public static CMp3Frame LoadFromBytes(BufferedData input)
{
var frame = new CMp3Frame();
byte[] headerBytes = new byte[4];
int bytesRead = input.Read(headerBytes, 0, headerBytes.Length);
if (bytesRead == 0)
{
return(null);
}
while (!IsValidHeader(headerBytes, frame))
{
headerBytes[0] = headerBytes[1];
headerBytes[1] = headerBytes[2];
headerBytes[2] = headerBytes[3];
bytesRead = input.Read(headerBytes, 3, 1);
if (bytesRead == 0)
{
return(null);
}
}
int bytesRequired = frame.FrameLength - 4;
frame.RawData = new byte[frame.FrameLength];
Array.Copy(headerBytes, frame.RawData, 4);
bytesRead = input.Read(frame.RawData, 4, bytesRequired);
if (bytesRead == 0)
{
return(null);
}
return(frame);
}
private static CAcmMp3FrameDecompressor CreateFrameDecompressor(CMp3Frame frame)
{
WaveFormat waveFormat = new Mp3WaveFormat(frame.SampleRate, frame.ChannelMode == ChannelMode.Mono ? 1 : 2,
frame.FrameLength, frame.BitRate);
return(new CAcmMp3FrameDecompressor(waveFormat));
}
/// <summary>Reads an CMp3Frame from a stream</summary>
/// <remarks>http://mpgedit.org/mpgedit/mpeg_format/mpeghdr.htm has some good info
/// also see http://www.codeproject.com/KB/audio-video/mpegaudioinfo.aspx
/// </remarks>
/// <returns>A valid MP3 frame, or null if none found</returns>
public static CMp3Frame LoadFromStream(Stream input, bool readData)
{
var frame = new CMp3Frame();
frame.FileOffset = input.Position;
byte[] headerBytes = new byte[4];
int bytesRead = input.Read(headerBytes, 0, headerBytes.Length);
if (bytesRead < headerBytes.Length)
{
// reached end of stream, no more MP3 frames
return(null);
}
while (!IsValidHeader(headerBytes, frame))
{
// shift down by one and try again
headerBytes[0] = headerBytes[1];
headerBytes[1] = headerBytes[2];
headerBytes[2] = headerBytes[3];
bytesRead = input.Read(headerBytes, 3, 1);
if (bytesRead < 1)
{
return(null);
}
frame.FileOffset++;
}
/* no longer read the CRC since we include this in framelengthbytes
* if (this.crcPresent)
* this.crc = reader.ReadInt16();*/
int bytesRequired = frame.FrameLength - 4;
if (readData)
{
frame.RawData = new byte[frame.FrameLength];
Array.Copy(headerBytes, frame.RawData, 4);
bytesRead = input.Read(frame.RawData, 4, bytesRequired);
if (bytesRead < bytesRequired)
{
return(null);
}
}
else
{
// n.b. readData should not be false if input stream does not support seeking
input.Position += bytesRequired;
}
return(frame);
}
/// <summary>
/// Decompresses a frame
/// </summary>
/// <param name="frame">The MP3 frame</param>
/// <param name="dest">destination buffer</param>
/// <param name="destOffset">Offset within destination buffer</param>
/// <returns>Bytes written into destination buffer</returns>
public int DecompressFrame(CMp3Frame frame, byte[] dest, int destOffset)
{
if (frame == null)
{
throw new ArgumentNullException("frame", "You must provide a non-null Mp3Frame to decompress");
}
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(String.Format("Couldn't convert the whole MP3 frame (converted {0}/{1})",
sourceBytesConverted, frame.FrameLength));
}
Array.Copy(conversionStream.DestBuffer, 0, dest, destOffset, converted);
return(converted);
}
private void Mp3Running(object state)
{
CAcmMp3FrameDecompressor decompressor = null;
try
{
do
{
CMp3Frame frame = CMp3Frame.LoadFromBytes(_bufferedData);
if (frame == null)
{
continue;
}
if (decompressor == null)
{
decompressor = CreateFrameDecompressor(frame);
bufferedWaveProvider = new BufferedWaveProvider(decompressor.OutputFormat);
bufferedWaveProvider.BufferDuration = TimeSpan.FromSeconds(20);
}
int decompressed = decompressor.DecompressFrame(frame, buffer, 0);
bufferedWaveProvider.AddSamples(buffer, 0, decompressed);
}while (playbackState != StreamingPlaybackState.Stopped);
}
catch (Exception)
{
}
finally
{
StopPlayback();
if (decompressor != null)
{
decompressor.Dispose();
}
}
}
/// <summary>
/// checks if the four bytes represent a valid header,
/// if they are, will parse the values into CMp3Frame
/// </summary>
private static bool IsValidHeader(byte[] headerBytes, CMp3Frame frame)
{
if ((headerBytes[0] == 0xFF) && ((headerBytes[1] & 0xE0) == 0xE0))
{
// TODO: could do with a bitstream class here
frame.MpegVersion = (MpegVersion)((headerBytes[1] & 0x18) >> 3);
if (frame.MpegVersion == MpegVersion.Reserved)
{
//throw new FormatException("Unsupported MPEG Version");
return(false);
}
frame.MpegLayer = (MpegLayer)((headerBytes[1] & 0x06) >> 1);
if (frame.MpegLayer == MpegLayer.Reserved)
{
return(false);
}
int layerIndex = frame.MpegLayer == MpegLayer.Layer1 ? 0 : frame.MpegLayer == MpegLayer.Layer2 ? 1 : 2;
frame.CrcPresent = (headerBytes[1] & 0x01) == 0x00;
frame.BitRateIndex = (headerBytes[2] & 0xF0) >> 4;
if (frame.BitRateIndex == 15)
{
// invalid index
return(false);
}
int versionIndex = frame.MpegVersion == NAudio.Wave.MpegVersion.Version1 ? 0 : 1;
frame.BitRate = bitRates[versionIndex, layerIndex, frame.BitRateIndex] * 1000;
if (frame.BitRate == 0)
{
return(false);
}
int sampleFrequencyIndex = (headerBytes[2] & 0x0C) >> 2;
if (sampleFrequencyIndex == 3)
{
return(false);
}
if (frame.MpegVersion == MpegVersion.Version1)
{
frame.SampleRate = sampleRatesVersion1[sampleFrequencyIndex];
}
else if (frame.MpegVersion == MpegVersion.Version2)
{
frame.SampleRate = sampleRatesVersion2[sampleFrequencyIndex];
}
else
{
// mpegVersion == MpegVersion.Version25
frame.SampleRate = sampleRatesVersion25[sampleFrequencyIndex];
}
bool padding = (headerBytes[2] & 0x02) == 0x02;
bool privateBit = (headerBytes[2] & 0x01) == 0x01;
frame.ChannelMode = (ChannelMode)((headerBytes[3] & 0xC0) >> 6);
frame.ChannelExtension = (headerBytes[3] & 0x30) >> 4;
if (frame.ChannelExtension != 0 && frame.ChannelMode != ChannelMode.JointStereo)
{
//return false;
}
frame.Copyright = (headerBytes[3] & 0x08) == 0x08;
bool original = (headerBytes[3] & 0x04) == 0x04;
int emphasis = (headerBytes[3] & 0x03);
int nPadding = padding ? 1 : 0;
frame.SampleCount = samplesPerFrame[versionIndex, layerIndex];
int coefficient = frame.SampleCount / 8;
if (frame.MpegLayer == MpegLayer.Layer1)
{
frame.FrameLength = (coefficient * frame.BitRate / frame.SampleRate + nPadding) * 4;
}
else
{
frame.FrameLength = (coefficient * frame.BitRate) / frame.SampleRate + nPadding;
}
if (frame.FrameLength > MaxFrameLength)
{
return(false);
}
return(true);
}
return(false);
}
