private Mp3FileReader(Stream inputStream, FrameDecompressorBuilder frameDecompressorBuilder, bool ownInputStream)
{
if (inputStream == null)
{
throw new ArgumentNullException(nameof(inputStream));
}
if (frameDecompressorBuilder == null)
{
throw new ArgumentNullException(nameof(frameDecompressorBuilder));
}
this.ownInputStream = ownInputStream;
try
{
mp3Stream = inputStream;
Id3v2Tag = Id3v2Tag.ReadTag(mp3Stream);
dataStartPosition = mp3Stream.Position;
var firstFrame = Mp3Frame.LoadFromStream(mp3Stream);
if (firstFrame == null)
{
throw new InvalidDataException("Invalid MP3 file - no MP3 Frames Detected");
}
double bitRate = firstFrame.BitRate;
xingHeader = XingHeader.LoadXingHeader(firstFrame);
// If the header exists, we can skip over it when decoding the rest of the file
if (xingHeader != null)
{
dataStartPosition = mp3Stream.Position;
}
// workaround for a longstanding issue with some files failing to load
// because they report a spurious sample rate change
var secondFrame = Mp3Frame.LoadFromStream(mp3Stream);
if (secondFrame != null &&
(secondFrame.SampleRate != firstFrame.SampleRate ||
secondFrame.ChannelMode != firstFrame.ChannelMode))
{
// assume that the first frame was some kind of VBR/LAME header that we failed to recognise properly
dataStartPosition = secondFrame.FileOffset;
// forget about the first frame, the second one is the first one we really care about
firstFrame = secondFrame;
}
mp3DataLength = mp3Stream.Length - dataStartPosition;
// try for an ID3v1 tag as well
mp3Stream.Position = mp3Stream.Length - 128;
byte[] tag = new byte[128];
mp3Stream.Read(tag, 0, 128);
if (tag[0] == 'T' && tag[1] == 'A' && tag[2] == 'G')
{
Id3v1Tag = tag;
mp3DataLength -= 128;
}
mp3Stream.Position = dataStartPosition;
// create a temporary MP3 format before we know the real bitrate
Mp3WaveFormat = new Mp3WaveFormat(firstFrame.SampleRate,
firstFrame.ChannelMode == ChannelMode.Mono ? 1 : 2, firstFrame.FrameLength, (int)bitRate);
CreateTableOfContents();
tocIndex = 0;
// [Bit rate in Kilobits/sec] = [Length in kbits] / [time in seconds]
// = [Length in bits ] / [time in milliseconds]
// Note: in audio, 1 kilobit = 1000 bits.
// Calculated as a double to minimize rounding errors
bitRate = (mp3DataLength * 8.0 / TotalSeconds());
mp3Stream.Position = dataStartPosition;
// now we know the real bitrate we can create an accurate MP3 WaveFormat
Mp3WaveFormat = new Mp3WaveFormat(firstFrame.SampleRate,
firstFrame.ChannelMode == ChannelMode.Mono ? 1 : 2, firstFrame.FrameLength, (int)bitRate);
decompressor = frameDecompressorBuilder(Mp3WaveFormat);
waveFormat = decompressor.OutputFormat;
bytesPerSample = (decompressor.OutputFormat.BitsPerSample) / 8 * decompressor.OutputFormat.Channels;
// no MP3 frames have more than 1152 samples in them
bytesPerDecodedFrame = 1152 * bytesPerSample;
// some MP3s I seem to get double
decompressBuffer = new byte[bytesPerDecodedFrame * 2];
}
catch (Exception)
{
if (ownInputStream)
{
inputStream.Dispose();
}
throw;
}
}
/// <summary>
/// Load Xing Header
/// </summary>
/// <param name="frame">Frame</param>
/// <returns>Xing Header</returns>
public static XingHeader LoadXingHeader(Mp3Frame frame)
{
XingHeader xingHeader = new XingHeader();
xingHeader.frame = frame;
int offset = 0;
if (frame.MpegVersion == MpegVersion.Version1)
{
if (frame.ChannelMode != ChannelMode.Mono)
{
offset = 32 + 4;
}
else
{
offset = 17 + 4;
}
}
else if (frame.MpegVersion == MpegVersion.Version2)
{
if (frame.ChannelMode != ChannelMode.Mono)
{
offset = 17 + 4;
}
else
{
offset = 9 + 4;
}
}
else
{
return(null);
// throw new FormatException("Unsupported MPEG Version");
}
if ((frame.RawData[offset + 0] == 'X') &&
(frame.RawData[offset + 1] == 'i') &&
(frame.RawData[offset + 2] == 'n') &&
(frame.RawData[offset + 3] == 'g'))
{
xingHeader.startOffset = offset;
offset += 4;
}
else if ((frame.RawData[offset + 0] == 'I') &&
(frame.RawData[offset + 1] == 'n') &&
(frame.RawData[offset + 2] == 'f') &&
(frame.RawData[offset + 3] == 'o'))
{
xingHeader.startOffset = offset;
offset += 4;
}
else
{
return(null);
}
XingHeaderOptions flags = (XingHeaderOptions)ReadBigEndian(frame.RawData, offset);
offset += 4;
if ((flags & XingHeaderOptions.Frames) != 0)
{
xingHeader.framesOffset = offset;
offset += 4;
}
if ((flags & XingHeaderOptions.Bytes) != 0)
{
xingHeader.bytesOffset = offset;
offset += 4;
}
if ((flags & XingHeaderOptions.Toc) != 0)
{
xingHeader.tocOffset = offset;
offset += 100;
}
if ((flags & XingHeaderOptions.VbrScale) != 0)
{
xingHeader.vbrScale = ReadBigEndian(frame.RawData, offset);
offset += 4;
}
xingHeader.endOffset = offset;
return(xingHeader);
}
