www.pudn.com > jlayermp3midlet.rar > Header.java
/**
*-----------------------------------------------------------------------
* 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.jlme.decoder;
import java.io.IOException;
/**
* Description of the Class
*@author micah
*@created December 8,2001
*/
public final class Header {
public final static int[] [] frequencies =
{{22050,24000,16000,1},
{44100,48000,32000,1}};
/** Constant for LayerI version */
public final static int LayerI = 1;
/** Constant for LayerII version */
public final static int LayerII = 2;
/** Constant for LayerIII version */
public final static int LayerIII = 3;
/** Constant for MPEG-1 version */
public final static int MPEG1 = 1;
/** Description of the Field */
public final static int STEREO = 0;
/** Description of the Field */
public final static int JOINT_STEREO = 1;
/** Description of the Field */
public final static int DUAL_CHANNEL = 2;
/** Description of the Field */
public final static int SINGLE_CHANNEL = 3;
/** Description of the Field */
public final static int FOURTYFOUR_POINT_ONE = 0;
/** Description of the Field */
public final static int FOURTYEIGHT = 1;
/** Description of the Field */
public final static int THIRTYTWO = 2;
/** Description of the Field */
public final static int bitrates[] [] [] = {
{{0
/*
* free format
*/
,32000,48000,56000,64000,80000,96000,
112000,128000,144000,160000,176000,192000,224000,256000,0},
{0
/*
* free format
*/
,8000,16000,24000,32000,40000,48000,
56000,64000,80000,96000,112000,128000,144000,160000,0},
{0
/*
* free format
*/
,8000,16000,24000,32000,40000,48000,
56000,64000,80000,96000,112000,128000,144000,160000,0}},
{{0
/*
* free format
*/
,32000,64000,96000,128000,160000,192000,
224000,256000,288000,320000,352000,384000,416000,448000,0},
{0
/*
* free format
*/
,32000,48000,56000,64000,80000,96000,
112000,128000,160000,192000,224000,256000,320000,384000,0},
{0
/*
* free format
*/
,32000,40000,48000,56000,64000,80000,
96000,112000,128000,160000,192000,224000,256000,320000,0}}
};
/** Description of the Field */
public final static String bitrate_str[] [] [] = {
{{"free format","32 kbit/s","48 kbit/s","56 kbit/s","64 kbit/s",
"80 kbit/s","96 kbit/s","112 kbit/s","128 kbit/s","144 kbit/s",
"160 kbit/s","176 kbit/s","192 kbit/s","224 kbit/s","256 kbit/s",
"forbidden"},
{"free format","8 kbit/s","16 kbit/s","24 kbit/s","32 kbit/s",
"40 kbit/s","48 kbit/s","56 kbit/s","64 kbit/s","80 kbit/s",
"96 kbit/s","112 kbit/s","128 kbit/s","144 kbit/s","160 kbit/s",
"forbidden"},
{"free format","8 kbit/s","16 kbit/s","24 kbit/s","32 kbit/s",
"40 kbit/s","48 kbit/s","56 kbit/s","64 kbit/s","80 kbit/s",
"96 kbit/s","112 kbit/s","128 kbit/s","144 kbit/s","160 kbit/s",
"forbidden"}},
{{"free format","32 kbit/s","64 kbit/s","96 kbit/s","128 kbit/s",
"160 kbit/s","192 kbit/s","224 kbit/s","256 kbit/s","288 kbit/s",
"320 kbit/s","352 kbit/s","384 kbit/s","416 kbit/s","448 kbit/s",
"forbidden"},
{"free format","32 kbit/s","48 kbit/s","56 kbit/s","64 kbit/s",
"80 kbit/s","96 kbit/s","112 kbit/s","128 kbit/s","160 kbit/s",
"192 kbit/s","224 kbit/s","256 kbit/s","320 kbit/s","384 kbit/s",
"forbidden"},
{"free format","32 kbit/s","40 kbit/s","48 kbit/s","56 kbit/s",
"64 kbit/s","80 kbit/s","96 kbit/s","112 kbit/s","128 kbit/s",
"160 kbit/s","192 kbit/s","224 kbit/s","256 kbit/s","320 kbit/s",
"forbidden"}}
};
public static int framesize;
public static int nSlots;
private static int h_layer,h_protection_bit,h_bitrate_index,h_padding_bit,h_mode_extension;
private static int h_version;
private static int h_mode;
private static int h_sample_frequency;
private static int h_number_of_subbands,h_intensity_stereo_bound;
private static byte syncmode = BitStream.INITIAL_SYNC;
public int version() {
return h_version;
}
public int layer() {
return h_layer;
}
public int bitrate_index() {
return h_bitrate_index;
}
public int sample_frequency() {
return h_sample_frequency;
}
public int frequency() {
return frequencies[h_version] [h_sample_frequency];
}
public int mode() {
return h_mode;
}
public boolean padding() {
return (h_padding_bit != 0);
}
public int slots() {
return nSlots;
}
public int mode_extension() {
return h_mode_extension;
}
public String layer_string() {
if (h_layer==1) return "III";
switch (h_layer) {
case LayerI:
return "LayerI";
case LayerII :
return "LayerII";
case LayerIII:
return "LayerIII";
}
return "Unknown";
}
public String bitrate_string() {
return bitrate_str[h_version] [h_layer - 1] [h_bitrate_index];
}
public String sample_frequency_string() {
switch (h_sample_frequency) {
case THIRTYTWO:
return "32 kHz";
case FOURTYFOUR_POINT_ONE:
return "44.1 kHz";
case FOURTYEIGHT:
return "48 kHz";
}
return "not set";
}
public String mode_string() {
switch (h_mode) {
case STEREO:
return "Stereo";
case JOINT_STEREO:
return "Joint stereo";
case DUAL_CHANNEL:
return "Dual channel";
case SINGLE_CHANNEL:
return "Single channel";
}
return "not set";
}
public int number_of_subbands() {
return h_number_of_subbands;
}
public int intensity_stereo_bound() {
return h_intensity_stereo_bound;
}
final void read_header(BitStream stream) throws IOException {
int headerstring;
int channel_bitrate;
boolean sync = false;
do {
headerstring = stream.syncHeader(syncmode);
if (syncmode == BitStream.INITIAL_SYNC) {
h_version = ((headerstring >>> 19) & 1);
if ((h_sample_frequency = ((headerstring >>> 10) & 3)) == 3) {
return;
}
}
h_layer = 4 - (headerstring >>> 17) & 3;
// E.B Fix.
//h_protection_bit = 0;
h_protection_bit = (headerstring >>> 16) & 1;
// End.
h_bitrate_index = (headerstring >>> 12) & 0xF;
h_padding_bit = (headerstring >>> 9) & 1;
h_mode = ((headerstring >>> 6) & 3);
h_mode_extension = (headerstring >>> 4) & 3;
if (h_mode == JOINT_STEREO) {
h_intensity_stereo_bound = (h_mode_extension << 2) + 4;
} else {
h_intensity_stereo_bound = 0;
}
if (h_layer == 1) {
h_number_of_subbands = 32;
} else {
channel_bitrate = h_bitrate_index;
// calculate bitrate per channel:
if (h_mode != SINGLE_CHANNEL) {
if (channel_bitrate == 4) {
channel_bitrate = 1;
} else {
channel_bitrate -= 4;
}
}
if ((channel_bitrate == 1) || (channel_bitrate == 2)) {
if (h_sample_frequency == THIRTYTWO) {
h_number_of_subbands = 12;
} else {
h_number_of_subbands = 8;
}
} else if ((h_sample_frequency == FOURTYEIGHT) || ((channel_bitrate >= 3) && (channel_bitrate <= 5))) {
h_number_of_subbands = 27;
} else {
h_number_of_subbands = 30;
}
}
if (h_intensity_stereo_bound > h_number_of_subbands) {
h_intensity_stereo_bound = h_number_of_subbands;
}
// calculate framesize and nSlots
calFrameSize();
// read framedata:
stream.read_frame_data(framesize);
if (stream.isSyncCurrentPosition(syncmode)) {
if (syncmode == BitStream.INITIAL_SYNC) {
syncmode = BitStream.STRICT_SYNC;
stream.set_syncword(headerstring & 0xFFF80CC0);
}
sync = true;
}
else {
stream.unreadFrame();
}
} while (!sync);
stream.parse_frame();
// E.B Fix
if (h_protection_bit == 0)
{
// frame contains a crc checksum
short checksum = (short) stream.readbits(16);
}
// End
}
/* only supports mpeg1 frames; stripped out mpeg2 checking */
private final void calFrameSize() {
framesize = (144 * bitrates[h_version] [h_layer - 1] [h_bitrate_index]) / frequencies[h_version] [h_sample_frequency];
if(h_padding_bit != 0)
framesize++;
if(h_version == MPEG1)
// E.B Fix
nSlots = framesize - ((h_mode == SINGLE_CHANNEL) ? 17 : 32) - ((h_protection_bit!=0) ? 0 : 2) - 4;
//nSlots = framesize - ((h_mode == SINGLE_CHANNEL) ? 17 : 32) - 4;
// End.
else{
System.out.println("sorry,doesn't support mpeg2 frames - only LayerIII is supported");
System.exit(1);
}
framesize -= 4;
}
}