diff --git a/taglib/mp4/mp4file.cpp b/taglib/mp4/mp4file.cpp
index e3cb02a3..1fc1524f 100644
--- a/taglib/mp4/mp4file.cpp
+++ b/taglib/mp4/mp4file.cpp
@@ -32,12 +32,30 @@
 
 using namespace TagLib;
 
+namespace
+{
+  bool checkValid(const MP4::AtomList &list)
+  {
+    for(MP4::AtomList::ConstIterator it = list.begin(); it != list.end(); ++it) {
+
+      if((*it)->length == 0)
+        return false;
+
+      if(!checkValid((*it)->children))
+        return false;
+    }
+
+    return true;
+  }
+}
+
 class MP4::File::FilePrivate
 {
 public:
-  FilePrivate() : tag(0), atoms(0), properties(0)
-  {
-  }
+  FilePrivate() :
+    tag(0),
+    atoms(0),
+    properties(0) {}
 
   ~FilePrivate()
   {
@@ -46,25 +64,25 @@ public:
     delete properties;
   }
 
-  MP4::Tag *tag;
-  MP4::Atoms *atoms;
+  MP4::Tag        *tag;
+  MP4::Atoms      *atoms;
   MP4::Properties *properties;
 };
 
-MP4::File::File(FileName file, bool readProperties, AudioProperties::ReadStyle audioPropertiesStyle)
-    : TagLib::File(file)
+MP4::File::File(FileName file, bool readProperties, AudioProperties::ReadStyle) :
+  TagLib::File(file),
+  d(new FilePrivate())
 {
-  d = new FilePrivate;
   if(isOpen())
-    read(readProperties, audioPropertiesStyle);
+    read(readProperties);
 }
 
-MP4::File::File(IOStream *stream, bool readProperties, AudioProperties::ReadStyle audioPropertiesStyle)
-    : TagLib::File(stream)
+MP4::File::File(IOStream *stream, bool readProperties, AudioProperties::ReadStyle) :
+  TagLib::File(stream),
+  d(new FilePrivate())
 {
-  d = new FilePrivate;
   if(isOpen())
-    read(readProperties, audioPropertiesStyle);
+    read(readProperties);
 }
 
 MP4::File::~File()
@@ -99,26 +117,14 @@ MP4::File::audioProperties() const
   return d->properties;
 }
 
-bool
-MP4::File::checkValid(const MP4::AtomList &list)
-{
-  for(uint i = 0; i < list.size(); i++) {
-    if(list[i]->length == 0)
-      return false;
-    if(!checkValid(list[i]->children))
-      return false;
-  }
-  return true;
-}
-
 void
-MP4::File::read(bool readProperties, Properties::ReadStyle audioPropertiesStyle)
+MP4::File::read(bool readProperties)
 {
   if(!isValid())
     return;
 
   d->atoms = new Atoms(this);
-  if (!checkValid(d->atoms->atoms)) {
+  if(!checkValid(d->atoms->atoms)) {
     setValid(false);
     return;
   }
@@ -132,7 +138,7 @@ MP4::File::read(bool readProperties, Properties::ReadStyle audioPropertiesStyle)
 
   d->tag = new Tag(this, d->atoms);
   if(readProperties) {
-    d->properties = new Properties(this, d->atoms, audioPropertiesStyle);
+    d->properties = new Properties(this, d->atoms);
   }
 }
 
diff --git a/taglib/mp4/mp4file.h b/taglib/mp4/mp4file.h
index a19eb074..28880f84 100644
--- a/taglib/mp4/mp4file.h
+++ b/taglib/mp4/mp4file.h
@@ -115,9 +115,7 @@ namespace TagLib {
       bool save();
 
     private:
-
-      void read(bool readProperties, Properties::ReadStyle audioPropertiesStyle);
-      bool checkValid(const MP4::AtomList &list);
+      void read(bool readProperties);
 
       class FilePrivate;
       FilePrivate *d;
diff --git a/taglib/mp4/mp4properties.cpp b/taglib/mp4/mp4properties.cpp
index 5a41c081..0ac77342 100644
--- a/taglib/mp4/mp4properties.cpp
+++ b/taglib/mp4/mp4properties.cpp
@@ -34,7 +34,14 @@ using namespace TagLib;
 class MP4::Properties::PropertiesPrivate
 {
 public:
-  PropertiesPrivate() : length(0), bitrate(0), sampleRate(0), channels(0), bitsPerSample(0), encrypted(false), codec(MP4::Properties::Unknown) {}
+  PropertiesPrivate() :
+    length(0),
+    bitrate(0),
+    sampleRate(0),
+    channels(0),
+    bitsPerSample(0),
+    encrypted(false),
+    codec(MP4::Properties::Unknown) {}
 
   int length;
   int bitrate;
@@ -45,110 +52,15 @@ public:
   Codec codec;
 };
 
-MP4::Properties::Properties(File *file, MP4::Atoms *atoms, ReadStyle style)
-  : AudioProperties(style)
+////////////////////////////////////////////////////////////////////////////////
+// public members
+////////////////////////////////////////////////////////////////////////////////
+
+MP4::Properties::Properties(File *file, MP4::Atoms *atoms, ReadStyle style) :
+  AudioProperties(style),
+  d(new PropertiesPrivate())
 {
-  d = new PropertiesPrivate;
-
-  MP4::Atom *moov = atoms->find("moov");
-  if(!moov) {
-    debug("MP4: Atom 'moov' not found");
-    return;
-  }
-
-  MP4::Atom *trak = 0;
-  ByteVector data;
-
-  MP4::AtomList trakList = moov->findall("trak");
-  for (unsigned int i = 0; i < trakList.size(); i++) {
-    trak = trakList[i];
-    MP4::Atom *hdlr = trak->find("mdia", "hdlr");
-    if(!hdlr) {
-      debug("MP4: Atom 'trak.mdia.hdlr' not found");
-      return;
-    }
-    file->seek(hdlr->offset);
-    data = file->readBlock(hdlr->length);
-    if(data.mid(16, 4) == "soun") {
-      break;
-    }
-    trak = 0;
-  }
-  if (!trak) {
-    debug("MP4: No audio tracks");
-    return;
-  }
-
-  MP4::Atom *mdhd = trak->find("mdia", "mdhd");
-  if(!mdhd) {
-    debug("MP4: Atom 'trak.mdia.mdhd' not found");
-    return;
-  }
-
-  file->seek(mdhd->offset);
-  data = file->readBlock(mdhd->length);
-  uint version = data[8];
-  if(version == 1) {
-    if (data.size() < 36 + 8) {
-      debug("MP4: Atom 'trak.mdia.mdhd' is smaller than expected");
-      return;
-    }
-    const long long unit   = data.toLongLong(28U);
-    const long long length = data.toLongLong(36U);
-    d->length = unit ? int(length / unit) : 0;
-  }
-  else {
-    if (data.size() < 24 + 4) {
-      debug("MP4: Atom 'trak.mdia.mdhd' is smaller than expected");
-      return;
-    }
-    const unsigned int unit   = data.toUInt(20U);
-    const unsigned int length = data.toUInt(24U);
-    d->length = unit ? length / unit : 0;
-  }
-
-  MP4::Atom *atom = trak->find("mdia", "minf", "stbl", "stsd");
-  if(!atom) {
-    return;
-  }
-
-  file->seek(atom->offset);
-  data = file->readBlock(atom->length);
-  if(data.mid(20, 4) == "mp4a") {
-    d->codec         = AAC;
-    d->channels      = data.toShort(40U);
-    d->bitsPerSample = data.toShort(42U);
-    d->sampleRate    = data.toUInt(46U);
-    if(data.mid(56, 4) == "esds" && data[64] == 0x03) {
-      uint pos = 65;
-      if(data.mid(pos, 3) == "\x80\x80\x80") {
-        pos += 3;
-      }
-      pos += 4;
-      if(data[pos] == 0x04) {
-        pos += 1;
-        if(data.mid(pos, 3) == "\x80\x80\x80") {
-          pos += 3;
-        }
-        pos += 10;
-        d->bitrate = (data.toUInt(pos) + 500) / 1000;
-      }
-    }
-  }
-  else if (data.mid(20, 4) == "alac") {
-    if (atom->length == 88 && data.mid(56, 4) == "alac") {
-      d->codec         = ALAC;
-      d->bitsPerSample = data.at(69);
-      d->channels      = data.at(73);
-      d->bitrate       = data.toUInt(80U) / 1000;
-      d->sampleRate    = data.toUInt(84U);
-    }
-  }
-
-  MP4::Atom *drms = atom->find("drms");
-  if(drms) {
-    d->encrypted = true;
-  }
+  read(file, atoms);
 }
 
 MP4::Properties::~Properties()
@@ -170,6 +82,18 @@ MP4::Properties::sampleRate() const
 
 int
 MP4::Properties::length() const
+{
+  return lengthInSeconds();
+}
+
+int
+MP4::Properties::lengthInSeconds() const
+{
+  return d->length / 1000;
+}
+
+int
+MP4::Properties::lengthInMilliseconds() const
 {
   return d->length;
 }
@@ -192,8 +116,119 @@ MP4::Properties::isEncrypted() const
   return d->encrypted;
 }
 
-MP4::Properties::Codec MP4::Properties::codec() const
+MP4::Properties::Codec
+MP4::Properties::codec() const
 {
   return d->codec;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+// private members
+////////////////////////////////////////////////////////////////////////////////
+
+void
+MP4::Properties::read(File *file, Atoms *atoms)
+{
+  MP4::Atom *moov = atoms->find("moov");
+  if(!moov) {
+    debug("MP4: Atom 'moov' not found");
+    return;
+  }
+
+  MP4::Atom *trak = 0;
+  ByteVector data;
+
+  const MP4::AtomList trakList = moov->findall("trak");
+  for(MP4::AtomList::ConstIterator it = trakList.begin(); it != trakList.end(); ++it) {
+    trak = *it;
+    MP4::Atom *hdlr = trak->find("mdia", "hdlr");
+    if(!hdlr) {
+      debug("MP4: Atom 'trak.mdia.hdlr' not found");
+      return;
+    }
+    file->seek(hdlr->offset);
+    data = file->readBlock(hdlr->length);
+    if(data.containsAt("soun", 16)) {
+      break;
+    }
+    trak = 0;
+  }
+  if(!trak) {
+    debug("MP4: No audio tracks");
+    return;
+  }
+
+  MP4::Atom *mdhd = trak->find("mdia", "mdhd");
+  if(!mdhd) {
+    debug("MP4: Atom 'trak.mdia.mdhd' not found");
+    return;
+  }
+
+  file->seek(mdhd->offset);
+  data = file->readBlock(mdhd->length);
+
+  const uint version = data[8];
+  long long unit;
+  long long length;
+  if(version == 1) {
+    if(data.size() < 36 + 8) {
+      debug("MP4: Atom 'trak.mdia.mdhd' is smaller than expected");
+      return;
+    }
+    unit   = data.toLongLong(28U);
+    length = data.toLongLong(36U);
+  }
+  else {
+    if(data.size() < 24 + 4) {
+      debug("MP4: Atom 'trak.mdia.mdhd' is smaller than expected");
+      return;
+    }
+    unit   = data.toUInt(20U);
+    length = data.toUInt(24U);
+  }
+  if(unit > 0 && length > 0)
+    d->length = static_cast<int>(length * 1000.0 / unit);
+
+  MP4::Atom *atom = trak->find("mdia", "minf", "stbl", "stsd");
+  if(!atom) {
+    return;
+  }
+
+  file->seek(atom->offset);
+  data = file->readBlock(atom->length);
+  if(data.containsAt("mp4a", 20)) {
+    d->codec         = AAC;
+    d->channels      = data.toShort(40U);
+    d->bitsPerSample = data.toShort(42U);
+    d->sampleRate    = data.toUInt(46U);
+    if(data.containsAt("esds", 56) && data[64] == 0x03) {
+      uint pos = 65;
+      if(data.containsAt("\x80\x80\x80", pos)) {
+        pos += 3;
+      }
+      pos += 4;
+      if(data[pos] == 0x04) {
+        pos += 1;
+        if(data.containsAt("\x80\x80\x80", pos)) {
+          pos += 3;
+        }
+        pos += 10;
+        d->bitrate = static_cast<int>((data.toUInt(pos) + 500) / 1000.0 + 0.5);
+      }
+    }
+  }
+  else if(data.containsAt("alac", 20)) {
+    if(atom->length == 88 && data.containsAt("alac", 56)) {
+      d->codec         = ALAC;
+      d->bitsPerSample = data.at(69);
+      d->channels      = data.at(73);
+      d->bitrate       = static_cast<int>(data.toUInt(80U) / 1000.0 + 0.5);
+      d->sampleRate    = data.toUInt(84U);
+    }
+  }
+
+  MP4::Atom *drms = atom->find("drms");
+  if(drms) {
+    d->encrypted = true;
+  }
+}
diff --git a/taglib/mp4/mp4properties.h b/taglib/mp4/mp4properties.h
index 2607c366..410d5348 100644
--- a/taglib/mp4/mp4properties.h
+++ b/taglib/mp4/mp4properties.h
@@ -49,17 +49,66 @@ namespace TagLib {
       Properties(File *file, Atoms *atoms, ReadStyle style = Average);
       virtual ~Properties();
 
+      /*!
+       * Returns the length of the file in seconds.  The length is rounded down to
+       * the nearest whole second.
+       *
+       * \note This method is just an alias of lengthInSeconds().
+       *
+       * \deprecated
+       */
       virtual int length() const;
+
+      /*!
+       * Returns the length of the file in seconds.  The length is rounded down to
+       * the nearest whole second.
+       *
+       * \see lengthInMilliseconds()
+       */
+      // BIC: make virtual
+      int lengthInSeconds() const;
+
+      /*!
+       * Returns the length of the file in milliseconds.
+       *
+       * \see lengthInSeconds()
+       */
+      // BIC: make virtual
+      int lengthInMilliseconds() const;
+
+      /*!
+       * Returns the average bit rate of the file in kb/s.
+       */
       virtual int bitrate() const;
+
+      /*!
+       * Returns the sample rate in Hz.
+       */
       virtual int sampleRate() const;
+
+      /*!
+       * Returns the number of audio channels.
+       */
       virtual int channels() const;
+
+      /*!
+       * Returns the number of bits per audio sample.
+       */
       virtual int bitsPerSample() const;
+
+      /*!
+       * Returns whether or not the file is encrypted.
+       */
       bool isEncrypted() const;
 
-      //! Audio codec used in the MP4 file
+      /*!
+       * Returns the codec used in the file.
+       */
       Codec codec() const;
 
     private:
+      void read(File *file, Atoms *atoms);
+
       class PropertiesPrivate;
       PropertiesPrivate *d;
     };
diff --git a/tests/test_mp4.cpp b/tests/test_mp4.cpp
index dd6e3a03..78e1badf 100644
--- a/tests/test_mp4.cpp
+++ b/tests/test_mp4.cpp
@@ -36,23 +36,31 @@ public:
   void testPropertiesAAC()
   {
     MP4::File f(TEST_FILE_PATH_C("has-tags.m4a"));
+    CPPUNIT_ASSERT(f.audioProperties());
     CPPUNIT_ASSERT_EQUAL(3, f.audioProperties()->length());
+    CPPUNIT_ASSERT_EQUAL(3, f.audioProperties()->lengthInSeconds());
+    CPPUNIT_ASSERT_EQUAL(3707, f.audioProperties()->lengthInMilliseconds());
     CPPUNIT_ASSERT_EQUAL(3, f.audioProperties()->bitrate());
     CPPUNIT_ASSERT_EQUAL(2, f.audioProperties()->channels());
     CPPUNIT_ASSERT_EQUAL(44100, f.audioProperties()->sampleRate());
-    CPPUNIT_ASSERT_EQUAL(16, ((MP4::Properties *)f.audioProperties())->bitsPerSample());
-    CPPUNIT_ASSERT_EQUAL(MP4::Properties::AAC, ((MP4::Properties *)f.audioProperties())->codec());
+    CPPUNIT_ASSERT_EQUAL(16, f.audioProperties()->bitsPerSample());
+    CPPUNIT_ASSERT_EQUAL(false, f.audioProperties()->isEncrypted());
+    CPPUNIT_ASSERT_EQUAL(MP4::Properties::AAC, f.audioProperties()->codec());
   }
 
   void testPropertiesALAC()
   {
     MP4::File f(TEST_FILE_PATH_C("empty_alac.m4a"));
+    CPPUNIT_ASSERT(f.audioProperties());
     CPPUNIT_ASSERT_EQUAL(3, f.audioProperties()->length());
-    CPPUNIT_ASSERT_EQUAL(2, f.audioProperties()->bitrate());
+    CPPUNIT_ASSERT_EQUAL(3, f.audioProperties()->lengthInSeconds());
+    CPPUNIT_ASSERT_EQUAL(3705, f.audioProperties()->lengthInMilliseconds());
+    CPPUNIT_ASSERT_EQUAL(3, f.audioProperties()->bitrate());
     CPPUNIT_ASSERT_EQUAL(2, f.audioProperties()->channels());
     CPPUNIT_ASSERT_EQUAL(44100, f.audioProperties()->sampleRate());
-    CPPUNIT_ASSERT_EQUAL(16, ((MP4::Properties *)f.audioProperties())->bitsPerSample());
-    CPPUNIT_ASSERT_EQUAL(MP4::Properties::ALAC, ((MP4::Properties *)f.audioProperties())->codec());
+    CPPUNIT_ASSERT_EQUAL(16, f.audioProperties()->bitsPerSample());
+    CPPUNIT_ASSERT_EQUAL(false, f.audioProperties()->isEncrypted());
+    CPPUNIT_ASSERT_EQUAL(MP4::Properties::ALAC, f.audioProperties()->codec());
   }
 
   void testCheckValid()