/// <summary>
/// Generate a precise equalizer setting to flatten the processed response of
/// <see cref="GraphUtils.SmoothGraph(float[], float, float, float)"/>.
/// </summary>
/// <param name="graph">Graph to equalize, a pre-applied smoothing
/// (<see cref="GraphUtils.SmoothGraph(float[], float, float, float)"/> is strongly recommended</param>
/// <param name="startFreq">Frequency at the beginning of the graph</param>
/// <param name="endFreq">Frequency at the end of the graph</param>
/// <param name="targetCurve">Match the frequency response to this EQ curve</param>
/// <param name="targetGain">Target EQ level</param>
/// <param name="maxGain">Maximum gain of any generated band</param>
public static Equalizer AutoCorrectGraph(float[] graph, double startFreq, double endFreq, EQCurve targetCurve,
float targetGain, float maxGain = 6)
{
List <Band> bands = new List <Band>();
double startPow = Math.Log10(startFreq), endPow = Math.Log10(endFreq), powRange = (endPow - startPow) / graph.Length;
List <int> windowEdges = new List <int>(new int[] { 0 });
for (int sample = 1, end = graph.Length - 1; sample < end; ++sample)
{
if ((graph[sample - 1] < graph[sample] && graph[sample + 1] > graph[sample]) ||
(graph[sample - 1] > graph[sample] && graph[sample + 1] < graph[sample]))
{
windowEdges.Add(sample);
}
}
float[] refGain = targetCurve.GenerateLogCurve(startFreq, endFreq, graph.Length, targetGain);
for (int sample = 0, end = windowEdges.Count - 1; sample < end; ++sample)
{
int windowPos = windowEdges[sample];
if (graph[windowPos] > refGain[windowPos] - maxGain)
{
bands.Add(new Band((float)Math.Pow(10, startPow + powRange * windowPos), refGain[windowPos] - graph[windowPos]));
}
}
return(new Equalizer(bands));
}
/// <summary>
/// Generate an equalizer setting to flatten the processed response of
/// <see cref="GraphUtils.SmoothGraph(float[], float, float, float)"/>.
/// </summary>
/// <param name="graph">Graph to equalize, a pre-applied smoothing
/// (<see cref="GraphUtils.SmoothGraph(float[], float, float, float)"/> is strongly recommended</param>
/// <param name="startFreq">Frequency at the beginning of the graph</param>
/// <param name="endFreq">Frequency at the end of the graph</param>
/// <param name="targetCurve">Match the frequency response to this EQ curve</param>
/// <param name="resolution">Band diversity in octaves</param>
/// <param name="targetGain">Target EQ level</param>
/// <param name="maxGain">Maximum gain of any generated band</param>
public static Equalizer CorrectGraph(float[] graph, double startFreq, double endFreq, EQCurve targetCurve, float targetGain,
double resolution = 1 / 3f, float maxGain = 6)
{
List <Band> bands = new List <Band>();
double startPow = Math.Log10(startFreq), powRange = (Math.Log10(endFreq) - startPow) / graph.Length,
octaveRange = Math.Log(endFreq, 2) - Math.Log(startFreq, 2);
int windowSize = graph.Length / (int)(octaveRange / resolution + 1), windowEdge = windowSize / 2;
float[] refGain = targetCurve.GenerateLogCurve(startFreq, endFreq, graph.Length);
for (int pos = graph.Length - 1; pos >= 0; pos -= windowSize)
{
float centerFreq = (float)Math.Pow(10, startPow + powRange * pos), average = 0;
int start = Math.Max(pos - windowEdge, 0), end = Math.Min(pos + windowEdge, graph.Length);
for (int sample = start; sample < end; ++sample)
{
average += graph[sample];
}
float addition = refGain[pos] + targetGain - average / (end - start);
if (addition <= maxGain)
{
bands.Add(new Band(centerFreq, addition));
}
}
bands.Reverse();
return(new Equalizer(bands));
}