private OggStream Decode(IList<Page> pages, IList<Packet> packets)
{
VorbisStream vorbis = new VorbisStream(pages, packets);
ParseIdHeder(vorbis, packets[IdHeader]);
ParseCommentHeader(vorbis, packets[CommentHeader]);
vorbis.Duration = GetDuration(pages, packets, vorbis.SampleRate);
return vorbis;
}
private void ParseCommentHeader(VorbisStream vorbis, Packet packet)
{
FileStream.Seek(packet.FileOffset + VorbisHeaderInfo.VendorLengthIndex, SeekOrigin.Begin);
uint vendorLength = BitConverter.ToUInt32(ReadNoSeek(4), 0);
var vendorString = Encoding.UTF8.GetString(ReadNoSeek((int) vendorLength), 0, (int) vendorLength);
uint userCommentListLength = BitConverter.ToUInt32(ReadNoSeek(4), 0);
IList<string> userComments = new List<string>((int) userCommentListLength);
for (uint i = 0; i < userCommentListLength; i++)
{
uint length = BitConverter.ToUInt32(ReadNoSeek(4), 0);
string userComment = Encoding.UTF8.GetString(ReadNoSeek((int) length), 0, (int) length);
userComments.Add(userComment);
}
bool framingFlag = BitConverter.ToBoolean(ReadNoSeek(1), 0);
if (!framingFlag)
throw new InvalidStreamException("Framing flag at the end of the comment header is not set");
vorbis.Comments = new VorbisComments(vendorString, userComments);
}
private void ParseIdHeder(VorbisStream vorbisStream, Packet idHeader)
{
byte[] identificationHeader = Read(idHeader.FileOffset, idHeader.Size);
byte version = identificationHeader[VorbisHeaderInfo.VersionIndex];
byte audioChannels = identificationHeader[VorbisHeaderInfo.AudioChannelsIndex];
uint audioSampleRate = BitConverter.ToUInt32(identificationHeader, VorbisHeaderInfo.AudioSampleRateIndex);
int maxBitrate = BitConverter.ToInt32(identificationHeader, VorbisHeaderInfo.MaximumBitrateIndex);
int nominalBitrate = BitConverter.ToInt32(identificationHeader, VorbisHeaderInfo.NominalBitrateIndex);
int minBitrate = BitConverter.ToInt32(identificationHeader, VorbisHeaderInfo.MinimumBitrateIndex);
uint blockSize0 = (uint) Math.Pow(2, (identificationHeader[VorbisHeaderInfo.BlockSizeIndex] & VorbisHeaderInfo.BlockSize0Mask));
uint blockSize1 = (uint) Math.Pow(2, identificationHeader[VorbisHeaderInfo.BlockSizeIndex] >> 4);
byte framingFlag = identificationHeader[VorbisHeaderInfo.FramingFlagIndex];
vorbisStream.Version = version;
vorbisStream.AudioChannels = audioChannels;
vorbisStream.SampleRate = audioSampleRate;
vorbisStream.BlockSize0 = blockSize0;
vorbisStream.BlockSize1 = blockSize1;
vorbisStream.FramingFlag = framingFlag;
vorbisStream.MaxBitrate = maxBitrate;
vorbisStream.MinBitrate = minBitrate;
vorbisStream.NominalBitrate = nominalBitrate;
}