/// <summary>
/// Reads an audio packet, assigning the audio header and
/// advancing the position to the next packet position.
/// </summary>
/// <param name="position">
/// A <see cref="long" /> value reference specifying the
/// position at which to start reading the packet. This value
/// is updated to the position of the next packet.
/// </param>
void ReadAudioPacket(ref long position)
{
Seek(position + 4);
int length = ReadBlock(2).ToUShort();
if (!audio_found)
{
// There is a maximum of 16 stuffing bytes, read up to the PTS/DTS flags
ByteVector packetHeaderBytes = this.ReadBlock(19);
int i = 0;
while (i < packetHeaderBytes.Count && packetHeaderBytes[i] == 0xFF)
{
// Byte is a stuffing byte
i++;
}
if ((packetHeaderBytes[i] & 0x40) != 0)
{
// STD buffer size is unexpected for audio packets, but whatever
i++;
}
// Decode the PTS/DTS flags
byte timestampFlags = packetHeaderBytes[i];
long dataOffset = 4 + 2 + i + // Packet marker + packet length + stuffing bytes/STD buffer size
((timestampFlags & 0x20) > 0 ? 4 : 0) + // Presentation timestamp
((timestampFlags & 0x10) > 0 ? 4 : 0); // Decode timestamp
audio_found = AudioHeader.Find(out audio_header, this, position + dataOffset, length - 9);
}
position += length;
}
protected override void ReadStart(long start, ReadStyle propertiesStyle)
{
if (propertiesStyle != ReadStyle.None && !AudioHeader.Find(out first_header, this, start, 0x4000))
{
throw new CorruptFileException("MPEG audio header not found.");
}
}
static AudioHeader()
{
sample_rates = new int[,] { { 0xac44, 0xbb80, 0x7d00, 0 }, { 0x5622, 0x5dc0, 0x3e80, 0 }, { 0x2b11, 0x2ee0, 0x1f40, 0 } };
block_size = new int[,] { { 0, 0x180, 0x480, 0x480 }, { 0, 0x180, 0x480, 0x240 }, { 0, 0x180, 0x480, 0x240 } };
bitrates = new int[,,] { { { 0, 0x20, 0x40, 0x60, 0x80, 160, 0xc0, 0xe0, 0x100, 0x120, 320, 0x160, 0x180, 0x1a0, 0x1c0, -1 }, { 0, 0x20, 0x30, 0x38, 0x40, 80, 0x60, 0x70, 0x80, 160, 0xc0, 0xe0, 0x100, 320, 0x180, -1 }, { 0, 0x20, 40, 0x30, 0x38, 0x40, 80, 0x60, 0x70, 0x80, 160, 0xc0, 0xe0, 0x100, 320, -1 } }, { { 0, 0x20, 0x30, 0x38, 0x40, 80, 0x60, 0x70, 0x80, 0x90, 160, 0xb0, 0xc0, 0xe0, 0x100, -1 }, { 0, 8, 0x10, 0x18, 0x20, 40, 0x30, 0x38, 0x40, 80, 0x60, 0x70, 0x80, 0x90, 160, -1 }, { 0, 8, 0x10, 0x18, 0x20, 40, 0x30, 0x38, 0x40, 80, 0x60, 0x70, 0x80, 0x90, 160, -1 } } };
Unknown = new AudioHeader(0, 0L, TagLib.Mpeg.XingHeader.Unknown, TagLib.Mpeg.VBRIHeader.Unknown);
}
/// <summary>
/// Reads format specific information at the start of the
/// file.
/// </summary>
/// <param name="start">
/// A <see cref="long" /> value containing the seek position
/// at which the tags end and the media data begins.
/// </param>
/// <param name="propertiesStyle">
/// A <see cref="ReadStyle" /> value specifying at what level
/// of accuracy to read the media properties, or <see
/// cref="ReadStyle.None" /> to ignore the properties.
/// </param>
/// <remarks>
/// This method only searches for an audio header in the
/// first 16384 bytes of code to avoid searching forever in
/// corrupt files.
/// </remarks>
protected override void ReadStart(long start, ReadStyle propertiesStyle)
{
// Only check the first 16 bytes so we're not stuck
// reading a bad file forever.
if ((propertiesStyle & ReadStyle.Average) != 0 &&
!AudioHeader.Find(out first_header, this, start, 0x4000))
{
throw new CorruptFileException("MPEG audio header not found.");
}
}
/// <summary>
/// Searches for an audio header in a <see cref="TagLib.File"
/// /> starting at a specified position and searching through
/// a specified number of bytes.
/// </summary>
/// <param name="header">
/// A <see cref="AudioHeader" /> object in which the found
/// header will be stored.
/// </param>
/// <param name="file">
/// A <see cref="TagLib.File" /> object to search.
/// </param>
/// <param name="position">
/// A <see cref="long" /> value specifying the seek position
/// in <paramref name="file" /> at which to start searching.
/// </param>
/// <param name="length">
/// A <see cref="int" /> value specifying the maximum number
/// of bytes to search before aborting.
/// </param>
/// <returns>
/// A <see cref="bool" /> value indicating whether or not a
/// header was found.
/// </returns>
/// <exception cref="ArgumentNullException">
/// <paramref name="file" /> is <see langword="null" />.
/// </exception>
public static bool Find(out AudioHeader header,
TagLib.File file, long position,
int length)
{
if (file == null)
{
throw new ArgumentNullException("file");
}
long end = position + length;
header = AudioHeader.Unknown;
file.Seek(position);
ByteVector buffer = file.ReadBlock(3);
if (buffer.Count < 3)
{
return(false);
}
do
{
file.Seek(position + 3);
buffer = buffer.Mid(buffer.Count - 3);
buffer.Add(file.ReadBlock(
(int)File.BufferSize));
for (int i = 0; i < buffer.Count - 3 &&
(length < 0 || position + i < end); i++)
{
if (buffer [i] == 0xFF &&
buffer [i + 1] > 0xE0)
{
ByteVector data = buffer.Mid(i, 4);
if (GetHeaderError(data) == null)
{
try {
header = new AudioHeader(
data,
file, position + i);
return(true);
} catch (CorruptFileException) {
}
}
}
}
position += File.BufferSize;
} while (buffer.Count > 3 && (length < 0 || position < end));
return(false);
}
/// <summary>
/// Reads an audio packet, assigning the audio header and
/// advancing the position to the next packet position.
/// </summary>
/// <param name="position">
/// A <see cref="long" /> value reference specifying the
/// position at which to start reading the packet. This value
/// is updated to the position of the next packet.
/// </param>
void ReadAudioPacket(ref long position)
{
Seek(position + 4);
int length = ReadBlock(2).ToUShort();
if (!audio_found)
{
audio_found = AudioHeader.Find(out audio_header, this, position + 15, length - 9);
}
position += length;
}
/// <summary>
/// Searches for an audio header in a <see cref="TagLib.File"
/// /> starting at a specified position and searching to the
/// end of the file.
/// </summary>
/// <param name="header">
/// A <see cref="AudioHeader" /> object in which the found
/// header will be stored.
/// </param>
/// <param name="file">
/// A <see cref="TagLib.File" /> object to search.
/// </param>
/// <param name="position">
/// A <see cref="long" /> value specifying the seek position
/// in <paramref name="file" /> at which to start searching.
/// </param>
/// <returns>
/// A <see cref="bool" /> value indicating whether or not a
/// header was found.
/// </returns>
/// <remarks>
/// Searching to the end of the file can be very, very slow
/// especially for corrupt or non-MPEG files. It is
/// recommended to use <see
/// cref="Find(AudioHeader,TagLib.File,long,int)" />
/// instead.
/// </remarks>
public static bool Find(out AudioHeader header,
TagLib.File file, long position)
{
return(Find(out header, file, position, -1));
}
/// <summary>
/// Searches for an audio header in a <see cref="TagLib.File"
/// /> starting at a specified position and searching to the
/// end of the file.
/// </summary>
/// <param name="header">
/// A <see cref="AudioHeader" /> object in which the found
/// header will be stored.
/// </param>
/// <param name="file">
/// A <see cref="TagLib.File" /> object to search.
/// </param>
/// <param name="position">
/// A <see cref="long" /> value specifying the seek position
/// in <paramref name="file" /> at which to start searching.
/// </param>
/// <returns>
/// A <see cref="bool" /> value indicating whether or not a
/// header was found.
/// </returns>
/// <remarks>
/// Searching to the end of the file can be very, very slow
/// especially for corrupt or non-MPEG files. It is
/// recommended to use <see
/// cref="Find(AudioHeader&,TagLib.File,long,int)" />
/// instead.
/// </remarks>
public static bool Find (out AudioHeader header,
TagLib.File file, long position)
{
return Find (out header, file, position, -1);
}
/// <summary>
/// Searches for an audio header in a <see cref="TagLib.File"
/// /> starting at a specified position and searching through
/// a specified number of bytes.
/// </summary>
/// <param name="header">
/// A <see cref="AudioHeader" /> object in which the found
/// header will be stored.
/// </param>
/// <param name="file">
/// A <see cref="TagLib.File" /> object to search.
/// </param>
/// <param name="position">
/// A <see cref="long" /> value specifying the seek position
/// in <paramref name="file" /> at which to start searching.
/// </param>
/// <param name="length">
/// A <see cref="int" /> value specifying the maximum number
/// of bytes to search before aborting.
/// </param>
/// <returns>
/// A <see cref="bool" /> value indicating whether or not a
/// header was found.
/// </returns>
/// <exception cref="ArgumentNullException">
/// <paramref name="file" /> is <see langword="null" />.
/// </exception>
public static bool Find (out AudioHeader header,
TagLib.File file, long position,
int length)
{
if (file == null)
throw new ArgumentNullException ("file");
long end = position + length;
header = AudioHeader.Unknown;
file.Seek (position);
ByteVector buffer = file.ReadBlock (3);
if (buffer.Count < 3)
return false;
do {
file.Seek (position + 3);
buffer = buffer.Mid (buffer.Count - 3);
buffer.Add (file.ReadBlock (
(int) File.BufferSize));
for (int i = 0; i < buffer.Count - 3 &&
(length < 0 || position + i < end); i++)
if (buffer [i] == 0xFF &&
buffer [i + 1] > 0xE0)
try {
header = new AudioHeader (
buffer.Mid (i, 4),
file, position + i);
return true;
} catch (CorruptFileException) {
}
position += File.BufferSize;
} while (buffer.Count > 3 && (length < 0 || position < end));
return false;
}
public static bool Find(out AudioHeader header, TagLib.File file, long position, int length)
{
if (file == null)
{
throw new ArgumentNullException("file");
}
long num = position + length;
header = Unknown;
file.Seek(position);
ByteVector vector = file.ReadBlock(3);
if (vector.Count >= 3)
{
do
{
file.Seek(position + 3L);
vector = vector.Mid(vector.Count - 3);
vector.Add(file.ReadBlock((int) TagLib.File.BufferSize));
for (int i = 0; (i < (vector.Count - 3)) && ((length < 0) || ((position + i) < num)); i++)
{
if ((vector[i] == 0xff) && (vector[i + 1] > 0xe0))
{
try
{
header = new AudioHeader(vector.Mid(i, 4), file, position + i);
return true;
}
catch (CorruptFileException)
{
}
}
}
position += TagLib.File.BufferSize;
}
while ((vector.Count > 3) && ((length < 0) || (position < num)));
}
return false;
}