protected override void ReadStart(long start, ReadStyle propertiesStyle)
{
if (propertiesStyle != ReadStyle.None && !AudioHeader.Find(out first_header, this, start, 0x4000))
{
throw new CorruptFileException("ADTS audio header not found.");
}
}
/// <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("ADTS audio header not found.");
}
}
/// <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] >= 0xF0) // 0xFFF
{
try
{
BitStream bits = new BitStream(buffer.Mid(i, 7).Data);
// 12 bits sync header
bits.ReadInt32(12);
// 1 bit mpeg 2/4
bits.ReadInt32(1);
// 2 bits layer
bits.ReadInt32(2);
// 1 bit protection absent
bits.ReadInt32(1);
// 2 bits profile object type
bits.ReadInt32(2);
// 4 bits sampling frequency index
int samplerateindex = bits.ReadInt32(4);
if (samplerateindex >= sample_rates.Length)
{
return(false);
}
long samplerate = sample_rates[samplerateindex];
// 1 bit private bit
bits.ReadInt32(1);
// 3 bits channel configuration
int channelconfigindex = bits.ReadInt32(3);
if (channelconfigindex >= channels.Length)
{
return(false);
}
// 4 copyright bits
bits.ReadInt32(4);
// 13 bits frame length
long framelength = bits.ReadInt32(13); // double check framelength
if (framelength < 7)
{
return(false);
}
// 11 bits buffer fullness
bits.ReadInt32(11);
// 2 bits number of raw data blocks in frame
int numberofframes = bits.ReadInt32(2) + 1;
long numberofsamples = numberofframes * 1024;
long bitrate = framelength * 8 * samplerate / numberofsamples;
header = new AudioHeader(channels[channelconfigindex],
(int)bitrate,
(int)samplerate,
(int)numberofsamples,
numberofframes);
return(true);
}
catch (CorruptFileException)
{
}
}
}
position += File.BufferSize;
} while (buffer.Count > 3 && (length < 0 || position < end));
return(false);
}
/// <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] >= 0xF0) // 0xFFF
try
{
BitStream bits = new BitStream(buffer.Mid(i, 7).Data);
// 12 bits sync header
bits.ReadInt32(12);
// 1 bit mpeg 2/4
bits.ReadInt32(1);
// 2 bits layer
bits.ReadInt32(2);
// 1 bit protection absent
bits.ReadInt32(1);
// 2 bits profile object type
bits.ReadInt32(2);
// 4 bits sampling frequency index
int samplerateindex = bits.ReadInt32(4);
if(samplerateindex >= sample_rates.Length)
return false;
long samplerate = sample_rates[samplerateindex];
// 1 bit private bit
bits.ReadInt32(1);
// 3 bits channel configuration
int channelconfigindex = bits.ReadInt32(3);
if (channelconfigindex >= channels.Length)
return false;
// 4 copyright bits
bits.ReadInt32(4);
// 13 bits frame length
long framelength = bits.ReadInt32(13); // double check framelength
if (framelength < 7)
return false;
// 11 bits buffer fullness
bits.ReadInt32(11);
// 2 bits number of raw data blocks in frame
int numberofframes = bits.ReadInt32(2) + 1;
long numberofsamples = numberofframes * 1024;
long bitrate = framelength * 8 * samplerate / numberofsamples;
header = new AudioHeader(channels[channelconfigindex],
(int)bitrate,
(int)samplerate,
(int)numberofsamples,
numberofframes);
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] >= 240))
{
bool flag;
try
{
BitStream stream = new BitStream(vector.Mid(i, 7).Data);
stream.ReadInt32(12);
stream.ReadInt32(1);
stream.ReadInt32(2);
stream.ReadInt32(1);
stream.ReadInt32(2);
int index = stream.ReadInt32(4);
if (index >= sample_rates.Length)
{
return false;
}
long num4 = sample_rates[index];
stream.ReadInt32(1);
int num5 = stream.ReadInt32(3);
if (num5 >= channels.Length)
{
return false;
}
stream.ReadInt32(4);
long num6 = stream.ReadInt32(13);
if (num6 < 7L)
{
return false;
}
stream.ReadInt32(11);
int numberofframes = stream.ReadInt32(2) + 1;
long num8 = numberofframes * 0x400;
long num9 = ((num6 * 8L) * num4) / num8;
header = new AudioHeader(channels[num5], (int) num9, (int) num4, (int) num8, numberofframes);
flag = true;
}
catch (CorruptFileException)
{
}
return flag;
}
}
position += TagLib.File.BufferSize;
}
while ((vector.Count > 3) && ((length < 0) || (position < num)));
}
return false;
}
