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EnigmA Amiga Run 1995 October
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EnigmA AMIGA RUN 01 (1995)(G.R. Edizioni)(IT)[!][issue 1995-10][Aminet 7].iso
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header.cc
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C/C++ Source or Header
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1994-06-23
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7KB
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250 lines
/*
* @(#) 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
*/
#include <sys/types.h>
#include <unistd.h>
#include <iostream.h>
#include <iomanip.h>
#include <stdlib.h>
#include "header.h"
const uint32 Header::frequencies[3] = { 44100, 48000, 32000 };
bool Header::read_header (Ibitstream *stream, Crc16 **crcp)
{
uint32 headerstring;
if (!stream->get_header (&headerstring))
return False;
if ((headerstring & 0xFFF80000) != 0xFFF80000)
{
cerr << "invalid syncword 0x";
cerr.width (8);
cerr.fill ('0');
cerr << hex << headerstring
<< " found at fileoffset " << dec
<< lseek (stream->filedescriptor (), 0, SEEK_CUR) - 4 << '\n';
return False;
}
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
if (h_layer == 3)
{
cerr << "Sorry, Layer III not implemented!\n";
exit (1);
}
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);
}
if ((h_sample_frequency = (e_sample_frequency)((headerstring >> 10) & 3)) == 3)
{
cerr << "unknown sample frequency!\n";
exit (1);
}
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 = (headerstring >> 3) & 1;
h_original = (headerstring >> 2) & 1;
// calculate number of subbands:
if (h_layer == 1)
h_number_of_subbands = 32;
else
{
uint32 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;
// read framedata:
if (!stream->read_frame (calculate_framesize ()))
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 = (Crc16 *)0;
return True;
}
uint32 Header::calculate_framesize ()
/* calculates framesize in bytes excluding header size */
{
static const int32 bitrates_layer_1[15] = {
0 /*free format*/, 32000, 64000, 96000, 128000, 160000, 192000,
224000, 256000, 288000, 320000, 352000, 384000, 416000, 448000 };
static const int32 bitrates_layer_2[15] = {
0 /*free format*/, 32000, 48000, 56000, 64000, 80000, 96000,
112000, 128000, 160000, 192000, 224000, 256000, 320000, 384000 };
static const samplefrequencies[3] = { 44100, 48000, 32000 };
uint32 framesize;
if (h_layer == 1)
{
framesize = (12 * bitrates_layer_1[h_bitrate_index]) / samplefrequencies[h_sample_frequency];
if (h_sample_frequency == fourtyfour_point_one && h_padding_bit)
++framesize;
framesize <<= 2; // one slot is 4 bytes long
}
else
{
framesize = (144 * bitrates_layer_2[h_bitrate_index]) / samplefrequencies[h_sample_frequency];
if (h_sample_frequency == fourtyfour_point_one && h_padding_bit)
++framesize;
}
return framesize - 4; // subtract header size
}
const char *Header::layer_string (void)
{
switch (h_layer)
{
case 1:
return "I";
case 2:
return "II";
case 3:
return "III (not implemented!)";
}
return NULL; // dummy
}
const char *Header::bitrate_string (void)
{
static const char *layer1_bitrates[16] = {
"free format", "32 kbis/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"
};
static const char *layer2_bitrates[16] = {
"free format", "32 kbis/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"
};
if (h_layer == 1)
return layer1_bitrates[h_bitrate_index];
else
return layer2_bitrates[h_bitrate_index];
}
const char *Header::sample_frequency_string (void)
{
switch (h_sample_frequency)
{
case thirtytwo:
return "32 kHz";
case fourtyfour_point_one:
return "44.1 kHz";
case fourtyeight:
return "48 kHz";
}
return NULL; // dummy
}
const char *Header::mode_string (void)
{
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
}