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diff --git a/lib/rbcodec/codecs/libpcm/ima_adpcm_common.c b/lib/rbcodec/codecs/libpcm/ima_adpcm_common.c
new file mode 100644
index 0000000000..724cce31b0
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+++ b/lib/rbcodec/codecs/libpcm/ima_adpcm_common.c
@@ -0,0 +1,171 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2010 Yoshihisa Uchida
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+#include "codeclib.h"
+#include "pcm_common.h"
+#include "ima_adpcm_common.h"
+
+/*
+ * Functions for IMA ADPCM and IMA ADPCM series format
+ *
+ * References
+ * [1] The IMA Digital Audio Focus and Technical Working Groups,
+ *     Recommended Practices for Enhancing Digital Audio Compatibility
+ *     in Multimedia Systems Revision 3.00, 1992
+ * [2] Microsoft Corporation, New Multimedia Data Types and Data Techniques,
+ *     Revision:3.0, 1994
+ * [3] ffmpeg source code, libavcodec/adpcm.c
+ */
+
+/* step table */
+static const uint16_t step_table[89] ICONST_ATTR = {
+    7, 8, 9, 10, 11, 12, 13, 14,
+    16, 17, 19, 21, 23, 25, 28, 31,
+    34, 37, 41, 45, 50, 55, 60, 66,
+    73, 80, 88, 97, 107, 118, 130, 143,
+    157, 173, 190, 209, 230, 253, 279, 307,
+    337, 371, 408, 449, 494, 544, 598, 658,
+    724, 796, 876, 963, 1060, 1166, 1282, 1411,
+    1552, 1707, 1878, 2066, 2272, 2499, 2749, 3024,
+    3327, 3660, 4026, 4428, 4871, 5358, 5894, 6484,
+    7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
+    15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794,
+    32767
+};
+
+/* step index tables */
+static const int index_tables[4][16] ICONST_ATTR = {
+    /* adpcm data size is 2 */
+    { -1, 2 },
+    /* adpcm data size is 3 */
+    { -1, -1, 1, 2 },
+    /* adpcm data size is 4 */
+    { -1, -1, -1, -1, 2, 4, 6, 8 },
+    /* adpcm data size is 5 */
+    { -1, -1, -1, -1, -1, -1, -1, -1, 1, 2, 4, 6, 8, 10, 13, 16 },
+};
+
+static int32_t pcmdata[2];
+static int8_t indices[2];
+
+static int adpcm_data_size;
+static uint8_t step_mask;
+static uint8_t step_sign_mask;
+static int8_t step_shift;
+static const int *use_index_table;
+
+/*
+ * Before first decoding, this function must be executed.
+ *
+ * params
+ *     bit: adpcm data size (2 <= bit <= 5).
+ *     index_table: step index table
+ *                  if index_table is null, then step index table
+ *                  is used index_tables[bit-2].
+ */
+void init_ima_adpcm_decoder(int bit, const int *index_table)
+{
+    adpcm_data_size = bit;
+    step_sign_mask = 1 << (adpcm_data_size - 1);
+    step_mask = step_sign_mask - 1;
+    step_shift = adpcm_data_size - 2;
+    if (index_table)
+        use_index_table = index_table;
+    else
+        use_index_table = index_tables[adpcm_data_size - 2];
+}
+
+/*
+ * When starting decoding for each block, this function must be executed.
+ *
+ * params
+ *     channels: channel count
+ *     init_pcmdata: array of init pcmdata
+ *     init_index:   array of init step indexes
+ */
+void set_decode_parameters(int channels, int32_t *init_pcmdata, int8_t *init_index)
+{
+    int ch;
+
+    for (ch = 0; ch < channels; ch++)
+    {
+        pcmdata[ch] = init_pcmdata[ch];
+        indices[ch] = init_index[ch];
+    }
+}
+
+/*
+ * convert ADPCM to PCM for any adpcm data size.
+ *
+ * If adpcm_data_size is 4, then you use create_pcmdata_size4()
+ * in place of this functon.
+ */
+int16_t create_pcmdata(int ch, uint8_t nibble)
+{
+    int check_bit = 1 << step_shift;
+    int32_t delta = 0;
+    int16_t step = step_table[indices[ch]];
+
+    do {
+        if (nibble & check_bit)
+            delta += step;
+        step >>= 1;
+        check_bit >>= 1;
+    } while (check_bit);
+    delta += step;
+
+    if (nibble & step_sign_mask)
+        pcmdata[ch] -= delta;
+    else
+        pcmdata[ch] += delta;
+
+    indices[ch] += use_index_table[nibble & step_mask];
+    CLIP(indices[ch], 0, 88);
+
+    CLIP(pcmdata[ch], -32768, 32767);
+
+    return (int16_t)pcmdata[ch];
+}
+
+/*
+ * convert ADPCM to PCM when adpcm data size is 4.
+ */
+int16_t create_pcmdata_size4(int ch, uint8_t nibble)
+{
+    int32_t delta;
+    int16_t step = step_table[indices[ch]];
+
+    delta = (step >> 3);
+    if (nibble & 4) delta += step;
+    if (nibble & 2) delta += (step >> 1);
+    if (nibble & 1) delta += (step >> 2);
+
+    if (nibble & 0x08)
+        pcmdata[ch] -= delta;
+    else
+        pcmdata[ch] += delta;
+
+    indices[ch] += use_index_table[nibble & 0x07];
+    CLIP(indices[ch], 0, 88);
+
+    CLIP(pcmdata[ch], -32768, 32767);
+
+    return (int16_t)pcmdata[ch];
+}