);
+        }
+    }
+}