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This commit is contained in:
Scott Wheeler
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mpeg/mpegproperties.cpp
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mpeg/mpegproperties.cpp
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/***************************************************************************
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copyright : (C) 2003 by Scott Wheeler
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email : wheeler@kde.org
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***************************************************************************/
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/***************************************************************************
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* This library is free software; you can redistribute it and/or modify *
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* it under the terms of the GNU Lesser General Public License version *
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* 2.1 as published by the Free Software Foundation. *
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* *
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* This library is distributed in the hope that it will be useful, but *
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* WITHOUT ANY WARRANTY; without even the implied warranty of *
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU *
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* Lesser General Public License for more details. *
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* *
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* You should have received a copy of the GNU Lesser General Public *
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* License along with this library; if not, write to the Free Software *
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 *
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* USA *
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***************************************************************************/
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#include <tdebug.h>
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#include <tstring.h>
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#include "mpegproperties.h"
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#include "mpegfile.h"
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#include "xingheader.h"
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using namespace TagLib;
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class MPEG::Properties::PropertiesPrivate
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{
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public:
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PropertiesPrivate(File *f, ReadStyle s) :
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file(f),
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style(s),
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length(0),
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bitrate(0),
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sampleRate(0),
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channels(0) {}
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File *file;
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ReadStyle style;
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int length;
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int bitrate;
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int sampleRate;
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int channels;
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Header::Version version;
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int layer;
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Header::ChannelMode channelMode;
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bool isCopyrighted;
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bool isOriginal;
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};
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////////////////////////////////////////////////////////////////////////////////
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// public members
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////////////////////////////////////////////////////////////////////////////////
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MPEG::Properties::Properties(File *file, ReadStyle style) : AudioProperties(style)
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{
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d = new PropertiesPrivate(file, style);
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if(file && file->isOpen())
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read();
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}
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MPEG::Properties::~Properties()
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{
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delete d;
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}
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int MPEG::Properties::length() const
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{
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return d->length;
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}
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int MPEG::Properties::bitrate() const
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{
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return d->bitrate;
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}
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int MPEG::Properties::sampleRate() const
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{
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return d->sampleRate;
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}
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int MPEG::Properties::channels() const
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{
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return d->channels;
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}
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MPEG::Header::Version MPEG::Properties::version() const
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{
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return d->version;
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}
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int MPEG::Properties::layer() const
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{
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return d->layer;
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}
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MPEG::Header::ChannelMode MPEG::Properties::channelMode() const
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{
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return d->channelMode;
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}
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bool MPEG::Properties::isCopyrighted() const
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{
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return d->isCopyrighted;
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}
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bool MPEG::Properties::isOriginal() const
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{
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return d->isOriginal;
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}
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////////////////////////////////////////////////////////////////////////////////
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// private members
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////////////////////////////////////////////////////////////////////////////////
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void MPEG::Properties::read()
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{
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// Since we've likely just looked for the ID3v1 tag, start at the end of the
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// file where we're least likely to have to have to move the disk head.
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long last = d->file->lastFrameOffset();
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if(last < 0) {
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debug("MPEG::Properties::read() -- Could not find a valid last MPEG frame in the stream.");
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return;
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}
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d->file->seek(last);
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Header lastHeader(d->file->readBlock(4));
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long first = d->file->firstFrameOffset();
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if(first < 0) {
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debug("MPEG::Properties::read() -- Could not find a valid first MPEG frame in the stream.");
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return;
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}
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if(!lastHeader.isValid()) {
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long pos = last;
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while(pos > first) {
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pos = d->file->previousFrameOffset(pos);
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if(pos < 0)
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break;
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d->file->seek(pos);
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Header header(d->file->readBlock(4));
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if(header.isValid()) {
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lastHeader = header;
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last = pos;
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break;
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}
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}
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}
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// Now jump back to the front of the file and read what we need from there.
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d->file->seek(first);
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Header firstHeader(d->file->readBlock(4));
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if(!firstHeader.isValid() || !lastHeader.isValid()) {
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debug("MPEG::Properties::read() -- Page headers were invalid.");
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return;
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}
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// Check for a Xing header that will help us in gathering information about a
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// VBR stream.
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int xingHeaderOffset = MPEG::XingHeader::xingHeaderOffset(firstHeader.version(),
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firstHeader.channelMode());
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d->file->seek(first + xingHeaderOffset);
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XingHeader xingHeader(d->file->readBlock(16));
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// Read the length and the bitrate from the Xing header.
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if(xingHeader.isValid() &&
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firstHeader.sampleRate() > 0 &&
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xingHeader.totalFrames() > 0)
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{
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static const int blockSize[] = { 0, 384, 1152, 1152 };
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double timePerFrame = blockSize[firstHeader.layer()];
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timePerFrame = timePerFrame / firstHeader.sampleRate();
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d->length = int(timePerFrame * xingHeader.totalFrames());
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d->bitrate = xingHeader.totalSize() * 8 / d->length / 1000;
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}
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// Since there was no valid Xing header found, we hope that we're in a constant
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// bitrate file.
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// TODO: Make this more robust with audio property detection for VBR without a
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// Xing header.
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else if(firstHeader.frameLength() > 0 && firstHeader.bitrate() > 0) {
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int frames = (last - first) / firstHeader.frameLength() + 1;
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d->length = int(float(firstHeader.frameLength() * frames) /
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float(firstHeader.bitrate() * 125) + 0.5);
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d->bitrate = firstHeader.bitrate();
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}
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d->sampleRate = firstHeader.sampleRate();
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d->channels = firstHeader.channelMode() == Header::SingleChannel ? 1 : 2;
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d->version = firstHeader.version();
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d->layer = firstHeader.layer();
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d->channelMode = firstHeader.channelMode();
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d->isCopyrighted = firstHeader.isCopyrighted();
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d->isOriginal = firstHeader.isOriginal();
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}
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