/// <summary>
/// Decodes an audio stream through FFmpeg from an encoded file stream.
/// Accepts an optional file name hint to help FFmpeg determine the format of
/// the encoded data.
/// </summary>
/// <param name="stream">the stream to decode</param>
/// <param name="fileName">optional file name hint for FFmpeg</param>
public FFmpegSourceStream(Stream stream, string fileName)
{
sourceStream = stream;
reader = new FFmpegReader(stream, FFmpeg.Type.Audio, fileName);
if (reader.AudioOutputConfig.length == long.MinValue)
{
/*
* length == FFmpeg AV_NOPTS_VALUE
*
* This means that for the opened file/format, there is no length/PTS data
* available, which also makes seeking more or less impossible.
*
* As a workaround, an index could be created to map the frames to the file
* position, and then seek by file position. The index could be created by
* linearly reading through the file (decoding not necessary), and creating
* a mapping of AVPacket.pos to the frame time.
*/
throw new FileNotSeekableException();
}
properties = new AudioProperties(
reader.AudioOutputConfig.format.channels,
reader.AudioOutputConfig.format.sample_rate,
reader.AudioOutputConfig.format.sample_size * 8,
reader.AudioOutputConfig.format.sample_size == 4 ? AudioFormat.IEEE : AudioFormat.LPCM);
readerPosition = 0;
sourceBuffer = new byte[reader.AudioOutputConfig.frame_size *
reader.AudioOutputConfig.format.channels *
reader.AudioOutputConfig.format.sample_size];
sourceBufferPosition = 0;
sourceBufferLength = -1; // -1 means buffer empty, >= 0 means valid buffer data
// determine first PTS to handle cases where it is > 0
try {
Position = 0;
}
catch (InvalidOperationException) {
readerFirstPTS = readerPosition;
readerPosition = 0;
Console.WriteLine("first PTS = " + readerFirstPTS);
}
seekIndexCreated = false;
}
/// <summary>
/// Creates a Wave format proxy file in the same directory and with the same name as the specified file,
/// if no storage directory is specified (i.e. if it is null). If a storage directory is specified, the proxy
/// file will be stored in the specified directory with a hashed file name to avoid name collisions and
/// file overwrites. The story directory option is convenient for the usage of temporary or working directories.
/// </summary>
/// <param name="fileInfo">the file for which a proxy file should be created</param>
/// <param name="storageDirectory">optional directory where the proxy file will be stored, can be null</param>
/// <returns>the FileInfo of the proxy file</returns>
public static FileInfo CreateWaveProxy(FileInfo fileInfo, DirectoryInfo storageDirectory)
{
FileInfo outputFileInfo;
if (storageDirectory == null)
{
// Without a storage directory, store the proxy file beside the original file
outputFileInfo = new FileInfo(fileInfo.FullName + ".ffproxy.wav");
}
else
{
// With a storage directory specified, store the proxy file with a hashed name
// (to avoid name collision / overwrites) in the target directory (e.g. a temp or working directory)
using (var sha256 = SHA256.Create()) {
byte[] hash = sha256.ComputeHash(Encoding.Unicode.GetBytes(fileInfo.FullName));
string hashString = BitConverter.ToString(hash).Replace("-", "").ToLowerInvariant();
outputFileInfo = new FileInfo(Path.Combine(storageDirectory.FullName, hashString + ".ffproxy.wav"));
}
}
if (outputFileInfo.Exists)
{
Console.WriteLine("Proxy already existing, using " + outputFileInfo.Name);
return(outputFileInfo);
}
var reader = new FFmpegReader(fileInfo, FFmpeg.Type.Audio);
var writer = new MemoryWriterStream(new AudioProperties(
reader.AudioOutputConfig.format.channels,
reader.AudioOutputConfig.format.sample_rate,
reader.AudioOutputConfig.format.sample_size * 8,
reader.AudioOutputConfig.format.sample_size == 4 ? AudioFormat.IEEE : AudioFormat.LPCM));
int output_buffer_size = reader.AudioOutputConfig.frame_size * writer.SampleBlockSize;
byte[] output_buffer = new byte[output_buffer_size];
int samplesRead;
long timestamp;
FFmpeg.Type type;
// sequentially read samples from decoder and write it to wav file
while ((samplesRead = reader.ReadFrame(out timestamp, output_buffer, output_buffer_size, out type)) > 0)
{
int bytesRead = samplesRead * writer.SampleBlockSize;
writer.Write(output_buffer, 0, bytesRead);
}
reader.Dispose();
writer.Position = 0;
AudioStreamFactory.WriteToFile(writer, outputFileInfo.FullName);
writer.Close();
return(outputFileInfo);
}
