/// <summary>
/// Sends a pseudo-random sample to replicate white noise.
/// </summary>
private void SendNoiseSample(object state)
{
lock (_audioStreamTimer)
{
int bufferSize = SAMPLE_RATE / 1000 * AUDIO_SAMPLE_PERIOD_MILLISECONDS;
float[] linear = new float[bufferSize];
_signalGenerator.Read(linear, 0, bufferSize);
byte[] encodedSample = new byte[bufferSize];
short[] pcm = linear.Select(x => (short)(x * 32767f)).ToArray();
if (_sendingFormat.FormatCodec == SDPMediaFormatsEnum.G722)
{
_g722Codec.Encode(_g722CodecState, encodedSample, pcm, bufferSize);
}
else
{
for (int index = 0; index < bufferSize; index++)
{
if (_sendingFormat.FormatCodec == SDPMediaFormatsEnum.PCMA)
{
encodedSample[index] = ALawEncoder.LinearToALawSample(pcm[index]);
}
else
{
encodedSample[index] = MuLawEncoder.LinearToMuLawSample(pcm[index]);
}
}
}
SendAudioFrame((uint)bufferSize, (int)_sendingFormat.FormatCodec, encodedSample);
}
}
public byte[] EncodeAudio(short[] pcm, AudioFormat format)
{
if (format.Codec == AudioCodecsEnum.G722)
{
if (_g722Codec == null)
{
_g722Codec = new G722Codec();
_g722CodecState = new G722CodecState(G722_BIT_RATE, G722Flags.None);
}
int outputBufferSize = pcm.Length / 2;
byte[] encodedSample = new byte[outputBufferSize];
int res = _g722Codec.Encode(_g722CodecState, encodedSample, pcm, pcm.Length);
return(encodedSample);
}
else if (format.Codec == AudioCodecsEnum.PCMA)
{
return(pcm.Select(x => ALawEncoder.LinearToALawSample(x)).ToArray());
}
else if (format.Codec == AudioCodecsEnum.PCMU)
{
return(pcm.Select(x => MuLawEncoder.LinearToMuLawSample(x)).ToArray());
}
else if (format.Codec == AudioCodecsEnum.L16)
{
// When netstandard2.1 can be used.
//return MemoryMarshal.Cast<short, byte>(pcm)
// Put on the wire in network byte order (big endian).
return(pcm.SelectMany(x => new byte[] { (byte)(x >> 8), (byte)(x) }).ToArray());
}
else if (format.Codec == AudioCodecsEnum.PCM_S16LE)
{
// Put on the wire as little endian.
return(pcm.SelectMany(x => new byte[] { (byte)(x), (byte)(x >> 8) }).ToArray());
}
else
{
throw new ApplicationException($"Audio format {format.Codec} cannot be encoded.");
}
}