add initial structure

1 files changed, 106 insertions, 0 deletions

diff --git a/portaudio/src/common/pa_dither.h b/portaudio/src/common/pa_dither.h
new file mode 100644
index 0000000..4f81123
--- /dev/null
+++ b/portaudio/src/common/pa_dither.h
@@ -0,0 +1,106 @@
+#ifndef PA_DITHER_H
+#define PA_DITHER_H
+/*
+ * $Id$
+ * Portable Audio I/O Library triangular dither generator
+ *
+ * Based on the Open Source API proposed by Ross Bencina
+ * Copyright (c) 1999-2002 Phil Burk, Ross Bencina
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files
+ * (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge,
+ * publish, distribute, sublicense, and/or sell copies of the Software,
+ * and to permit persons to whom the Software is furnished to do so,
+ * subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR
+ * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF
+ * CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+/*
+ * The text above constitutes the entire PortAudio license; however,
+ * the PortAudio community also makes the following non-binding requests:
+ *
+ * Any person wishing to distribute modifications to the Software is
+ * requested to send the modifications to the original developer so that
+ * they can be incorporated into the canonical version. It is also
+ * requested that these non-binding requests be included along with the
+ * license above.
+ */
+
+/** @file
+ @ingroup common_src
+
+ @brief Functions for generating dither noise
+*/
+
+#include "pa_types.h"
+
+
+#ifdef __cplusplus
+extern "C"
+{
+#endif /* __cplusplus */
+
+/* Note that the linear congruential algorithm requires 32 bit integers
+ * because it uses arithmetic overflow. So use PaUint32 instead of
+ * unsigned long so it will work on 64 bit systems.
+ */
+
+/** @brief State needed to generate a dither signal */
+typedef struct PaUtilTriangularDitherGenerator{
+    PaUint32 previous;
+    PaUint32 randSeed1;
+    PaUint32 randSeed2;
+} PaUtilTriangularDitherGenerator;
+
+
+/** @brief Initialize dither state */
+void PaUtil_InitializeTriangularDitherState( PaUtilTriangularDitherGenerator *ditherState );
+
+
+/**
+ @brief Calculate 2 LSB dither signal with a triangular distribution.
+ Ranged for adding to a 1 bit right-shifted 32 bit integer
+ prior to >>15. eg:
+<pre>
+    signed long in = *
+    signed long dither = PaUtil_Generate16BitTriangularDither( ditherState );
+    signed short out = (signed short)(((in>>1) + dither) >> 15);
+</pre>
+ @return
+ A signed 32-bit integer with a range of +32767 to -32768
+*/
+PaInt32 PaUtil_Generate16BitTriangularDither( PaUtilTriangularDitherGenerator *ditherState );
+
+
+/**
+ @brief Calculate 2 LSB dither signal with a triangular distribution.
+ Ranged for adding to a pre-scaled float.
+<pre>
+    float in = *
+    float dither = PaUtil_GenerateFloatTriangularDither( ditherState );
+    // use smaller scaler to prevent overflow when we add the dither
+    signed short out = (signed short)(in*(32766.0f) + dither );
+</pre>
+ @return
+ A float with a range of -2.0 to +1.99999.
+*/
+float PaUtil_GenerateFloatTriangularDither( PaUtilTriangularDitherGenerator *ditherState );
+
+
+
+#ifdef __cplusplus
+}
+#endif /* __cplusplus */
+#endif /* PA_DITHER_H */