mhead.cpp

著名的 helix realplayer 基于手机 symbian 系统的 播放器全套源代码

/* ***** BEGIN LICENSE BLOCK ***** 
 * Version: RCSL 1.0/RPSL 1.0 
 *  
 * Portions Copyright (c) 1995-2002 RealNetworks, Inc. All Rights Reserved. 
 *      
 * The contents of this file, and the files included with this file, are 
 * subject to the current version of the RealNetworks Public Source License 
 * Version 1.0 (the "RPSL") available at 
 * http://www.helixcommunity.org/content/rpsl unless you have licensed 
 * the file under the RealNetworks Community Source License Version 1.0 
 * (the "RCSL") available at http://www.helixcommunity.org/content/rcsl, 
 * in which case the RCSL will apply. You may also obtain the license terms 
 * directly from RealNetworks.  You may not use this file except in 
 * compliance with the RPSL or, if you have a valid RCSL with RealNetworks 
 * applicable to this file, the RCSL.  Please see the applicable RPSL or 
 * RCSL for the rights, obligations and limitations governing use of the 
 * contents of the file.  
 *  
 * This file is part of the Helix DNA Technology. RealNetworks is the 
 * developer of the Original Code and owns the copyrights in the portions 
 * it created. 
 *  
 * This file, and the files included with this file, is distributed and made 
 * available on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER 
 * EXPRESS OR IMPLIED, AND REALNETWORKS HEREBY DISCLAIMS ALL SUCH WARRANTIES, 
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, FITNESS 
 * FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. 
 * 
 * Technology Compatibility Kit Test Suite(s) Location: 
 *    http://www.helixcommunity.org/content/tck 
 * 
 * Contributor(s): 
 *  
 * ***** END LICENSE BLOCK ***** */ 

#include "hlxclib/stdlib.h"
#include "hlxclib/stdio.h"
#include "hlxclib/float.h"
#include "hlxclib/math.h"
#include "hlxclib/string.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 trustFrame)
{
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) ) {
    mpeg25_flag = 0;            // mpeg 1 & 2
}
else if( (buf[0] == 0xFF) && ((buf[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[1] & 0x08) >> 3;
h->option     = (buf[1] & 0x06) >> 1;
h->prot       = (buf[1] & 0x01);

h->br_index   = (buf[2] & 0xf0) >> 4;
h->sr_index   = (buf[2] & 0x0c) >> 2;
h->pad        = (buf[2] & 0x02) >> 1;
h->private_bit   = (buf[2] & 0x01);
h->mode       = (buf[3] & 0xc0) >> 6;
h->mode_ext   = (buf[3] & 0x30) >> 4;
h->cr         = (buf[3] & 0x08) >> 3;
h->original   = (buf[3] & 0x04) >> 2;
h->emphasis   = (buf[3] & 0x03);


//if( mpeg25_flag ) {
//    if( h->sr_index == 2 ) return 0;   // fail 8khz
//}


/* Found a clip with a bad emphasis value.  Let this slide for now */
/*if (h->emphasis == 2)
    return 0;
*/

/* do some error checking */
if (h->br_index == 0xFF ||
    h->sr_index == 3 ||
    h->option < 1 ||
    h->option > 3)
{
    memset(h, 0, sizeof(*h));
    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 */
    // If trustFrame != 0, that means we know that we only
    // have valid frames in this buffer (i.e. - we know
    // we are being called from the renderer where our
    // fileformat has already parsed out the frames).
    // Therefore, if find_sync() did not find any frames
    // and trustFrame != 0, then accept the rest of the buffer
    // as valid.
    if (framebytes == 0 && trustFrame != 0)
    {
        // Accept the rest of the buffer as a frame
        framebytes = n - h->pad;
    }
    // The spec states "The decoder is also not required to support bitrates
    // higher than 448 kbits/s, 384 kbits/sec, 320 kbits/sec in respect to Layer I,
    // II, and III when in free format mode."
    if (framebytes)
    {
        // Compute the bitrate
        int lBitrate = 0;
        if(h->option == 1)
        {
            /* layer III */
            if (h->br_index > 0)
                lBitrate = 1000 * mp_br_tableL3[h->id][h->br_index];
            else
            {
                if(h->id) // mpeg1
                    lBitrate = 1000 * framebytes * mp_sr20_table[h->id][h->sr_index]/(144*20);
                else
                {
                    // mpeg2
                    if((h->sync & 1) == 0) //  flags mpeg25
                        lBitrate = 500*framebytes*mp_sr20_table[h->id][h->sr_index]/(72*20);
                    else
                        lBitrate = 1000*framebytes*mp_sr20_table[h->id][h->sr_index]/(72*20);
                }
            }
            // Cap the bitrate
            if (lBitrate > 320000 || lBitrate < 0) framebytes = 0;
        }
        if (h->option == 2)
        {
            /* layer II */
            if (h->br_index > 0)
                lBitrate = 1000*mp_br_table[h->id][h->br_index];
            else
                lBitrate = 1000*framebytes*mp_sr20_table[h->id][h->sr_index] / (144*20);
            // Cap the bitrate
            if (lBitrate > 384000 || lBitrate < 0) framebytes = 0;
        }
        if (h->option == 3)
        {
            /* layer I */
            if(h->br_index > 0)
                lBitrate = 1000 * mp_br_tableL1[h->id][h->br_index];
            else
                lBitrate = 1000*framebytes*mp_sr20_table[h->id][h->sr_index] / (48*20);
            // Cap the bitrate
            if (lBitrate > 448000 || lBitrate < 0) framebytes = 0;
        }
    }
}

return framebytes;
}
/*--------------------------------------------------------------*/
int head_info2(unsigned char *buf, unsigned int n, MPEG_HEAD *h, int *br, int trustFrame)
{
int framebytes;

/*---  return br (in bits/sec) in addition to frame bytes ---*/

*br = 0;         /*-- assume fail --*/
framebytes =  head_info(buf, n, h, trustFrame);

if( framebytes == 0 ) return 0;

if( h->option == 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);
        }
    }
}
if( h->option == 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);
}
if( h->option == 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);
}


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;
}