// Reference: https://wiki.multimedia.cx/index.php/Microsoft_ADPCM
public ISound Decode(ReadOnlySpan <byte> data, IWaveFormat fmtChunk, MicrosoftAdpcmFormat microsoftAdpcmFormat)
{
var channels = fmtChunk.Channels;
var channelSamplesPerFrame = microsoftAdpcmFormat.SamplesPerBlock;
var buffer = new float[channelSamplesPerFrame];
var frameSize = fmtChunk.BlockAlign;
var max = data.Length / frameSize * frameSize;
var output = Enumerable.Range(0, channels).Select(i => new List <float>()).ToArray();
// Apply coefficients
var coefficients =
new int[Math.Max(MicrosoftAdpcmConstants.DefaultCoefficients.Length, microsoftAdpcmFormat.Coefficients.Length)].AsMemory();
MicrosoftAdpcmConstants.DefaultCoefficients.AsSpan().CopyTo(coefficients.Span);
microsoftAdpcmFormat.Coefficients.AsSpan().CopyTo(coefficients.Span);
for (var offset = 0; offset < max; offset += frameSize)
{
var mem = data.Slice(offset, frameSize);
for (var channel = 0; channel < channels; channel++)
{
DecodeFrame(mem, buffer, channel, channels, coefficients.Span);
output[channel].AddRange(buffer);
}
}
return(new Sound
{
Samples = output.Select(s => new Sample {
Data = s
}).Cast <ISample>().ToList()
});
}
public IRiffContainer Encode(ISound sound, int samplesPerBlock)
{
var sampleRate = sound[NumericData.Rate];
if (sampleRate == null)
{
var sampleRates = sound
.Samples
.Select(s => s[NumericData.Rate])
.Where(r => r != null)
.Distinct()
.ToArray();
sampleRate = sampleRates.SingleOrDefault();
}
if (sampleRate == null)
{
sampleRate = 44100;
}
var channels = sound.Samples.Count;
var byteRate = sampleRate * channels * 2 / 4; //not accurate but not far off
var container = new RiffContainer
{
Format = "WAVE",
Chunks = new List <IRiffChunk>()
};
var extraFormat = new MicrosoftAdpcmFormat
{
Coefficients = MicrosoftAdpcmConstants.DefaultCoefficients,
SamplesPerBlock = 500
};
var format = new RiffFormat
{
Format = 2,
SampleRate = (int)sampleRate,
Channels = channels,
ByteRate = (int)byteRate,
BitsPerSample = 4,
BlockAlign = _microsoftAdpcmEncoder.GetBlockSize(samplesPerBlock, channels),
ExtraData = extraFormat.ToBytes()
};
container.Chunks.Add(_formatEncoder.Encode(format));
container.Chunks.Add(new RiffChunk
{
Id = "data",
Data = _microsoftAdpcmEncoder.Encode(sound, samplesPerBlock)
});
return(container);
}
public ISound Decode(Stream stream)
{
var riff = _riffStreamReader.Read(stream);
if (riff.Format != "WAVE")
{
throw new RhythmCodexException("RIFF type must be WAVE.");
}
var fmt = riff.Chunks.FirstOrDefault(c => c.Id == "fmt ");
if (fmt == null)
{
throw new RhythmCodexException("RIFF must contain the fmt chunk.");
}
var format = _waveFmtDecoder.Decode(fmt);
var data = riff.Chunks.FirstOrDefault(c => c.Id == "data");
if (data == null)
{
throw new RhythmCodexException("RIFF must contain the data chunk.");
}
var result = new Sound
{
[NumericData.Rate] = format.SampleRate,
Samples = new List <ISample>()
};
switch (format.Format)
{
case 0x0001: // raw PCM
{
float[] decoded;
switch (format.BitsPerSample)
{
case 8:
decoded = _pcmDecoder.Decode8Bit(data.Data);
break;
case 16:
decoded = _pcmDecoder.Decode16Bit(data.Data);
break;
case 24:
decoded = _pcmDecoder.Decode24Bit(data.Data);
break;
case 32:
decoded = _pcmDecoder.Decode32Bit(data.Data);
break;
default:
throw new RhythmCodexException("Invalid bits per sample.");
}
foreach (var channel in decoded.Deinterleave(1, format.Channels))
{
result.Samples.Add(new Sample
{
[NumericData.Rate] = format.SampleRate,
Data = channel
});
}
break;
}
case 0x0002: // Microsoft ADPCM
{
var exFormat = new MicrosoftAdpcmFormat(format.ExtraData);
var decoded = _microsoftAdpcmDecoder.Decode(data.Data.AsSpan(), format, exFormat);
foreach (var sample in decoded.Samples)
{
result.Samples.Add(sample);
}
break;
}
case 0x0003: // 32-bit float
{
var decoded = _pcmDecoder.DecodeFloat(data.Data);
foreach (var channel in decoded.Deinterleave(1, format.Channels))
{
result.Samples.Add(new Sample
{
[NumericData.Rate] = format.SampleRate,
Data = channel
});
}
break;
}
case 0x0011: // IMA ADPCM
{
var exFormat = new ImaAdpcmFormat(format.ExtraData);
var decoded = _imaAdpcmDecoder.Decode(new ImaAdpcmChunk
{
Channels = format.Channels,
Rate = format.SampleRate,
Data = data.Data,
ChannelSamplesPerFrame = exFormat.SamplesPerBlock
});
foreach (var sample in decoded.SelectMany(s => s.Samples))
{
result.Samples.Add(sample);
}
break;
}
}
return(result);
}
