private static Func <PitchHmmEmission, double> NoteProbability(UtauNote note)
{
if (note == null)
{
throw new ArgumentNullException(nameof(note));
}
if (note.IsRestNote)
{
throw new ArgumentException();
}
// 正規分布
const double stdDev = 0.6;
var mean = note.NoteNumber % 12;
return(e =>
{
if (e.IsSilent)
{
return double.NegativeInfinity;
}
var p = Math.Max(
Math.Max(
NormalDistribution(mean, stdDev, e.NormalizedPitch),
NormalDistribution(mean - 12, stdDev, e.NormalizedPitch)
),
NormalDistribution(mean + 12, stdDev, e.NormalizedPitch)
);
return Math.Log(p);
});
}
/// <summary>
/// <paramref name="restNote"/> を通過するときに無音状態になる確率
/// </summary>
private static double ProbabilityOfNoSoundWhenRestNote(UtauNote restNote)
{
if (!restNote.IsRestNote)
{
throw new ArgumentException();
}
// 長さ 720 程度で 0.65 に到達するくらいの確率
const int maxLength = 720;
const double minProbability = 0.3;
const double maxProbability = 0.65;
return(Math.Min(
minProbability + ((maxProbability - minProbability) / maxLength) * restNote.Length,
maxProbability
));
}
/// <summary>
/// <paramref name="prevNote"/> のあとに無音状態になる確率
/// </summary>
private static double ProbabilityOfNoSoundAfter(UtauNote prevNote)
{
// ノートが長いほど、そのあとは休みがち
const int minLength = 480;
const double minProbability = 0.05;
const double maxProbability = 0.2;
// 短いときはほとんど休まない
if (prevNote.Length <= minLength)
{
return(minProbability);
}
// 長いほど確率が上がり、全音符なら 0.2
return(Math.Min(
minProbability + (prevNote.Length - minLength) * ((maxProbability - minProbability) / (1920 - minLength)),
maxProbability
));
}
public static PitchHmmState CreateNoSoundState(UtauNote reportingNote)
{
return(new PitchHmmState(reportingNote, true));
}
public static PitchHmmState CreateEmittingSoundState(UtauNote reportingNote)
{
return(new PitchHmmState(reportingNote, false));
}
protected PitchHmmState(UtauNote reportingNote, bool isSilentState)
{
this.ReportingNote = reportingNote;
this.IsSilentState = isSilentState;
}
public void InputObservation(PitchHmmEmission observation)
{
var states = this._model.States;
var maxLogProbabilities = new double[states.Count];
for (var i = 0; i < maxLogProbabilities.Length; i++)
{
maxLogProbabilities[i] = double.NegativeInfinity;
}
// 初期状態確率 * 遷移確率 * 生成確率 を計算する
foreach (var(fromStateIndex, stateLogProbability) in this._stateLogProbabilities)
{
foreach (var(toStateIndex, transitionLogProbability) in states[fromStateIndex].LogProbabilitiesByOutgoingStateIndexes)
{
var lp = stateLogProbability + transitionLogProbability + states[toStateIndex].EmissionLogProbability(observation);
if (!(lp <= 0.0))
{
throw new Exception("確率が不正な値になりました。"); // NaN チェックも含めるため not <=
}
if (lp > maxLogProbabilities[toStateIndex])
{
maxLogProbabilities[toStateIndex] = lp;
}
}
}
var stateLogProbabilities = this._stateLogProbabilities;
stateLogProbabilities.Clear();
var logSum = double.NegativeInfinity;
var maxP = double.NegativeInfinity; // 最大の確率
var argmaxP = 0; // 最大の確率のときの状態
for (var stateIndex = 0; stateIndex < maxLogProbabilities.Length; stateIndex++)
{
var lp = maxLogProbabilities[stateIndex];
if (double.IsNegativeInfinity(lp))
{
continue;
}
logSum = Special.LogSum(logSum, lp);
stateLogProbabilities.Add(new KeyValuePair <int, double>(stateIndex, lp));
if (lp > maxP)
{
maxP = lp;
argmaxP = stateIndex;
}
}
if (stateLogProbabilities.Count == 0)
{
throw new Exception("すべての状態の確率が 0 になりました。");
}
// 確率が最も高い状態を現在のノートとして認識
this.CurrentNote = states[argmaxP].Value.ReportingNote;
// 次の計算のために確率を均しておく
// 新しい確率 = 確率 / 確率の合計
for (var i = 0; i < stateLogProbabilities.Count; i++)
{
var(stateIndex, lp) = stateLogProbabilities[i];
stateLogProbabilities[i] = new KeyValuePair <int, double>(stateIndex, lp - logSum);
}
}