145 lines
3.7 KiB
C++
145 lines
3.7 KiB
C++
/*
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* Project 25 IMBE Encoder/Decoder Fixed-Point implementation
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* Developed by Pavel Yazev E-mail: pyazev@gmail.com
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* Version 1.0 (c) Copyright 2009
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*
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* This is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3, or (at your option)
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* any later version.
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*
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* The software is distributed in the hope that it will be useful, but
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* WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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* See the GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this; see the file COPYING. If not, write to the Free
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* Software Foundation, Inc., 51 Franklin Street, Boston, MA
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* 02110-1301, USA.
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*/
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#include "typedef.h"
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#include "basic_op.h"
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#include "qnt_sub.h"
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//-----------------------------------------------------------------------------
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// PURPOSE:
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// Dequantize by quantizer step size
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//
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//
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// INPUT:
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// qval - quantized value
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// step_size - step size used to quantize in unsigned Q0.16 format
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// bit_num - the number of bits
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//
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// OUTPUT:
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// None
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//
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// RETURN:
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// Quantized Value in signed (bit_num).16 format
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//
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//-----------------------------------------------------------------------------
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Word32 deqnt_by_step(Word16 qval, UWord16 step_size, Word16 bit_num)
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{
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Word32 res;
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if(bit_num == 0)
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return (Word32)0;
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res = (Word32)step_size * (qval - (1 << (bit_num - 1)));
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res = L_add(res, ((Word32)step_size * CNST_0_5_Q0_16) >> 16);
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return res;
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}
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//-----------------------------------------------------------------------------
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// PURPOSE:
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// Quantize by quantizer step size
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//
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//
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// INPUT:
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// val - value to be quantized in Q5.10 format
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// step_size - step size used to quantize in unsigned Q0.16 format
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// bit_num - the number of bits
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//
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// OUTPUT:
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// None
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//
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// RETURN:
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// Quantized Value in integer
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//
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//-----------------------------------------------------------------------------
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Word16 qnt_by_step(Word16 val, UWord16 step_size, Word16 bit_num)
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{
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Word16 index, min_val, max_val;
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Word16 q_index, shift, tmp;
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shift = norm_s(step_size);
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tmp = div_s(0x4000, shl(step_size, shift)); // Remark: To get result in Qxx.16 format it is necessary left shift tmp by (shift + 3)
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q_index = shr_r(mult(val, tmp), sub(9, shift)); // q_index here is rounded to the nearest integer
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max_val = 1 << (bit_num - 1);
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min_val = negate(max_val);
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if(q_index < min_val)
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index = 0;
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else if(q_index >= max_val)
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index = (1 << bit_num) - 1;
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else
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index = max_val + q_index;
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return index;
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}
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//-----------------------------------------------------------------------------
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// PURPOSE:
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// Quantize by table
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//
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//
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// INPUT:
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// val - value to be quantized
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// q_tbl - pointer to table
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// q_tbl_size - size of table
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//
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// OUTPUT:
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// None
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//
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// RETURN:
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// Quantized Value in integer
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//
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//-----------------------------------------------------------------------------
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Word16 tbl_quant(Word16 val, Word16 *q_tbl, Word16 q_tbl_size)
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{
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Word16 min_index, max_index, index;
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min_index = 0;
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max_index = q_tbl_size - 1;
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if(val >= q_tbl[max_index])
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return max_index;
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if(val <= q_tbl[min_index])
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return min_index;
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while(max_index - min_index != 1)
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{
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index = min_index + ((max_index - min_index) >> 1);
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if(q_tbl[index] > val)
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max_index = index;
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else
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min_index = index;
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}
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if(q_tbl[max_index] - val <= val - q_tbl[min_index])
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return max_index;
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else
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return min_index;
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}
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