Fixed-point implementation of ff_cos, ff_log2, ff_exp2.

Also implemented routine for calculating sum(a[i] * a[i-offset]>>shift)

Originally committed as revision 12974 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 73 insertions, 0 deletions

diff --git a/libavcodec/acelp_math.h b/libavcodec/acelp_math.h
new file mode 100644
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+++ b/libavcodec/acelp_math.h
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+/*
+ * Various fixed-point math operations
+ *
+ * Copyright (c) 2008 Vladimir Voroshilov
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef FFMPEG_ACELP_MATH_H
+#define FFMPEG_ACELP_MATH_H
+
+/**
+ * \brief fixed-point implementation of cosine in [0; PI) domain
+ * \param arg fixed-point cosine argument, 0 <= arg < 0x4000
+ *
+ * \return value of (1<<15) * cos(arg * PI / (1<<14)), -0x8000 <= result <= 0x7fff
+ */
+int16_t ff_cos(uint16_t arg);
+
+/**
+ * \brief fixed-point implementation of exp2(x) in [0; 1] domain
+ * \param power argument to exp2, 0 <= power <= 0x7fff
+ *
+ * \return value of (1<<20) * exp2(power / (1<<15))
+ *         0x8000c <= result <= 0xfffea
+ */
+int ff_exp2(uint16_t power);
+
+/**
+ * \brief Calculates log2(x)
+ * \param value function argument, 0 < value <= 7fff ffff
+ *
+ * \return value of (1<<15) * log2(value)
+ */
+int ff_log2(uint32_t value);
+
+/**
+ * \brief Calculates sum of array elements multiplications
+ * \param speech array with input data
+ * \param length number elements to proceed
+ * \param offset offset for calculation sum of s[i]*s[i+offset]
+ * \param shift right shift by this value will be done before multiplication
+ *
+ * \return sum of multiplications
+ *
+ * \note array must be at least length+offset long!
+ */
+static int sum_of_squares(const int16_t* speech, int length, int offset, int shift)
+{
+    const int16_t* speech_end;
+    int sum = 0;
+
+    for(speech_end=speech+length; speech<speech_end; speech++)
+       sum += (speech[0] * speech[offset]) >> shift;
+
+    return sum;
+}
+
+#endif // FFMPEG_ACELP_MATH_H