public static bool IsFlacAvailable()
{
IntPtr context = IntPtr.Zero;
try
{
context = LibFLAC.FLAC__stream_decoder_new();
return(context != IntPtr.Zero);
}
catch {
return(false);
}
finally
{
if (context != IntPtr.Zero)
{
LibFLAC.FLAC__stream_decoder_finish(context);
LibFLAC.FLAC__stream_decoder_delete(context);
}
}
}
private void ParseFlac(string path)
{
// reference
// https://github.com/tgsstdio/BirdNest.Audio/blob/c1474db37be323355f6415cdd9011bc7f2550689/NAudioFLAC/Library/FLACFileReader.cs
var context = IntPtr.Zero;
try
{
context = LibFLAC.FLAC__stream_decoder_new();
if (context == IntPtr.Zero)
{
throw new Exception("FLAC open failed");
}
int[] w_buf = null;
int sample_index = 0;
LibFLAC.StreamDecoderWriteStatus Write(IntPtr _, IntPtr frame_ptr, IntPtr buffer_ptr, IntPtr __)
{
var frame = (LibFLAC.FlacFrame)Marshal.PtrToStructure(frame_ptr, typeof(LibFLAC.FlacFrame));
if (w_buf == null)
{
w_buf = new int[frame.Header.BlockSize * ChannelCount];
}
for (var c = 0; c < ChannelCount; ++c)
{
var buf = Marshal.ReadIntPtr(buffer_ptr, c * IntPtr.Size);
Marshal.Copy(buf, w_buf, c * frame.Header.BlockSize, frame.Header.BlockSize);
}
for (int i = 0; i < frame.Header.BlockSize; ++i)
{
for (int c = 0; c < ChannelCount; c++)
{
int sample = w_buf[i + c * frame.Header.BlockSize];
switch (BitsPerSample)
{
case 24:
sample = sample >> 8;
Samples[c][i + sample_index] = (short)sample;
break;
case 16:
Samples[c][i + sample_index] = (short)sample;
break;
default:
break;
}
}
}
sample_index += frame.Header.BlockSize;
return(LibFLAC.StreamDecoderWriteStatus.WriteStatusContinue);
}
void Metadata(IntPtr _, IntPtr metadata_ptr, IntPtr __)
{
var metadata = (LibFLAC.FLACMetaData)Marshal.PtrToStructure(metadata_ptr, typeof(LibFLAC.FLACMetaData));
if (metadata.MetaDataType == LibFLAC.FLACMetaDataType.StreamInfo)
{
var stream_info_mem = GCHandle.Alloc(metadata.Data, GCHandleType.Pinned);
try
{
var stream_info = (LibFLAC.FLACStreamInfo)Marshal.PtrToStructure(stream_info_mem.AddrOfPinnedObject(), typeof(LibFLAC.FLACStreamInfo));
Samples = new List <short[]>();
SampleRate = (uint)stream_info.SampleRate;
var len = (long)(stream_info.TotalSamplesHi << 32) + stream_info.TotalSamplesLo;
for (int c = 0; c < stream_info.Channels; ++c)
{
Samples.Add(new short[len]);
}
ChannelCount = (ushort)stream_info.Channels;
BitsPerSample = (ushort)stream_info.BitsPerSample;
BlockAlign = 4;
AudioFormat = 1;
}
finally
{
stream_info_mem.Free();
}
if (BitsPerSample != 16 && BitsPerSample != 24)
{
throw new Exception("FLAC currently support 16/24sbit only.");
}
}
}
void Error(IntPtr _, LibFLAC.DecodeError status, IntPtr __)
{
throw new Exception("FLAC decode error");
}
var status_code = LibFLAC.FLAC__stream_decoder_init_file(context, path, Write, Metadata, Error, IntPtr.Zero);
if (status_code != 0)
{
throw new Exception($"FLAC open error{status_code}");
}
var result = LibFLAC.FLAC__stream_decoder_process_until_end_of_stream(context);
if (!result)
{
throw new Exception($"FLAC decode process failed");
}
}
finally
{
LibFLAC.FLAC__stream_decoder_finish(context);
LibFLAC.FLAC__stream_decoder_delete(context);
}
}
