private void readAudioDescriptionChunk(BinaryReader source)
{
double sampleRate = StreamUtils.DecodeBEDouble(source.ReadBytes(8)); // aka frames per second
string formatId = Utils.Latin1Encoding.GetString(source.ReadBytes(4));
uint formatFlags = StreamUtils.DecodeBEUInt32(source.ReadBytes(4));
uint bytesPerPacket = StreamUtils.DecodeBEUInt32(source.ReadBytes(4));
uint framesPerPacket = StreamUtils.DecodeBEUInt32(source.ReadBytes(4));
channelsPerFrame = StreamUtils.DecodeBEUInt32(source.ReadBytes(4));
uint bitsPerChannel = StreamUtils.DecodeBEUInt32(source.ReadBytes(4));
this.sampleRate = (uint)Math.Round(sampleRate);
// Compute audio duration
if (bytesPerPacket > 0)
{
double secondsPerPacket = framesPerPacket / sampleRate;
secondsPerByte = secondsPerPacket / bytesPerPacket;
// Duration will be determined using the size of 'data' chunk
}
else
{
secondsPerByte = 0;
isVbr = true;
// Duration will be dertermiend using data from the 'pakt' chunk
}
// Determine audio properties according to the format ID
codecFamily = AudioDataIOFactory.CF_LOSSY;
switch (formatId)
{
case ("lpcm"):
case ("alac"):
codecFamily = AudioDataIOFactory.CF_LOSSLESS;
break;
}
// Determine format
if (formatsMapping.ContainsKey(formatId))
{
containeeAudioFormat = formatsMapping[formatId];
}
else
{
containeeAudioFormat = formatsMapping["none"];
}
}