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MP3 decoder/player/converter library for Java™ platform.
The newest version!
/*
* 09/26/08 throw exception on subbband alloc error: Christopher G. Jennings ([email protected])
*
* 11/19/04 1.0 moved to LGPL.
*
* 12/12/99 Initial version. Adapted from javalayer.java
* and Subband*.java. [email protected]
*
* 02/28/99 Initial version : javalayer.java by E.B
*-----------------------------------------------------------------------
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU Library 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 Library General Public License for more details.
*
* You should have received a copy of the GNU Library General Public
* License along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*----------------------------------------------------------------------
*/
package javazoom.jl.decoder;
/**
* Implements decoding of MPEG Audio Layer I frames.
*/
class LayerIDecoder implements FrameDecoder
{
protected Bitstream stream;
protected Header header;
protected SynthesisFilter filter1, filter2;
protected Obuffer buffer;
protected int which_channels;
protected int mode;
protected int num_subbands;
protected Subband[] subbands;
protected Crc16 crc = null; // new Crc16[1] to enable CRC checking.
public LayerIDecoder()
{
crc = new Crc16();
}
public void create(Bitstream stream0, Header header0,
SynthesisFilter filtera, SynthesisFilter filterb,
Obuffer buffer0, int which_ch0)
{
stream = stream0;
header = header0;
filter1 = filtera;
filter2 = filterb;
buffer = buffer0;
which_channels = which_ch0;
}
public void decodeFrame() throws DecoderException
{
num_subbands = header.number_of_subbands();
subbands = new Subband[32];
mode = header.mode();
createSubbands();
readAllocation();
readScaleFactorSelection();
if ((crc != null) || header.checksum_ok())
{
readScaleFactors();
readSampleData();
}
}
protected void createSubbands()
{
int i;
if (mode == Header.SINGLE_CHANNEL)
for (i = 0; i < num_subbands; ++i)
subbands[i] = new SubbandLayer1(i);
else if (mode == Header.JOINT_STEREO)
{
for (i = 0; i < header.intensity_stereo_bound(); ++i)
subbands[i] = new SubbandLayer1Stereo(i);
for (; i < num_subbands; ++i)
subbands[i] = new SubbandLayer1IntensityStereo(i);
}
else
{
for (i = 0; i < num_subbands; ++i)
subbands[i] = new SubbandLayer1Stereo(i);
}
}
protected void readAllocation() throws DecoderException
{
// start to read audio data:
for (int i = 0; i < num_subbands; ++i)
subbands[i].read_allocation(stream, header, crc);
}
protected void readScaleFactorSelection()
{
// scale factor selection not present for layer I.
}
protected void readScaleFactors()
{
for (int i = 0; i < num_subbands; ++i)
subbands[i].read_scalefactor(stream, header);
}
protected void readSampleData()
{
boolean read_ready = false;
boolean write_ready = false;
int mode = header.mode();
int i;
do
{
for (i = 0; i < num_subbands; ++i)
read_ready = subbands[i].read_sampledata(stream);
do
{
for (i = 0; i < num_subbands; ++i)
write_ready = subbands[i].put_next_sample(which_channels,filter1, filter2);
filter1.calculate_pcm_samples(buffer);
if ((which_channels == OutputChannels.BOTH_CHANNELS) && (mode != Header.SINGLE_CHANNEL))
filter2.calculate_pcm_samples(buffer);
} while (!write_ready);
} while (!read_ready);
}
/**
* Abstract base class for subband classes of layer I and II
*/
static abstract class Subband
{
/*
* Changes from version 1.1 to 1.2:
* - array size increased by one, although a scalefactor with index 63
* is illegal (to prevent segmentation faults)
*/
// Scalefactors for layer I and II, Annex 3-B.1 in ISO/IEC DIS 11172:
public static final float scalefactors[] =
{
2.00000000000000f, 1.58740105196820f, 1.25992104989487f, 1.00000000000000f,
0.79370052598410f, 0.62996052494744f, 0.50000000000000f, 0.39685026299205f,
0.31498026247372f, 0.25000000000000f, 0.19842513149602f, 0.15749013123686f,
0.12500000000000f, 0.09921256574801f, 0.07874506561843f, 0.06250000000000f,
0.04960628287401f, 0.03937253280921f, 0.03125000000000f, 0.02480314143700f,
0.01968626640461f, 0.01562500000000f, 0.01240157071850f, 0.00984313320230f,
0.00781250000000f, 0.00620078535925f, 0.00492156660115f, 0.00390625000000f,
0.00310039267963f, 0.00246078330058f, 0.00195312500000f, 0.00155019633981f,
0.00123039165029f, 0.00097656250000f, 0.00077509816991f, 0.00061519582514f,
0.00048828125000f, 0.00038754908495f, 0.00030759791257f, 0.00024414062500f,
0.00019377454248f, 0.00015379895629f, 0.00012207031250f, 0.00009688727124f,
0.00007689947814f, 0.00006103515625f, 0.00004844363562f, 0.00003844973907f,
0.00003051757813f, 0.00002422181781f, 0.00001922486954f, 0.00001525878906f,
0.00001211090890f, 0.00000961243477f, 0.00000762939453f, 0.00000605545445f,
0.00000480621738f, 0.00000381469727f, 0.00000302772723f, 0.00000240310869f,
0.00000190734863f, 0.00000151386361f, 0.00000120155435f, 0.00000000000000f /* illegal scalefactor */
};
public abstract void read_allocation (Bitstream stream, Header header, Crc16 crc) throws DecoderException;
public abstract void read_scalefactor (Bitstream stream, Header header);
public abstract boolean read_sampledata (Bitstream stream);
public abstract boolean put_next_sample (int channels, SynthesisFilter filter1, SynthesisFilter filter2);
};
/**
* Class for layer I subbands in single channel mode.
* Used for single channel mode
* and in derived class for intensity stereo mode
*/
static class SubbandLayer1 extends Subband
{
// Factors and offsets for sample requantization
public static final float table_factor[] = {
0.0f, (1.0f/2.0f) * (4.0f/3.0f), (1.0f/4.0f) * (8.0f/7.0f), (1.0f/8.0f) * (16.0f/15.0f),
(1.0f/16.0f) * (32.0f/31.0f), (1.0f/32.0f) * (64.0f/63.0f), (1.0f/64.0f) * (128.0f/127.0f),
(1.0f/128.0f) * (256.0f/255.0f), (1.0f/256.0f) * (512.0f/511.0f),
(1.0f/512.0f) * (1024.0f/1023.0f), (1.0f/1024.0f) * (2048.0f/2047.0f),
(1.0f/2048.0f) * (4096.0f/4095.0f), (1.0f/4096.0f) * (8192.0f/8191.0f),
(1.0f/8192.0f) * (16384.0f/16383.0f), (1.0f/16384.0f) * (32768.0f/32767.0f)
};
public static final float table_offset[] = {
0.0f, ((1.0f/2.0f)-1.0f) * (4.0f/3.0f), ((1.0f/4.0f)-1.0f) * (8.0f/7.0f), ((1.0f/8.0f)-1.0f) * (16.0f/15.0f),
((1.0f/16.0f)-1.0f) * (32.0f/31.0f), ((1.0f/32.0f)-1.0f) * (64.0f/63.0f), ((1.0f/64.0f)-1.0f) * (128.0f/127.0f),
((1.0f/128.0f)-1.0f) * (256.0f/255.0f), ((1.0f/256.0f)-1.0f) * (512.0f/511.0f),
((1.0f/512.0f)-1.0f) * (1024.0f/1023.0f), ((1.0f/1024.0f)-1.0f) * (2048.0f/2047.0f),
((1.0f/2048.0f)-1.0f) * (4096.0f/4095.0f), ((1.0f/4096.0f)-1.0f) * (8192.0f/8191.0f),
((1.0f/8192.0f)-1.0f) * (16384.0f/16383.0f), ((1.0f/16384.0f)-1.0f) * (32768.0f/32767.0f)
};
protected int subbandnumber;
protected int samplenumber;
protected int allocation;
protected float scalefactor;
protected int samplelength;
protected float sample;
protected float factor, offset;
/**
* Construtor.
*/
public SubbandLayer1(int subbandnumber)
{
this.subbandnumber = subbandnumber;
samplenumber = 0;
}
/**
*
*/
public void read_allocation(Bitstream stream, Header header, Crc16 crc) throws DecoderException
{
if ((allocation = stream.get_bits (4)) == 15)
{
// CGJ: catch this condition and throw appropriate exception
throw new DecoderException(DecoderErrors.ILLEGAL_SUBBAND_ALLOCATION, null);
// cerr << "WARNING: stream contains an illegal allocation!\n";
// MPEG-stream is corrupted!
}
if (crc != null) crc.add_bits (allocation, 4);
if (allocation != 0)
{
samplelength = allocation + 1;
factor = table_factor[allocation];
offset = table_offset[allocation];
}
}
/**
*
*/
public void read_scalefactor(Bitstream stream, Header header)
{
if (allocation != 0) scalefactor = scalefactors[stream.get_bits(6)];
}
/**
*
*/
public boolean read_sampledata(Bitstream stream)
{
if (allocation != 0)
{
sample = (float) (stream.get_bits(samplelength));
}
if (++samplenumber == 12)
{
samplenumber = 0;
return true;
}
return false;
}
/**
*
*/
public boolean put_next_sample(int channels, SynthesisFilter filter1, SynthesisFilter filter2)
{
if ((allocation !=0) && (channels != OutputChannels.RIGHT_CHANNEL))
{
float scaled_sample = (sample * factor + offset) * scalefactor;
filter1.input_sample (scaled_sample, subbandnumber);
}
return true;
}
};
/**
* Class for layer I subbands in joint stereo mode.
*/
static class SubbandLayer1IntensityStereo extends SubbandLayer1
{
protected float channel2_scalefactor;
/**
* Constructor
*/
public SubbandLayer1IntensityStereo(int subbandnumber)
{
super(subbandnumber);
}
/**
*
*/
public void read_allocation(Bitstream stream, Header header, Crc16 crc) throws DecoderException
{
super.read_allocation (stream, header, crc);
}
/**
*
*/
public void read_scalefactor (Bitstream stream, Header header)
{
if (allocation != 0)
{
scalefactor = scalefactors[stream.get_bits(6)];
channel2_scalefactor = scalefactors[stream.get_bits(6)];
}
}
/**
*
*/
public boolean read_sampledata(Bitstream stream)
{
return super.read_sampledata (stream);
}
/**
*
*/
public boolean put_next_sample (int channels, SynthesisFilter filter1, SynthesisFilter filter2)
{
if (allocation !=0 )
{
sample = sample * factor + offset; // requantization
if (channels == OutputChannels.BOTH_CHANNELS)
{
float sample1 = sample * scalefactor,
sample2 = sample * channel2_scalefactor;
filter1.input_sample(sample1, subbandnumber);
filter2.input_sample(sample2, subbandnumber);
}
else if (channels == OutputChannels.LEFT_CHANNEL)
{
float sample1 = sample * scalefactor;
filter1.input_sample(sample1, subbandnumber);
}
else
{
float sample2 = sample * channel2_scalefactor;
filter1.input_sample(sample2, subbandnumber);
}
}
return true;
}
};
/**
* Class for layer I subbands in stereo mode.
*/
static class SubbandLayer1Stereo extends SubbandLayer1
{
protected int channel2_allocation;
protected float channel2_scalefactor;
protected int channel2_samplelength;
protected float channel2_sample;
protected float channel2_factor, channel2_offset;
/**
* Constructor
*/
public SubbandLayer1Stereo(int subbandnumber)
{
super(subbandnumber);
}
/**
*
*/
public void read_allocation (Bitstream stream, Header header, Crc16 crc) throws DecoderException
{
allocation = stream.get_bits(4);
channel2_allocation = stream.get_bits(4);
if (crc != null)
{
crc.add_bits (allocation, 4);
crc.add_bits (channel2_allocation, 4);
}
if (allocation != 0)
{
samplelength = allocation + 1;
factor = table_factor[allocation];
offset = table_offset[allocation];
}
if (channel2_allocation != 0)
{
channel2_samplelength = channel2_allocation + 1;
channel2_factor = table_factor[channel2_allocation];
channel2_offset = table_offset[channel2_allocation];
}
}
/**
*
*/
public void read_scalefactor(Bitstream stream, Header header)
{
if (allocation != 0) scalefactor = scalefactors[stream.get_bits(6)];
if (channel2_allocation != 0) channel2_scalefactor = scalefactors[stream.get_bits(6)];
}
/**
*
*/
public boolean read_sampledata (Bitstream stream)
{
boolean returnvalue = super.read_sampledata(stream);
if (channel2_allocation != 0)
{
channel2_sample = (float) (stream.get_bits(channel2_samplelength));
}
return(returnvalue);
}
/**
*
*/
public boolean put_next_sample(int channels, SynthesisFilter filter1, SynthesisFilter filter2)
{
super.put_next_sample (channels, filter1, filter2);
if ((channel2_allocation != 0) && (channels != OutputChannels.LEFT_CHANNEL))
{
float sample2 = (channel2_sample * channel2_factor + channel2_offset) *
channel2_scalefactor;
if (channels == OutputChannels.BOTH_CHANNELS)
filter2.input_sample (sample2, subbandnumber);
else
filter1.input_sample (sample2, subbandnumber);
}
return true;
}
};
}