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Initial commit.

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Jim Gray
2013-04-04 14:32:05 -07:00
parent ba5c81da32
commit d71d53e8ec
2180 changed files with 1393544 additions and 1 deletions
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code/mp3code/mhead.c Normal file
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/*____________________________________________________________________________
FreeAmp - The Free MP3 Player
MP3 Decoder originally Copyright (C) 1995-1997 Xing Technology
Corp. http://www.xingtech.com
Portions Copyright (C) 1998-1999 EMusic.com
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.
$Id: mhead.c,v 1.7 1999/10/19 07:13:09 elrod Exp $
____________________________________________________________________________*/
/*------------ mhead.c ----------------------------------------------
mpeg audio
extract info from mpeg header
portable version (adapted from c:\eco\mhead.c
add Layer III
mods 6/18/97 re mux restart, 32 bit ints
mod 5/7/98 parse mpeg 2.5
---------------------------------------------------------------------*/
#include <stdlib.h>
#include <stdio.h>
#include <float.h>
#include <math.h>
#include "mhead.h" /* mpeg header structure */
static const int mp_br_table[2][16] =
{{0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0},
{0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 0}};
static const int mp_sr20_table[2][4] =
{{441, 480, 320, -999}, {882, 960, 640, -999}};
static const int mp_br_tableL1[2][16] =
{{0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0},/* mpeg2 */
{0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448, 0}};
static const int mp_br_tableL3[2][16] =
{{0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0}, /* mpeg 2 */
{0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 0}};
static int find_sync(unsigned char *buf, int n);
static int sync_scan(unsigned char *buf, int n, int i0);
static int sync_test(unsigned char *buf, int n, int isync, int padbytes);
/*--------------------------------------------------------------*/
int head_info(unsigned char *buf, unsigned int n, MPEG_HEAD * h)
{
int framebytes;
int mpeg25_flag;
if (n > 10000)
n = 10000; /* limit scan for free format */
h->sync = 0;
//if ((buf[0] == 0xFF) && ((buf[1] & 0xF0) == 0xF0))
if ((buf[0] == 0xFF) && ((buf[0+1] & 0xF0) == 0xF0))
{
mpeg25_flag = 0; // mpeg 1 & 2
}
else if ((buf[0] == 0xFF) && ((buf[0+1] & 0xF0) == 0xE0))
{
mpeg25_flag = 1; // mpeg 2.5
}
else
return 0; // sync fail
h->sync = 1;
if (mpeg25_flag)
h->sync = 2; //low bit clear signals mpeg25 (as in 0xFFE)
h->id = (buf[0+1] & 0x08) >> 3;
h->option = (buf[0+1] & 0x06) >> 1;
h->prot = (buf[0+1] & 0x01);
h->br_index = (buf[0+2] & 0xf0) >> 4;
h->sr_index = (buf[0+2] & 0x0c) >> 2;
h->pad = (buf[0+2] & 0x02) >> 1;
h->private_bit = (buf[0+2] & 0x01);
h->mode = (buf[0+3] & 0xc0) >> 6;
h->mode_ext = (buf[0+3] & 0x30) >> 4;
h->cr = (buf[0+3] & 0x08) >> 3;
h->original = (buf[0+3] & 0x04) >> 2;
h->emphasis = (buf[0+3] & 0x03);
// if( mpeg25_flag ) {
// if( h->sr_index == 2 ) return 0; // fail 8khz
//}
/* compute framebytes for Layer I, II, III */
if (h->option < 1)
return 0;
if (h->option > 3)
return 0;
framebytes = 0;
if (h->br_index > 0)
{
if (h->option == 3)
{ /* layer I */
framebytes =
240 * mp_br_tableL1[h->id][h->br_index]
/ mp_sr20_table[h->id][h->sr_index];
framebytes = 4 * framebytes;
}
else if (h->option == 2)
{ /* layer II */
framebytes =
2880 * mp_br_table[h->id][h->br_index]
/ mp_sr20_table[h->id][h->sr_index];
}
else if (h->option == 1)
{ /* layer III */
if (h->id)
{ // mpeg1
framebytes =
2880 * mp_br_tableL3[h->id][h->br_index]
/ mp_sr20_table[h->id][h->sr_index];
}
else
{ // mpeg2
if (mpeg25_flag)
{ // mpeg2.2
framebytes =
2880 * mp_br_tableL3[h->id][h->br_index]
/ mp_sr20_table[h->id][h->sr_index];
}
else
{
framebytes =
1440 * mp_br_tableL3[h->id][h->br_index]
/ mp_sr20_table[h->id][h->sr_index];
}
}
}
}
else
framebytes = find_sync(buf, n); /* free format */
return framebytes;
}
int head_info3(unsigned char *buf, unsigned int n, MPEG_HEAD *h, int *br, unsigned int *searchForward) {
unsigned int pBuf = 0;
// jdw insertion...
while ((pBuf < n) && !((buf[pBuf] == 0xFF) &&
((buf[pBuf+1] & 0xF0) == 0xF0 || (buf[pBuf+1] & 0xF0) == 0xE0)))
{
pBuf++;
}
if (pBuf == n) return 0;
*searchForward = pBuf;
return head_info2(&(buf[pBuf]),n,h,br);
}
/*--------------------------------------------------------------*/
int head_info2(unsigned char *buf, unsigned int n, MPEG_HEAD * h, int *br)
{
int framebytes;
/*--- return br (in bits/sec) in addition to frame bytes ---*/
*br = 0;
/*-- assume fail --*/
framebytes = head_info(buf, n, h);
if (framebytes == 0)
return 0;
switch (h->option)
{
case 1: /* layer III */
{
if (h->br_index > 0)
*br = 1000 * mp_br_tableL3[h->id][h->br_index];
else
{
if (h->id) // mpeg1
*br = 1000 * framebytes * mp_sr20_table[h->id][h->sr_index] / (144 * 20);
else
{ // mpeg2
if ((h->sync & 1) == 0) // flags mpeg25
*br = 500 * framebytes * mp_sr20_table[h->id][h->sr_index] / (72 * 20);
else
*br = 1000 * framebytes * mp_sr20_table[h->id][h->sr_index] / (72 * 20);
}
}
}
break;
case 2: /* layer II */
{
if (h->br_index > 0)
*br = 1000 * mp_br_table[h->id][h->br_index];
else
*br = 1000 * framebytes * mp_sr20_table[h->id][h->sr_index] / (144 * 20);
}
break;
case 3: /* layer I */
{
if (h->br_index > 0)
*br = 1000 * mp_br_tableL1[h->id][h->br_index];
else
*br = 1000 * framebytes * mp_sr20_table[h->id][h->sr_index] / (48 * 20);
}
break;
default:
return 0; // fuck knows what this is, but it ain't one of ours...
}
return framebytes;
}
/*--------------------------------------------------------------*/
static int compare(unsigned char *buf, unsigned char *buf2)
{
if (buf[0] != buf2[0])
return 0;
if (buf[1] != buf2[1])
return 0;
return 1;
}
/*----------------------------------------------------------*/
/*-- does not scan for initial sync, initial sync assumed --*/
static int find_sync(unsigned char *buf, int n)
{
int i0, isync, nmatch, pad;
int padbytes, option;
/* mod 4/12/95 i0 change from 72, allows as low as 8kbits for mpeg1 */
i0 = 24;
padbytes = 1;
option = (buf[1] & 0x06) >> 1;
if (option == 3)
{
padbytes = 4;
i0 = 24; /* for shorter layer I frames */
}
pad = (buf[2] & 0x02) >> 1;
n -= 3; /* need 3 bytes of header */
while (i0 < 2000)
{
isync = sync_scan(buf, n, i0);
i0 = isync + 1;
isync -= pad;
if (isync <= 0)
return 0;
nmatch = sync_test(buf, n, isync, padbytes);
if (nmatch > 0)
return isync;
}
return 0;
}
/*------------------------------------------------------*/
/*---- scan for next sync, assume start is valid -------*/
/*---- return number bytes to next sync ----------------*/
static int sync_scan(unsigned char *buf, int n, int i0)
{
int i;
for (i = i0; i < n; i++)
if (compare(buf, buf + i))
return i;
return 0;
}
/*------------------------------------------------------*/
/*- test consecutative syncs, input isync without pad --*/
static int sync_test(unsigned char *buf, int n, int isync, int padbytes)
{
int i, nmatch, pad;
nmatch = 0;
for (i = 0;;)
{
pad = padbytes * ((buf[i + 2] & 0x02) >> 1);
i += (pad + isync);
if (i > n)
break;
if (!compare(buf, buf + i))
return -nmatch;
nmatch++;
}
return nmatch;
}