/// <summary>
/// Decompress a single frame of MP3
/// </summary>
public int DecompressFrame(Mp3Frame frame, byte[] dest, int destOffset)
{
// 1. copy into our DMO's input buffer
inputMediaBuffer.LoadData(frame.RawData, frame.FrameLength);
// 2. Give the input buffer to the DMO to process
mp3Decoder.MediaObject.ProcessInput(0, inputMediaBuffer, DmoInputDataBufferFlags.None, 0, 0);
outputBuffer.MediaBuffer.SetLength(0);
outputBuffer.StatusFlags = DmoOutputDataBufferFlags.None;
// 3. Now ask the DMO for some output data
mp3Decoder.MediaObject.ProcessOutput(DmoProcessOutputFlags.None, 1, new[] {outputBuffer});
if (outputBuffer.Length == 0)
{
Debug.WriteLine("ResamplerDmoStream.Read: No output data available");
return 0;
}
// 5. Now get the data out of the output buffer
outputBuffer.RetrieveData(dest, destOffset);
Debug.Assert(!outputBuffer.MoreDataAvailable, "have not implemented more data available yet");
return outputBuffer.Length;
}
public int DecompressFrame(Mp3Frame frame, byte[] dest, int destOffset)
{
Array.Copy(frame.RawData, conversionStream.SourceBuffer, frame.FrameLength);
int sourceBytesConverted = 0;
int converted = conversionStream.Convert(frame.FrameLength, out sourceBytesConverted);
if (sourceBytesConverted != frame.FrameLength)
{
throw new InvalidOperationException("Couldn't convert the whole MP3 frame");
}
Array.Copy(conversionStream.DestBuffer, 0, dest, destOffset, converted);
return converted;
}
/// <summary>
/// Opens MP3 from a stream rather than a file
/// Will not dispose of this stream itself
/// </summary>
/// <param name="inputStream"></param>
public Mp3FileReader(Stream inputStream)
{
// Calculated as a double to minimize rounding errors
double bitRate;
mp3Stream = inputStream;
id3v2Tag = Id3v2Tag.ReadTag(mp3Stream);
dataStartPosition = mp3Stream.Position;
var mp3Frame = new Mp3Frame(mp3Stream);
sampleRate = mp3Frame.SampleRate;
frameLengthInBytes = mp3Frame.FrameLength;
bitRate = mp3Frame.BitRate;
xingHeader = XingHeader.LoadXingHeader(mp3Frame);
// If the header exists, we can skip over it when decoding the rest of the file
if (xingHeader != null) dataStartPosition = mp3Stream.Position;
mp3DataLength = mp3Stream.Length - dataStartPosition;
// try for an ID3v1 tag as well
mp3Stream.Position = mp3Stream.Length - 128;
var tag = new byte[128];
mp3Stream.Read(tag, 0, 3);
if (tag[0] == 'T' && tag[1] == 'A' && tag[2] == 'G')
{
id3v1Tag = tag;
mp3DataLength -= 128;
}
mp3Stream.Position = dataStartPosition;
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.
bitRate = (mp3DataLength*8.0/TotalSeconds());
mp3Stream.Position = dataStartPosition;
Mp3WaveFormat = new Mp3WaveFormat(sampleRate, mp3Frame.ChannelMode == ChannelMode.Mono ? 1 : 2, frameLengthInBytes,
(int) bitRate);
decompressor = new AcmMp3FrameDecompressor(Mp3WaveFormat); // new DmoMp3FrameDecompressor(this.Mp3WaveFormat);
waveFormat = decompressor.OutputFormat;
bytesPerSample = (decompressor.OutputFormat.BitsPerSample)/8*decompressor.OutputFormat.Channels;
// no MP3 frames have more than 1152 samples in them
// some MP3s I seem to get double
decompressBuffer = new byte[1152*bytesPerSample*2];
}
/// <summary>
/// Reads the next mp3 frame
/// </summary>
/// <returns>Next mp3 frame, or null if EOF</returns>
public Mp3Frame ReadNextFrame(bool readData)
{
if (mp3Stream.Position + frameLengthInBytes <= mp3DataLength + dataStartPosition)
{
var frame = new Mp3Frame(mp3Stream, readData);
tocIndex++;
return frame;
}
return null;
}
/// <summary>
/// Load Xing Header
/// </summary>
/// <param name="frame">Frame</param>
/// <returns>Xing Header</returns>
public static XingHeader LoadXingHeader(Mp3Frame frame)
{
var 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
{
return null;
}
var 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;
}
