private bool IsCorrectHeader(Packet headerPacket, byte headerType)
{
byte[] header = Read(headerPacket.FileOffset, VorbisHeaderInfo.PacketHeaderSize);
if (header[VorbisHeaderInfo.HeaderTypeIndex] != headerType)
return false;
string magicSeq = Encoding.ASCII.GetString(header, VorbisHeaderInfo.MagicSeqIndex, VorbisHeaderInfo.MagicSeqSize);
if (magicSeq != VorbisHeaderInfo.MagicSeq)
return false;
return true;
}
private bool IsVorbisStream(Packet idHeader, Packet commentHeader, Packet setupHeader)
{
if (idHeader.Size < VorbisHeaderInfo.PacketHeaderSize)
return false;
if (commentHeader.Size < VorbisHeaderInfo.PacketHeaderSize)
return false;
if (setupHeader.Size < VorbisHeaderInfo.PacketHeaderSize)
return false;
return IsCorrectHeader(idHeader, VorbisHeaderInfo.IdHeaderType) &&
IsCorrectHeader(commentHeader, VorbisHeaderInfo.CommentHeaderType) &&
IsCorrectHeader(setupHeader, VorbisHeaderInfo.SetupHeaderType);
}
public IEnumerable<Packet> ReadPackets(IEnumerable<Page> pages)
{
if (pages == null) throw new ArgumentNullException("pages");
long fileOffset = 0;
int size = 0;
int firstPage = 0;
int pageIndex = 0;
int numberOfSegments = 0;
bool hasPacket = false;
foreach (var page in pages)
{
//if the previous page had unfinished packet, this page must be marked as continuation
if (hasPacket && page.PageType != PageType.Continuation)
throw new InvalidStreamException("Packet didn't finish on previous page, but next page is not marked as Continuation");
foreach (var segment in page.Segments)
{
//start new packet
if (!hasPacket)
{
fileOffset = segment.FileOffset;
firstPage = pageIndex;
hasPacket = true;
}
numberOfSegments++;
size += segment.Size;
//packet spans across several segments
if (segment.Size == ExtendedSegmentSize) continue;
Packet p = new Packet(fileOffset, size, firstPage, numberOfSegments);
yield return p;
//reset values
size = 0;
fileOffset = 0;
hasPacket = false;
numberOfSegments = 0;
}
pageIndex++;
}
yield break;
}
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;
}
