gusucode.com > VC++ mp3解压源代码-源码程序 > VC++ mp3解压源代码-源码程序/code/mp3/sublay1.cpp
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/* sublay1.cpp
Implementation of layer I subband objects */
/*
* @(#) subband_layer_1.cc 1.7, last edit: 6/15/94 16:51:49
* @(#) Copyright (C) 1993, 1994 Tobias Bading (bading@cs.tu-berlin.de)
* @(#) Berlin University of Technology
*
* 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 program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
/*
* Changes from version 1.1 to 1.2:
* - scalefactors itself instead of scalefactor indices are stored in
* SubbandLayer1... objects
* - check for small values in [-1.0E-7, 1.0E-7] removed, because the
* test itself was slower than some SynthesisFilter::input_sample() calls
* - check for illegal scalefactor index 63 removed
*/
#include "sublay1.h"
#include "scalfact.h"
#ifdef __WIN32__
#pragma warning (disable: 4305)
#endif
// factors and offsets for sample requantization:
static const real table_factor[15] = {
0.0, (1.0/2.0) * (4.0/3.0), (1.0/4.0) * (8.0/7.0), (1.0/8.0) * (16.0/15.0),
(1.0/16.0) * (32.0/31.0), (1.0/32.0) * (64.0/63.0), (1.0/64.0) * (128.0/127.0),
(1.0/128.0) * (256.0/255.0), (1.0/256.0) * (512.0/511.0),
(1.0/512.0) * (1024.0/1023.0), (1.0/1024.0) * (2048.0/2047.0),
(1.0/2048.0) * (4096.0/4095.0), (1.0/4096.0) * (8192.0/8191.0),
(1.0/8192.0) * (16384.0/16383.0), (1.0/16384.0) * (32768.0/32767.0)
};
static const real table_offset[15] = {
0.0, ((1.0/2.0)-1.0) * (4.0/3.0), ((1.0/4.0)-1.0) * (8.0/7.0), ((1.0/8.0)-1.0) * (16.0/15.0),
((1.0/16.0)-1.0) * (32.0/31.0), ((1.0/32.0)-1.0) * (64.0/63.0), ((1.0/64.0)-1.0) * (128.0/127.0),
((1.0/128.0)-1.0) * (256.0/255.0), ((1.0/256.0)-1.0) * (512.0/511.0),
((1.0/512.0)-1.0) * (1024.0/1023.0), ((1.0/1024.0)-1.0) * (2048.0/2047.0),
((1.0/2048.0)-1.0) * (4096.0/4095.0), ((1.0/4096.0)-1.0) * (8192.0/8191.0),
((1.0/8192.0)-1.0) * (16384.0/16383.0), ((1.0/16384.0)-1.0) * (32768.0/32767.0)
};
/**********************/ // used for single channel mode
/*** Standard Class ***/ // and in derived class for intensity
/**********************/ // stereo mode
SubbandLayer1::SubbandLayer1 (uint32 subbandnumber)
{
this->subbandnumber = subbandnumber;
samplenumber = 0;
}
void SubbandLayer1::read_allocation (Ibitstream *stream, Header *, Crc16 *crc)
{
if ((allocation = stream->get_bits (4)) == 15) ;
// cerr << "WARNING: stream contains an illegal allocation!\n"; // MPEG-stream is corrupted!
if (crc)
crc->add_bits (allocation, 4);
if (allocation)
{
samplelength = allocation + 1;
factor = table_factor[allocation];
offset = table_offset[allocation];
}
}
void SubbandLayer1::read_scalefactor (Ibitstream *stream, Header *)
{
if (allocation)
scalefactor = scalefactors[stream->get_bits (6)];
}
bool SubbandLayer1::read_sampledata (Ibitstream *stream)
{
if (allocation)
{
sample = real (stream->get_bits (samplelength));
}
if (++samplenumber == 12)
{
samplenumber = 0;
return true;
}
return false;
}
bool SubbandLayer1::put_next_sample (e_channels channels,
SynthesisFilter *filter1, SynthesisFilter *)
{
if (allocation && channels != right)
{
register real scaled_sample = (sample * factor + offset) * scalefactor;
filter1->input_sample (scaled_sample, subbandnumber);
}
return true;
}
/******************************/
/*** Intensity Stereo Class ***/
/******************************/
SubbandLayer1IntensityStereo::SubbandLayer1IntensityStereo (uint32 subbandnumber)
: SubbandLayer1 (subbandnumber)
{
}
void SubbandLayer1IntensityStereo::read_scalefactor (Ibitstream *stream, Header *)
{
if (allocation)
{
scalefactor = scalefactors[stream->get_bits (6)];
channel2_scalefactor = scalefactors[stream->get_bits (6)];
}
}
bool SubbandLayer1IntensityStereo::put_next_sample (e_channels channels,
SynthesisFilter *filter1, SynthesisFilter *filter2)
{
if (allocation)
{
sample = sample * factor + offset; // requantization
if (channels == both)
{
register real sample1 = sample * scalefactor,
sample2 = sample * channel2_scalefactor;
filter1->input_sample (sample1, subbandnumber);
filter2->input_sample (sample2, subbandnumber);
}
else if (channels == left)
{
register real sample1 = sample * scalefactor;
filter1->input_sample (sample1, subbandnumber);
}
else
{
register real sample2 = sample * channel2_scalefactor;
filter1->input_sample (sample2, subbandnumber);
}
}
return true;
}
/********************/
/*** Stereo Class ***/
/********************/
SubbandLayer1Stereo::SubbandLayer1Stereo (uint32 subbandnumber)
: SubbandLayer1 (subbandnumber)
{
}
void SubbandLayer1Stereo::read_allocation (Ibitstream *stream, Header *, Crc16 *crc)
{
allocation = stream->get_bits (4);
channel2_allocation = stream->get_bits (4);
if (crc)
{
crc->add_bits (allocation, 4);
crc->add_bits (channel2_allocation, 4);
}
if (allocation)
{
samplelength = allocation + 1;
factor = table_factor[allocation];
offset = table_offset[allocation];
}
if (channel2_allocation)
{
channel2_samplelength = channel2_allocation + 1;
channel2_factor = table_factor[channel2_allocation];
channel2_offset = table_offset[channel2_allocation];
}
}
void SubbandLayer1Stereo::read_scalefactor (Ibitstream *stream, Header *)
{
if (allocation)
scalefactor = scalefactors[stream->get_bits (6)];
if (channel2_allocation)
channel2_scalefactor = scalefactors[stream->get_bits (6)];
}
bool SubbandLayer1Stereo::read_sampledata (Ibitstream *stream)
{
bool returnvalue = SubbandLayer1::read_sampledata (stream);
if (channel2_allocation)
{
channel2_sample = real (stream->get_bits (channel2_samplelength));
}
return(returnvalue);
}
bool SubbandLayer1Stereo::put_next_sample (e_channels channels,
SynthesisFilter *filter1, SynthesisFilter *filter2)
{
SubbandLayer1::put_next_sample (channels, filter1, filter2);
if (channel2_allocation && channels != left)
{
register float sample2 = (channel2_sample * channel2_factor + channel2_offset) *
channel2_scalefactor;
if (channels == both)
filter2->input_sample (sample2, subbandnumber);
else
filter1->input_sample (sample2, subbandnumber);
}
return true;
}