helper utilities to decode ima4 encoded files

10 years ago · 4b82d31b50
parent 96dc002b02
commit 4b82d31b50
1 changed files with 142 additions and 0 deletions
--- a/include/libnyquist/IMA4Util.h
+++ b/include/libnyquist/IMA4Util.h
@ -0,0 +1,142 @@
+/*
+Copyright (c) 2015, Dimitri Diakopoulos All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+
+* Redistributions in binary form must reproduce the above copyright notice,
+  this list of conditions and the following disclaimer in the documentation
+  and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/
+
+#ifndef IMA4_UTIL_H
+#define IMA4_UTIL_H
+
+#include "AudioDecoder.h"
+
+namespace nqr
+{
+
+    struct ADPCMState
+    {
+        int nBlockAlign;
+        int firstDataBlockByte;
+        int dataSize;
+        int currentByte;
+        const uint8_t * currentDatablock; // A buffer containing the current encoded datablock.
+        int predict = 0;
+        int stepIndex = 0;
+    };
+
+    static const int ima_index_table[16] =
+    {
+        -1, -1, -1, -1, 2, 4, 6, 8,
+        -1, -1, -1, -1, 2, 4, 6, 8
+    };
+
+    static inline int ima_clamp_index(int index)
+    {
+        if (index < 0) return 0;
+        else if (index > 88) return 88;
+        return index;
+    }
+    
+    static inline int16_t ima_clamp_predict(int16_t predict)
+    {
+        if (predict < -32768) return -32768;
+        else if (predict > 32767) return 32767;
+        return predict;
+    }
+    
+    static const int ima_step_table[89] =
+    {
+        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
+    };
+
+    // Decodes an IMA ADPCM nibble to a 16 bit pcm sample
+    static inline int16_t decode_nibble(uint8_t nibble, int16_t & p, int & s)
+    {
+        // Compute a delta to add to the predictor value
+        int diff = 0;
+        if (nibble & 4) diff += ima_step_table[s];
+        if (nibble & 2) diff += ima_step_table[s] >> 1;
+        if (nibble & 1) diff += ima_step_table[s] >> 2;
+        
+        diff += ima_step_table[s] >> 3;
+        
+        // Sign
+        if (nibble & 8) diff = -diff;
+        
+        // Add delta
+        p += diff;
+        
+        p = ima_clamp_predict(p);
+        s += ima_index_table[nibble];
+        s = ima_clamp_index(s);
+        
+        return p;
+    }
+    
+    void decode_ima_adpcm(ADPCMState & state, int16_t * outBuffer, uint32_t num_channels)
+    {
+        const uint8_t * data = state.currentDatablock;
+        
+        // Loop over the interleaved words
+        for (int32_t ch = 0; ch < num_channels; ch++)
+        {
+            const int byteOffset = ch * 4;
+            
+            // Get step table index and predicted value from the header word for the current channel
+            int16_t predictedSample = (data[byteOffset] | (data[byteOffset + 1] << 8));
+            int stepIndex = data[byteOffset + 2];
+            
+            // Reserved byte of the header word should be 0.
+            uint8_t reserved = data[byteOffset + 3];
+            if (reserved != 0) std::cout << "Fuck" << std::endl;
+            
+            int byteIdx = num_channels * 4 + byteOffset; //the byte index of the first data word for this channel
+            int idx = ch;
+            
+            // Decode each nibble of the current data word, containing 8 encoded samples, for the current channel
+            while (byteIdx < state.nBlockAlign)
+            {
+                for (int j = 0; j < 4; j++)
+                {
+                    outBuffer[idx] = decode_nibble(data[byteIdx] & 0xf, predictedSample, stepIndex); // low nibble
+                    idx += num_channels;
+                    outBuffer[idx] = decode_nibble(data[byteIdx] >> 4, predictedSample, stepIndex); // high nibble
+                    idx += num_channels;
+                    byteIdx++;
+                }
+                byteIdx += (num_channels - 1) << 2; // Jump to the next data word for the current channel
+            }
+
+        }
+
+    }
+
+} // end namespace nqr
+
+#endif