hpw422移植新的sdk

2026-07-03 18:08:25 +08:00
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+/******************************************************************************
+ *
+ *  Copyright (C) 2014 The Android Open Source Project
+ *  Copyright 2003 - 2004 Open Interface North America, Inc. All rights reserved.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at:
+ *
+ *  http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ ******************************************************************************/
+
+/**********************************************************************************
+  $Revision: #1 $
+***********************************************************************************/
+
+/**
+ @file
+
+ Dequantizer for SBC decoder; reconstructs quantized representation of subband samples.
+
+ @ingroup codec_internal
+ */
+
+/**
+@addtogroup codec_internal
+@{
+*/
+
+/**
+ This function is a fixed-point approximation of a modification of the following
+ dequantization operation defined in the spec, as inferred from section 12.6.4:
+
+ @code
+ dequant = 2^(scale_factor+1) * ((raw * 2.0 + 1.0) / ((2^bits) - 1) - 1)
+
+ 2 <= bits <= 16
+ 0 <= raw < (2^bits)-1   (the -1 is because quantized values with all 1's are forbidden)
+
+ -65535 < dequant < 65535
+ @endcode
+
+ The code below computes the dequantized value divided by a scaling constant
+ equal to about 1.38. This constant is chosen to ensure that the entry in the
+ dequant_long_scaled table for 16 bits is as accurate as possible, since it has
+ the least relative precision available to it due to its small magnitude.
+
+ This routine outputs in Q16.15 format.
+
+ The helper array dequant_long is defined as follows:
+
+ @code
+ dequant_long_long[bits] = round(2^31 * 1/((2^bits - 1) / 1.38...)  for 2 <= bits <= 16
+ @endcode
+
+
+ Additionally, the table entries have the following property:
+
+ @code
+ dequant_long_scaled[bits] <= 2^31 / ((2^bits - 1))  for 2 <= bits <= 16
+ @endcode
+
+ Therefore
+
+ @code
+ d = 2 * raw + 1              1 <= d <= 2^bits - 2
+
+ d' = d * dequant_long[bits]
+
+                  d * dequant_long_scaled[bits] <= (2^bits - 2) * (2^31 / (2^bits - 1))
+                  d * dequant_long_scaled[bits] <= 2^31 * (2^bits - 2)/(2^bits - 1) < 2^31
+ @endcode
+
+ Therefore, d' doesn't overflow a signed 32-bit value.
+
+ @code
+
+ d' =~ 2^31 * (raw * 2.0 + 1.0) / (2^bits - 1) / 1.38...
+
+ result = d' - 2^31/1.38... =~ 2^31 * ((raw * 2.0 + 1.0) / (2^bits - 1) - 1) / 1.38...
+
+ result is therefore a scaled approximation to dequant. It remains only to
+ turn 2^31 into 2^(scale_factor+1). Since we're aiming for Q16.15 format,
+ this is achieved by shifting right by (15-scale_factor):
+
+  (2^31 * x) >> (15-scale_factor) =~ 2^(31-15+scale_factor) * x = 2^15 * 2^(1+scale_factor) * x
+ @endcode
+
+ */
+
+#include <oi_codec_sbc_private.h>
+
+#ifndef SBC_DEQUANT_LONG_SCALED_OFFSET
+#define SBC_DEQUANT_LONG_SCALED_OFFSET 1555931970
+#endif
+
+#ifndef SBC_DEQUANT_LONG_UNSCALED_OFFSET
+#define SBC_DEQUANT_LONG_UNSCALED_OFFSET 2147483648
+#endif
+
+#ifndef SBC_DEQUANT_SCALING_FACTOR
+#define SBC_DEQUANT_SCALING_FACTOR 1.38019122262781f
+#endif
+
+extern const OI_UINT32 dequant_long_scaled[17];
+extern const OI_UINT32 dequant_long_unscaled[17];
+
+/** Scales x by y bits to the right, adding a rounding factor.
+ */
+#ifndef SCALE
+#define SCALE(x, y) (((x) + (1 <<((y)-1))) >> (y))
+#endif
+
+#ifdef DEBUG_DEQUANTIZATION
+
+#include <math.h>
+
+INLINE float dequant_float(OI_UINT32 raw, OI_UINT scale_factor, OI_UINT bits)
+{
+    float result = (1 << (scale_factor+1)) * ((raw * 2.0f + 1.0f) / ((1 << bits) - 1.0f) - 1.0f);
+
+    result /= SBC_DEQUANT_SCALING_FACTOR;
+
+    /* Unless the encoder screwed up, all correct dequantized values should
+     * satisfy this inequality. Non-compliant encoders which generate quantized
+     * values with all 1-bits set can, theoretically, trigger this assert. This
+     * is unlikely, however, and only an issue in debug mode.
+     */
+    OI_ASSERT(fabs(result) < 32768 * 1.6);
+
+    return result;
+}
+
+#endif
+
+
+INLINE OI_INT32 OI_SBC_Dequant(OI_UINT32 raw, OI_UINT scale_factor, OI_UINT bits)
+{
+    OI_UINT32 d;
+    OI_INT32 result;
+
+    OI_ASSERT(scale_factor <= 15);
+    OI_ASSERT(bits <= 16);
+
+    if (bits <= 1) {
+        return 0;
+    }
+
+    d = (raw * 2) + 1;
+    d *= dequant_long_scaled[bits];
+    result = d - SBC_DEQUANT_LONG_SCALED_OFFSET;
+
+#ifdef DEBUG_DEQUANTIZATION
+    {
+        OI_INT32 integerized_float_result;
+        float float_result;
+
+        float_result = dequant_float(raw, scale_factor, bits);
+        integerized_float_result = (OI_INT32)floor(0.5f+float_result * (1 << 15));
+
+        /* This detects overflow */
+        OI_ASSERT(((result >= 0) && (integerized_float_result >= 0)) ||
+                  ((result <= 0) && (integerized_float_result <= 0)));
+    }
+#endif
+    return result >> (15 - scale_factor);
+}
+
+/* This version of Dequant does not incorporate the scaling factor of 1.38. It
+ * is intended for use with implementations of the filterbank which are
+ * hard-coded into a DSP. Output is Q16.4 format, so that after joint stereo
+ * processing (which leaves the most significant bit equal to the sign bit if
+ * the encoder is conformant) the result will fit a 24 bit fixed point signed
+ * value.*/
+
+INLINE OI_INT32 OI_SBC_Dequant_Unscaled(OI_UINT32 raw, OI_UINT scale_factor, OI_UINT bits);
+INLINE OI_INT32 OI_SBC_Dequant_Unscaled(OI_UINT32 raw, OI_UINT scale_factor, OI_UINT bits)
+{
+    OI_UINT32 d;
+    OI_INT32 result;
+
+    OI_ASSERT(scale_factor <= 15);
+    OI_ASSERT(bits <= 16);
+
+
+    if (bits <= 1) {
+        return 0;
+    }
+    if (bits == 16) {
+        result = (raw << 16) + raw - 0x7fff7fff;
+        return SCALE(result, 24 - scale_factor);
+    }
+
+
+    d = (raw * 2) + 1;
+    d *= dequant_long_unscaled[bits];
+    result = d - 0x80000000;
+
+    return SCALE(result, 24 - scale_factor);
+}
+
+/**
+@}
+*/