wvproperties.cpp

来自「Amarok是一款在LINUX或其他类UNIX操作系统中运行的音频播放器软件。 」· C++ 代码 · 共 142 行

/***************************************************************************
    copyright            : (C) 2006 by Lukáš Lalinský
    email                : [e-mail]
    
    copyright            : (C) 2004 by Allan Sandfeld Jensen 
    email                : [e-mail] 
                           (original MPC implementation)
 ***************************************************************************/

/***************************************************************************
 *   This library is free software; you can redistribute it and/or modify  *
 *   it  under the terms of the GNU Lesser General Public License version  *
 *   2.1 as published by the Free Software Foundation.                     *
 *                                                                         *
 *   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     *
 *   Lesser General Public License for more details.                       *
 *                                                                         *
 *   You should have received a copy of the GNU Lesser General Public      *
 *   License along with this library; if not, write to the Free Software   *
 *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,            *
 *   MA  02110-1301  USA                                                   *
 ***************************************************************************/

#include <tstring.h>
#if 0
#include <tdebug.h>
#endif
#include <bitset>

#include "wvproperties.h"
#include "wvfile.h"

using namespace TagLib;

class WavPack::Properties::PropertiesPrivate
{
public:
  PropertiesPrivate(const ByteVector &d, long length, ReadStyle s) :
    data(d),
    streamLength(length), 
    style(s),
    length(0),
    bitrate(0),
    sampleRate(0),
    channels(0),
    version(0),
    bitsPerSample(0) {}

  ByteVector data;
  long streamLength; 
  ReadStyle style;
  int length;
  int bitrate;
  int sampleRate;
  int channels;
  int version;
  int bitsPerSample;
};

////////////////////////////////////////////////////////////////////////////////
// public members
////////////////////////////////////////////////////////////////////////////////

WavPack::Properties::Properties(const ByteVector &data, long streamLength, ReadStyle style) : AudioProperties(style)
{
  d = new PropertiesPrivate(data, streamLength, style);
  read();
}

WavPack::Properties::~Properties()
{
  delete d;
}

int WavPack::Properties::length() const
{
  return d->length;
}

int WavPack::Properties::bitrate() const
{
  return d->bitrate;
}

int WavPack::Properties::sampleRate() const
{
  return d->sampleRate;
}

int WavPack::Properties::channels() const
{
  return d->channels;
}

int WavPack::Properties::version() const
{
  return d->version;
}

int WavPack::Properties::bitsPerSample() const
{
  return d->bitsPerSample;
}

////////////////////////////////////////////////////////////////////////////////
// private members
////////////////////////////////////////////////////////////////////////////////

static const unsigned int sample_rates[] = { 6000, 8000, 9600, 11025, 12000,
    16000, 22050, 24000, 32000, 44100, 48000, 64000, 88200, 96000, 192000 };

#define BYTES_STORED    3
#define MONO_FLAG       4
    
#define SHIFT_LSB       13
#define SHIFT_MASK      (0x1fL << SHIFT_LSB)

#define SRATE_LSB       23
#define SRATE_MASK      (0xfL << SRATE_LSB)
    
void WavPack::Properties::read()
{
  if(!d->data.startsWith("wvpk"))
    return;

  d->version = d->data.mid(8, 2).toShort(false);
  
  unsigned int flags = d->data.mid(24, 4).toUInt(false);
  d->bitsPerSample = ((flags & BYTES_STORED) + 1) * 8 -
    ((flags & SHIFT_MASK) >> SHIFT_LSB);
  d->sampleRate = sample_rates[(flags & SRATE_MASK) >> SRATE_LSB];
  d->channels = (flags & MONO_FLAG) ? 1 : 2;
  
  unsigned int samples = d->data.mid(12, 4).toUInt(false);
  d->length = d->sampleRate > 0 ? (samples + (d->sampleRate / 2)) / d->sampleRate : 0;
  
  d->bitrate = d->length > 0 ? ((d->streamLength * 8L) / d->length) / 1000 : 0;
}