/// <summary>
/// Finds the <see cref="VbriHeader"/> header within the <paramref name="firstFrame"/>.
/// </summary>
/// <param name="firstFrame">The first frame.</param>
/// <returns>The VBRI header if found; otherwise, null.</returns>
/// <remarks>
/// The VBRI header is located exactly 32 bytes after the end of the first MPEG audio header in the file.
/// It will compare the first 4 bytes against the <see cref="HeaderIndicator"/>
/// to see if the header contains a <see cref="VbriHeader"/> or not.
/// </remarks>
public static new VbriHeader FindHeader(MpaFrame firstFrame)
{
if (firstFrame == null)
throw new ArgumentNullException("firstFrame");
using (StreamBuffer buffer = new StreamBuffer())
{
byte[] data = firstFrame.ToByteArray();
buffer.Write(data);
// 32 bytes = data indicating silence
const long Offset = MpaFrame.FrameHeaderSize + SilenceDataSize;
buffer.Seek(Offset, SeekOrigin.Begin);
string tagName = buffer.ReadString(4, false, false);
return String.Compare(tagName, HeaderIndicator, StringComparison.OrdinalIgnoreCase) == 0
? new VbriHeader(firstFrame, buffer, Offset)
: null;
}
}
/// <summary>
/// Finds the <see cref="VbriHeader"/> header within the <paramref name="firstFrame"/>.
/// </summary>
/// <param name="firstFrame">The first frame.</param>
/// <returns>The VBRI header if found; otherwise, null.</returns>
/// <remarks>
/// The XING header is located after the side information in Layer III in the first MPEG audio header in the file.
/// It will compare the first 4 bytes against the <see cref="VbrHeaderIndicator"/>
/// to see if the header contains a <see cref="XingHeader"/> or not.
/// </remarks>
public static new XingHeader FindHeader(MpaFrame firstFrame)
{
if (firstFrame == null)
throw new ArgumentNullException("firstFrame");
long offset = MpaFrame.FrameHeaderSize + firstFrame.SideInfoSize;
using (StreamBuffer buffer = new StreamBuffer())
{
byte[] data = firstFrame.ToByteArray();
buffer.Write(data);
buffer.Seek(offset, SeekOrigin.Begin);
string tagName = buffer.ReadString(4, false, false);
if ((String.Compare(tagName, VbrHeaderIndicator, StringComparison.OrdinalIgnoreCase) == 0)
|| (String.Compare(tagName, CbrHeaderIndicator, StringComparison.OrdinalIgnoreCase) == 0))
return new XingHeader(firstFrame, buffer, offset);
}
return null;
}
////------------------------------------------------------------------------------------------------------------------------------
private static ApeItem ReadItem(ApeVersion version, StreamBuffer sb, long maximumItemSize)
{
if (sb == null)
throw new ArgumentNullException("sb");
// Find the item.
long startPosition = sb.Position;
long bytesToSkip = GetBytesUntilNextItem(version, sb, maximumItemSize);
// Not found; return null.
if (bytesToSkip == -1)
return null;
// Move the stream position to the start of the frame.
sb.Position = startPosition + bytesToSkip;
int valueSize = sb.ReadLittleEndianInt32();
if ((valueSize <= 0) || (valueSize > ApeTag.MaxAllowedSize))
return null;
int flags = sb.ReadLittleEndianInt32();
maximumItemSize -= 8;
int itemKeyLengthBytes = 0;
long maximumBytesToRead = maximumItemSize;
if (maximumBytesToRead > 0)
{
for (int y = 0; y < maximumBytesToRead; y++)
{
int character = sb.ReadByte();
if (character == 0x00) // 0x00 byte - string terminator.
break;
itemKeyLengthBytes++;
}
}
// Name
sb.Seek(-(itemKeyLengthBytes + 1), SeekOrigin.Current);
string key = sb.ReadString(itemKeyLengthBytes, Encoding.UTF8);
if ((key.Length < MinKeyLengthCharacters) || (itemKeyLengthBytes > MaxKeyLengthBytes))
return null;
// Skip Item key terminator (0x00 byte)
int keyTerminator = sb.ReadByte();
if (keyTerminator != 0x00)
return null;
ApeItem item = GetItem(version, key, flags);
return item.ReadItem(version, valueSize, sb, maximumItemSize) ? item : null;
}
public void SeekTest()
{
StreamBuffer target = new StreamBuffer();
target.WritePadding(0x00, 1024);
const long Offset = 100;
const SeekOrigin Loc = new SeekOrigin();
const long Expected = 100;
long actual= target.Seek(Offset, Loc);
Assert.AreEqual(Expected, actual);
}
////------------------------------------------------------------------------------------------------------------------------------
/// <summary>
/// Finds a <see cref="LameTag"/> in the given stream.
/// </summary>
/// <param name="firstFrameBuffer">The first frame buffer.</param>
/// <param name="offset">The offset.</param>
/// <returns>The <see cref="LameTag"/> when found; otherwise, null.</returns>
public static LameTag FindTag(StreamBuffer firstFrameBuffer, long offset)
{
if (firstFrameBuffer == null)
throw new ArgumentNullException("firstFrameBuffer");
// If limiting the LAME string to 9 bytes "LAME X.YZu", the extension revision 0 could take 27 bytes and it would still fit a 64 kbit 48kHz frame.
firstFrameBuffer.Seek(offset, SeekOrigin.Begin);
string tagName = firstFrameBuffer.ReadString(4, false, false);
return String.Compare(tagName, "LAME", StringComparison.OrdinalIgnoreCase) == 0 ? new LameTag(firstFrameBuffer) : null;
}
////------------------------------------------------------------------------------------------------------------------------------
/// <summary>
/// Initializes a new instance of the <see cref="LameTag"/> class.
/// </summary>
/// <param name="firstFrameBuffer">The first frame buffer containing a <see cref="LameTag"/>.</param>
public LameTag(StreamBuffer firstFrameBuffer)
{
// string lameTag = "LAME"
firstFrameBuffer.ReadString(4);
float ver;
float.TryParse(firstFrameBuffer.ReadString(4), out ver);
Version = ver;
firstFrameBuffer.Seek(-8, SeekOrigin.Current);
if (Version < 3.90f)
{
// Initial LAME info, 20 bytes for LAME tag. for example, "LAME3.12 (beta 6)"
// LAME prior to 3.90 writes only a 20 byte encoder string.
EncoderVersion = firstFrameBuffer.ReadString(20);
}
else
{
EncoderVersion = firstFrameBuffer.ReadString(9);
// Revision Information Tag + VBR Info
int infoAndVbr = firstFrameBuffer.ReadByte();
// Revision information in 4 MSB
InfoTagRevision = infoAndVbr >> 4;
if (InfoTagRevision == Formats.InfoTagRevision.Reserved)
throw new ArgumentException("InfoTagRevision bit is set to reserved (0xF)");
// VBR info in 4 LSB
VbrMethod = infoAndVbr & 0x0F;
// lowpass information, multiply by 100 to get hz
LowpassFilterValue = firstFrameBuffer.ReadByte() * 100;
// Radio replay gain fields
// Peak signal amplitude
PeakSignalAmplitude = firstFrameBuffer.ReadFloat();
// Radio Replay Gain
RadioReplayGain = firstFrameBuffer.ReadInt16();
// Audiophile Replay Gain
AudiophileReplayGain = firstFrameBuffer.ReadInt16();
// Encoding Flags + ATH type
int encodingFlagsAndAthType = firstFrameBuffer.ReadByte();
// Encoding Flags in 4 MSB
EncodingFlags = encodingFlagsAndAthType >> 4;
// LAME ATH Type in 4 LSB
AthType = encodingFlagsAndAthType & 0x0F;
// If ABR, this will be the specified bitrate
// Otherwise (CBR/VBR), the minimal bitrate (255 means 255 or bigger)
BitRate = firstFrameBuffer.ReadByte();
// the 12 bit values (0-4095) of how many samples were added at start (encoder delay)
// in X and how many 0-samples were padded at the end in Y to complete the last frame.
EncoderDelays = firstFrameBuffer.ReadInt(3);
EncoderDelaySamples = EncoderDelays & 0xFFF;
EncoderDelayPaddingSamples = EncoderDelays >> 12;
////int numberSamplesInOriginalWav = frameCount
Misc = firstFrameBuffer.ReadByte();
// Any mp3 can be amplified by a factor 2 ^ ( x * 0.25) in a lossless manner by a tool like eg. mp3gain
// if done so, this 8-bit field can be used to log such transformation happened so that any given time it can be undone.
Mp3Gain = firstFrameBuffer.ReadByte();
// Preset and surround info
PresetSurroundInfo = firstFrameBuffer.ReadInt16();
// 32 bit integer filed containing the exact length in bytes of the mp3 file originally made by LAME excluded ID3 tag info at the end.
MusicLength = firstFrameBuffer.ReadBigEndianInt32();
// Contains a CRC-16 of the complete mp3 music data as made originally by LAME.
_musicCrc = (short)firstFrameBuffer.ReadBigEndianInt16();
// contains a CRC-16 of the first 190 bytes (0x00 - 0xBD) of the Info header frame.
// This field is calculated at the end, once all other fields are completed.
_infoTagCrc = (short)firstFrameBuffer.ReadBigEndianInt16();
}
}
