/// <summary>
/// Initializes an object that reads informations from an mp3 file and stores them into the given database.
/// </summary>
public Id3SongCreator(ShauniDatabase database)
{
this.database = database;
this.id3v1 = new ID3TagV1();
this.id3v2 = new ID3TagV2();
this.mpegHeader = new MpegHeader();
this.UseNewStandard = false;
this.idwav = new IDWav();
}
public MpegFrame(Stream stream, MP3 mp3)
{
var streamPos = stream.Position;
Header = new MpegHeader(stream);
Data = new UInt8[0];
mp3.bitrate = 0;
if (Header.FrameSync < 0xFFE || Header.LayerId == 0 || Header.BitrateIndex == 0 ||
Header.BitrateIndex == 15 || Header.FrequencyIndex == 3)
{
stream.Position = streamPos;
throw new Exception("MPEG header is invalid!");
}
else
{
if (Header.MpegId == 1)
{
mp3.bitrate = (1U << (Int32)(5U + ((UInt32)Header.BitrateIndex - 1U) / 4U)) +
(((UInt32)Header.BitrateIndex - 1U & 3U) <<
(Int32)(3U + ((UInt32)Header.BitrateIndex - 1U) / 4U));
}
else // MPEG-2
{
Int32 bi = Header.BitrateIndex;
Int32 bil = 4 + Header.BitrateIndex / 4;
mp3.bitrate = (UInt32)(bi < 4
? 8 * bi
: (1 << bil) + ((bi & 3) == 0
? 0
: (bi & 3) == 1
? (1 << bil)
: (bi & 3) == 2
? (1 << bil) + ((1 << bil) >> 1)
: (1 << bil) - ((1 << bil) >> 2)
));
}
}
if (mp3.bitrate != 0)
{
var freq = new UInt16[] { 2205, 2400, 1600 };
mp3.samplingFreq = freq[Header.FrequencyIndex];
if (Header.MpegId == 1) // MPEG-1
{
mp3.samplingFreq <<= 1;
}
mp3.frameSize = (mp3.bitrate * 14400) / mp3.samplingFreq;
if (Header.ChannelMode == 3)
{
mp3.frameSize >>= 1;
}
mp3.frameSize -= 4U + (Header.ProtectionBit == 0 ? 2U : 0U) - Header.PaddingBit;
mp3.frameHeaderOffset = (UInt64)stream.Position - 4UL - (Header.ProtectionBit == 0 ? 2UL : 0UL);
if (stream.Position + mp3.frameSize > stream.Length)
{
throw new Exception("MPEG frame abruptly terminated");
}
else
{
Data = new UInt8[mp3.frameSize];
stream.Read(Data, 0, (Int32)mp3.frameSize);
}
mp3.sumBitrate += mp3.bitrate;
++mp3.framesCount;
}
}
//////////////////////////////////////////////////////////////////////////
// private methods
//////////////////////////////////////////////////////////////////////////
private void Read ()
{
// Since we've likely just looked for the ID3v1 tag, start at the end of the
// file where we're least likely to have to have to move the disk head.
long last = file.LastFrameOffset;
if (last < 0)
{
TagLibDebugger.Debug ("Mpeg.Properties.Read() -- Could not find a valid last MPEG frame in the stream.");
return;
}
file.Seek (last);
MpegHeader last_header = new MpegHeader (file.ReadBlock (4));
long first = file.FirstFrameOffset;
if (first < 0)
{
TagLibDebugger.Debug ("Mpeg.Properties.Read() -- Could not find a valid first MPEG frame in the stream.");
return;
}
if(!last_header.IsValid)
{
long pos = last;
while (pos > first)
{
pos = file.PreviousFrameOffset (pos);
if(pos < 0)
break;
file.Seek (pos);
MpegHeader header = new MpegHeader (file.ReadBlock (4));
if (header.IsValid)
{
last_header = header;
last = pos;
break;
}
}
}
// Now jump back to the front of the file and read what we need from there.
file.Seek (first);
MpegHeader first_header = new MpegHeader (file.ReadBlock (4));
if (!first_header.IsValid || !last_header.IsValid)
{
TagLibDebugger.Debug ("Mpeg.Properties.Read() -- Page headers were invalid.");
return;
}
// Check for a Xing header that will help us in gathering information about a
// VBR stream.
int xing_header_offset = MpegXingHeader.XingHeaderOffset (first_header.Version,
first_header.ChannelMode);
file.Seek (first + xing_header_offset);
MpegXingHeader xing_header = new MpegXingHeader (file.ReadBlock (16));
// Read the length and the bitrate from the Xing header.
if(xing_header.IsValid && first_header.SampleRate > 0 && xing_header.TotalFrames > 0)
{
int [] block_size = {0, 384, 1152, 1152};
double time_per_frame = block_size [first_header.Layer];
time_per_frame = first_header.SampleRate > 0 ? time_per_frame / first_header.SampleRate : 0;
duration = new TimeSpan((int)(time_per_frame * xing_header.TotalFrames) * TimeSpan.TicksPerSecond);
bitrate = (int) (duration > TimeSpan.Zero ? ((xing_header.TotalSize * 8L) / duration.TotalSeconds) / 1000 : 0);
}
// Since there was no valid Xing header found, we hope that we're in a constant
// bitrate file.
// TODO: Make this more robust with audio property detection for VBR without a
// Xing header.
else if (first_header.FrameLength > 0 && first_header.Bitrate > 0)
{
int frames = (int) ((last - first) / first_header.FrameLength + 1);
duration = TimeSpan.FromSeconds ((double) (first_header.FrameLength * frames) / (double) (first_header.Bitrate * 125) + 0.5);
bitrate = first_header.Bitrate;
}
sample_rate = first_header.SampleRate;
channels = first_header.ChannelMode == MpegChannelMode.SingleChannel ? 1 : 2;
version = first_header.Version;
layer = first_header.Layer;
channel_mode = first_header.ChannelMode;
is_copyrighted = first_header.IsCopyrighted;
is_original = first_header.IsOriginal;
}
