mp3_parse.cpp

本人收集整理的一份c/c++跨平台网络库

// -*- C++ -*-
// $Id: mp3_parse.cpp,v 1.6 2002/11/02 17:48:51 t1mpy Exp $

// id3lib: a C++ library for creating and manipulating id3v1/v2 tags
// Copyright 2002, Thijmen Klok ([e-mail])

// This library 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 library 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 library; if not, write to the Free Software Foundation,
// Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

// The id3lib authors encourage improvements and optimisations to be sent to
// the id3lib coordinator.  Please see the README file for details on where to
// send such submissions.  See the AUTHORS file for a list of people who have
// contributed to id3lib.  See the ChangeLog file for a list of changes to
// id3lib.  These files are distributed with id3lib at
// http://download.sourceforge.net/id3lib/

#include "mp3_header.h"

#define FRAMES_FLAG     0x0001
#define BYTES_FLAG      0x0002
#define TOC_FLAG        0x0004
#define SCALE_FLAG      0x0008

static int ExtractI4(unsigned char *buf)
{
  int x;
  // big endian extract

  x = buf[0];
  x <<= 8;
  x |= buf[1];
  x <<= 8;
  x |= buf[2];
  x <<= 8;
  x |= buf[3];

  return x;
}

uint32 fto_nearest_i(float f)
{
  uint32 i;

  i = (uint32)f;
  if (i < f)
  {
    f -= i;
      if (f >= 0.5)
      return i+1;
    else
      return i;
  }
  else
    return i;
}

uint16 calcCRC(char *pFrame, size_t audiodatasize)
{
  size_t icounter;
  int tmpchar, crcmask, tmpi;
  uint16 crc = 0xffff;

  for (icounter = 2;  icounter < audiodatasize;  ++icounter)
  {
    if (icounter != 4  &&  icounter != 5) //skip the 2 chars of the crc itself
    {
      crcmask = 1 << 8;
      tmpchar = pFrame[icounter];
      while (crcmask >>= 1)
      {
        tmpi = crc & 0x8000;
        crc <<= 1;
        if (!tmpi ^ !(tmpchar & crcmask))
          crc ^= 0x8005;
      }
    }
  }
  crc &= 0xffff;
  return crc;
}

void Mp3Info::Clean()
{
  if (_mp3_header_output != NULL)
    delete _mp3_header_output;
  _mp3_header_output = NULL;
}

using namespace dami;

bool Mp3Info::Parse(ID3_Reader& reader, size_t mp3size)
{
  MP3_BitRates _mp3_bitrates[2][3][16] =
  {
    {
      { //MPEG 1, LAYER I
        MP3BITRATE_NONE,
        MP3BITRATE_32K,
        MP3BITRATE_64K,
        MP3BITRATE_96K,
        MP3BITRATE_128K,
        MP3BITRATE_160K,
        MP3BITRATE_192K,
        MP3BITRATE_224K,
        MP3BITRATE_256K,
        MP3BITRATE_288K,
        MP3BITRATE_320K,
        MP3BITRATE_352K,
        MP3BITRATE_384K,
        MP3BITRATE_416K,
        MP3BITRATE_448K,
        MP3BITRATE_FALSE
      },
      { //MPEG 1, LAYER II
        MP3BITRATE_NONE,
        MP3BITRATE_32K,
        MP3BITRATE_48K,
        MP3BITRATE_56K,
        MP3BITRATE_64K,
        MP3BITRATE_80K,
        MP3BITRATE_96K,
        MP3BITRATE_112K,
        MP3BITRATE_128K,
        MP3BITRATE_160K,
        MP3BITRATE_192K,
        MP3BITRATE_224K,
        MP3BITRATE_256K,
        MP3BITRATE_320K,
        MP3BITRATE_384K,
        MP3BITRATE_FALSE
      },
      { //MPEG 1, LAYER III
        MP3BITRATE_NONE,
        MP3BITRATE_32K,
        MP3BITRATE_40K,
        MP3BITRATE_48K,
        MP3BITRATE_56K,
        MP3BITRATE_64K,
        MP3BITRATE_80K,
        MP3BITRATE_96K,
        MP3BITRATE_112K,
        MP3BITRATE_128K,
        MP3BITRATE_160K,
        MP3BITRATE_192K,
        MP3BITRATE_224K,
        MP3BITRATE_256K,
        MP3BITRATE_320K,
        MP3BITRATE_FALSE
      }
    },
    {
      { //MPEG 2 or 2.5, LAYER I
        MP3BITRATE_NONE,
        MP3BITRATE_32K,
        MP3BITRATE_48K,
        MP3BITRATE_56K,
        MP3BITRATE_64K,
        MP3BITRATE_80K,
        MP3BITRATE_96K,
        MP3BITRATE_112K,
        MP3BITRATE_128K,
        MP3BITRATE_144K,
        MP3BITRATE_160K,
        MP3BITRATE_176K,
        MP3BITRATE_192K,
        MP3BITRATE_224K,
        MP3BITRATE_256K,
        MP3BITRATE_FALSE
      },
      { //MPEG 2 or 2.5, LAYER II
        MP3BITRATE_NONE,
        MP3BITRATE_8K,
        MP3BITRATE_16K,
        MP3BITRATE_24K,
        MP3BITRATE_32K,
        MP3BITRATE_40K,
        MP3BITRATE_48K,
        MP3BITRATE_56K,
        MP3BITRATE_64K,
        MP3BITRATE_80K,
        MP3BITRATE_96K,
        MP3BITRATE_112K,
        MP3BITRATE_128K,
        MP3BITRATE_144K,
        MP3BITRATE_160K,
        MP3BITRATE_FALSE
      },
      { //MPEG 2 or 2.5, LAYER III
        MP3BITRATE_NONE,
        MP3BITRATE_8K,
        MP3BITRATE_16K,
        MP3BITRATE_24K,
        MP3BITRATE_32K,
        MP3BITRATE_40K,
        MP3BITRATE_48K,
        MP3BITRATE_56K,
        MP3BITRATE_64K,
        MP3BITRATE_80K,
        MP3BITRATE_96K,
        MP3BITRATE_112K,
        MP3BITRATE_128K,
        MP3BITRATE_144K,
        MP3BITRATE_160K,
        MP3BITRATE_FALSE
      }
    }
  };

  Mp3_Frequencies _mp3_frequencies[4][4] =
  {
    { MP3FREQUENCIES_11025HZ, MP3FREQUENCIES_12000HZ, MP3FREQUENCIES_8000HZ,MP3FREQUENCIES_Reserved },  //MPEGVERSION_2_5
    { MP3FREQUENCIES_Reserved, MP3FREQUENCIES_Reserved, MP3FREQUENCIES_Reserved, MP3FREQUENCIES_Reserved},          //MPEGVERSION_Reserved
    { MP3FREQUENCIES_22050HZ, MP3FREQUENCIES_24000HZ, MP3FREQUENCIES_16000HZ, MP3FREQUENCIES_Reserved }, //MPEGVERSION_2
    { MP3FREQUENCIES_44100HZ, MP3FREQUENCIES_48000HZ, MP3FREQUENCIES_32000HZ, MP3FREQUENCIES_Reserved }  //MPEGVERSION_1
  };

  _mp3_header_internal *_tmpheader;

  const size_t HEADERSIZE = 4;//
  char buf[HEADERSIZE+1]; //+1 to hold the \0 char
  ID3_Reader::pos_type beg = reader.getCur() ;
  ID3_Reader::pos_type end = beg + HEADERSIZE ;
  reader.setCur(beg);
  int bitrate_index;

  _mp3_header_output->layer = MPEGLAYER_FALSE;
  _mp3_header_output->version = MPEGVERSION_FALSE;
  _mp3_header_output->bitrate = MP3BITRATE_FALSE;
  _mp3_header_output->channelmode = MP3CHANNELMODE_FALSE;
  _mp3_header_output->modeext = MP3MODEEXT_FALSE;
  _mp3_header_output->emphasis = MP3EMPHASIS_FALSE;
  _mp3_header_output->crc = MP3CRC_MISMATCH;
  _mp3_header_output->frequency = 0;
  _mp3_header_output->framesize = 0;
  _mp3_header_output->frames = 0;
  _mp3_header_output->time = 0;
  _mp3_header_output->vbr_bitrate = 0;

  reader.readChars(buf, HEADERSIZE);
  buf[HEADERSIZE]='\0';
  // copy the pointer to the struct

  if (((buf[0] & 0xFF) != 0xFF) || ((buf[1] & 0xE0) != 0xE0)) //first 11 bits should be 1
  {
    this->Clean();
    return false;
  }

  _tmpheader = reinterpret_cast<_mp3_header_internal *>(buf);

  bitrate_index = 0;
  switch (_tmpheader->id)
  {
    case 3:
      _mp3_header_output->version = MPEGVERSION_1;
      bitrate_index = 0;
      break;
    case 2:
      _mp3_header_output->version = MPEGVERSION_2;
      bitrate_index = 1;
      break;
    case 1:
      this->Clean();
      return false; //wouldn't know how to handle it
      break;
    case 0:
      _mp3_header_output->version = MPEGVERSION_2_5;
      bitrate_index = 1;
      break;
    default:
      this->Clean();
      return false;
      break;
  };