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/header.cpp
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/* header.cpp
Implementation of MPEG header class
A few layer III, MPEG-2 LSF, and seeking modifications made by
Jeff Tsay. MPEG-2 LSF is now supported.
Last modified : 06/04/97 */
/*
* @(#) header.cc 1.8, last edit: 6/15/94 16:51:44
* @(#) 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:
* - iostreams manipulator calls like "cerr << setw (2) << ..." replaced by
* "cerr.width (2); ..." due to problems with older GNU C++ releases.
* - syncword recognition slightly changed
*/
#ifndef GUI
#include <iostream.h>
#endif // GUI
#include "header.h"
const uint32 Header::frequencies[2][4] =
{{22050, 24000, 16000, 1},
{44100, 48000, 32000, 1}};
Header::Header()
{
framesize = 0;
nSlots = 0;
crc = NULL;
offset = NULL;
initial_sync = false;
}
Header::Header(const Header &h0)
{
int32 entries;
int32 i;
h_layer = h0.h_layer;
h_protection_bit = h0.h_protection_bit;
h_bitrate_index = h0.h_bitrate_index;
h_padding_bit = h0.h_padding_bit;
h_mode_extension = h0.h_mode_extension;
h_version = h0.h_version;
h_mode = h0.h_mode;
h_sample_frequency = h0.h_sample_frequency;
h_number_of_subbands = h0.h_number_of_subbands;
h_intensity_stereo_bound = h0.h_intensity_stereo_bound;
h_copyright = h0.h_copyright;
h_original = h0.h_original;
initial_sync = h0.initial_sync;
crc = h0.crc;
if (h0.offset) {
entries = sizeof(h0.offset) / sizeof(uint32);
offset = new uint32 [entries];
for (i=0; i<entries; i++)
offset[i] = h0.offset[i];
} else {
offset = NULL;
}
checksum = h0.checksum;
framesize = h0.framesize;
nSlots = h0.nSlots;
}
Header::~Header()
{
if (offset != NULL) delete [] offset;
}
Header& Header::operator = (const Header &h0)
{
int32 entries;
int32 i;
h_layer = h0.h_layer;
h_protection_bit = h0.h_protection_bit;
h_bitrate_index = h0.h_bitrate_index;
h_padding_bit = h0.h_padding_bit;
h_mode_extension = h0.h_mode_extension;
h_version = h0.h_version;
h_mode = h0.h_mode;
h_sample_frequency = h0.h_sample_frequency;
h_number_of_subbands = h0.h_number_of_subbands;
h_intensity_stereo_bound = h0.h_intensity_stereo_bound;
h_copyright = h0.h_copyright;
h_original = h0.h_original;
initial_sync = h0.initial_sync;
crc = h0.crc;
if (h0.offset) {
entries = sizeof(h0.offset) / sizeof(uint32);
if (offset != NULL)
delete [] offset;
offset = new uint32 [entries];
for (i=0; i<entries; i++)
offset[i] = h0.offset[i];
} else {
offset = NULL;
}
checksum = h0.checksum;
framesize = h0.framesize;
nSlots = h0.nSlots;
return *this;
}
bool Header::read_header(Ibitstream *stream, Crc16 **crcp)
{
uint32 headerstring, channel_bitrate;
if (!initial_sync) {
if (!stream->get_header(&headerstring, INITIAL_SYNC))
return false;
h_version = (e_version) ((headerstring >> 19) & 1);
if ((h_sample_frequency = (e_sample_frequency)
((headerstring >> 10) & 3)) == 3)
{
#ifdef WIN32GUI
MessageBox(NULL, "Unknown sample frequency in header",
"Stream not supported", MB_ICONSTOP | MB_OK);
#else
cerr << "Unknown sample frequency!" << endl;
#endif
return false;
}
stream->set_syncword(headerstring & 0xFFF80CC0);
initial_sync = true;
} else {
if (!stream->get_header(&headerstring, STRICT_SYNC))
return false;
} // initial_sync
/* if ((h_layer = (headerstring >> 17) & 3) == 0)
{
cerr << "unknown layer identifier found!\n";
exit (1);
}
h_layer = 4 - h_layer; // now 1 means Layer I and 3 means Layer III */
h_layer = 4 - (headerstring >> 17) & 3;
h_protection_bit = (headerstring >> 16) & 1;
/* if ((h_bitrate_index = (headerstring >> 12) & 0xF) == 15)
{
cerr << "unknown bitrate index found!\n";
exit (1);
} */
/* if (!h_bitrate_index)
{
cerr << "free format not yet implemented!\n";
exit (1);
} */
h_bitrate_index = (headerstring >> 12) & 0xF;
h_padding_bit = (headerstring >> 9) & 1;
h_mode = (e_mode)((headerstring >> 6) & 3);
/* if (h_layer == 2)
// testing validity of mode and bitrate:
if ((((h_bitrate_index >= 1 && h_bitrate_index <= 3) || h_bitrate_index == 5) &&
h_mode != single_channel) ||
(h_bitrate_index >= 11 && h_mode == single_channel))
{
cerr << "illegal combination of mode and bitrate in a layer II stream:\n"
" mode: " << mode_string ()
<< "\n bitrate: " << bitrate_string () << '\n';
exit (1);
} */
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; // should never be used
h_copyright = (bool) ((headerstring >> 3) & 1);
h_original = (bool) ((headerstring >> 2) & 1);
// calculate number of subbands:
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
calculate_framesize();
// read framedata:
if (stream->read_frame(framesize) == false)
return false;
if (!h_protection_bit)
{
// frame contains a crc checksum
checksum = (uint16) stream->get_bits(16);
if (!crc)
crc = new Crc16;
crc->add_bits(headerstring, 16);
*crcp = crc;
}
else
*crcp = NULL;
#ifdef SEEK_STOP
if (h_sample_frequency == fourtyfour_point_one) {
if (!offset) {
uint32 max = max_number_of_frames(stream);
offset = new uint32[max];
for(uint32 i=0; i<max; i++)
offset[i] = 0;
}
{
int32 cf = stream->current_frame();
int32 lf = stream->last_frame();
if ((cf > 0) && (cf == lf)) {
offset[cf] = offset[cf-1] + h_padding_bit;
} else {
offset[0] = h_padding_bit;
}
}
}
#endif // SEEK_STOP
return true;
}
uint32 Header::calculate_framesize()
// calculates framesize in bytes excluding header size
{
static const int32 bitrates[2][3][16] = {
{{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}}
};
if (h_layer == 1) {
framesize = (12 * bitrates[h_version][0][h_bitrate_index]) /
frequencies[h_version][h_sample_frequency];
if (h_padding_bit) framesize++;
framesize <<= 2; // one slot is 4 bytes long
nSlots = 0;
} else {
framesize = (144 * bitrates[h_version][h_layer - 1][h_bitrate_index]) /
frequencies[h_version][h_sample_frequency];
if (h_version == MPEG2_LSF)
framesize >>= 1;
if (h_padding_bit) framesize++;
// Layer III slots
if (h_layer == 3) {
if (h_version == MPEG1) {
nSlots = framesize - ((h_mode == single_channel) ? 17 : 32) // side info size
- (h_protection_bit ? 0 : 2) // CRC size
- 4; // header size
} else { // MPEG-2 LSF
nSlots = framesize - ((h_mode == single_channel) ? 9 : 17) // side info size
- (h_protection_bit ? 0 : 2) // CRC size
- 4; // header size
}
} else {
nSlots = 0;
}
}
framesize -= 4; // subtract header size
return framesize;
}
const char *Header::layer_string() const
{
switch (h_layer)
{
case 1:
return "I";
case 2:
return "II";
case 3:
return "III";
}
return NULL; // dummy
}
const char *Header::bitrate_string() const
{
static const char *bitrate_str[2][3][16] = {
{{"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"}}
};
return bitrate_str[h_version][h_layer - 1][h_bitrate_index];
}
const char *Header::sample_frequency_string() const
{
switch (h_sample_frequency)
{
case thirtytwo:
if (h_version == MPEG1)
return "32 kHz";
else
return "16 kHz";
case fourtyfour_point_one:
if (h_version == MPEG1)
return "44.1 kHz";
else
return "22.05 kHz";
case fourtyeight:
if (h_version == MPEG1)
return "48 kHz";
else
return "24 kHz";
}
return(NULL); // dummy
}
const char *Header::mode_string() const
{
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 NULL; // dummy
}
const char *Header::version_string() const
{
switch (h_version)
{
case MPEG1:
return "MPEG-1";
case MPEG2_LSF:
return "MPEG-2 LSF";
}
return(NULL);
}
#ifdef SEEK_STOP
// Stream searching routines
bool Header::stream_seek(Ibitstream *stream, uint32 seek_pos)
{
return((h_sample_frequency == fourtyfour_point_one) ?
stream->seek_pad(seek_pos, framesize - h_padding_bit,
this, offset) :
stream->seek(seek_pos, framesize));
}
#endif
uint32 Header::max_number_of_frames(Ibitstream *stream) const
// Returns the maximum number of frames in the stream
{
return(stream->file_size() / (framesize + 4 - h_padding_bit));
}
uint32 Header::min_number_of_frames(Ibitstream *stream) const
// Returns the minimum number of frames in the stream
{
return(stream->file_size() / (framesize + 5 - h_padding_bit));
}
real Header::ms_per_frame() const
{
static real ms_per_frame_array[3][3] = {{8.707483f, 8.0f, 12.0f},
{26.12245f, 24.0f, 36.0f},
{26.12245f, 24.0f, 36.0f}};
return ms_per_frame_array[h_layer-1][h_sample_frequency];
}
real Header::total_ms(Ibitstream *stream) const
{
return(max_number_of_frames(stream) * ms_per_frame());
}