public int MbAnalyzeBestUvMode()
{
int bestAlpha = DefaultAlpha;
int smallestAlpha = 0;
int bestMode = 0;
int maxMode = MaxUvMode;
int mode;
this.MakeChroma8Preds();
for (mode = 0; mode < maxMode; ++mode)
{
var histo = new Vp8Histogram();
histo.CollectHistogram(this.YuvIn.AsSpan(UOffEnc), this.YuvP.AsSpan(Vp8Encoding.Vp8UvModeOffsets[mode]), 16, 16 + 4 + 4);
int alpha = histo.GetAlpha();
if (alpha > bestAlpha)
{
bestAlpha = alpha;
}
// The best prediction mode tends to be the one with the smallest alpha.
if (mode == 0 || alpha < smallestAlpha)
{
smallestAlpha = alpha;
bestMode = mode;
}
}
this.SetIntraUvMode(bestMode);
return(bestAlpha);
}
public int MbAnalyzeBestIntra4Mode(int bestAlpha)
{
byte[] modes = new byte[16];
int maxMode = MaxIntra4Mode;
var totalHisto = new Vp8Histogram();
int curHisto = 0;
this.StartI4();
do
{
int mode;
int bestModeAlpha = DefaultAlpha;
var histos = new Vp8Histogram[2];
Span <byte> src = this.YuvIn.AsSpan(YOffEnc + WebpLookupTables.Vp8Scan[this.I4]);
this.MakeIntra4Preds();
for (mode = 0; mode < maxMode; ++mode)
{
histos[curHisto] = new Vp8Histogram();
histos[curHisto].CollectHistogram(src, this.YuvP.AsSpan(Vp8Encoding.Vp8I4ModeOffsets[mode]), 0, 1);
int alpha = histos[curHisto].GetAlpha();
if (alpha > bestModeAlpha)
{
bestModeAlpha = alpha;
modes[this.I4] = (byte)mode;
// Keep track of best histo so far.
curHisto ^= 1;
}
}
// Accumulate best histogram.
histos[curHisto ^ 1].Merge(totalHisto);
}while (this.RotateI4(this.YuvIn.AsSpan(YOffEnc))); // Note: we reuse the original samples for predictors.
int i4Alpha = totalHisto.GetAlpha();
if (i4Alpha > bestAlpha)
{
this.SetIntra4Mode(modes);
bestAlpha = i4Alpha;
}
return(bestAlpha);
}
public int MbAnalyzeBestIntra16Mode()
{
int maxMode = MaxIntra16Mode;
int mode;
int bestAlpha = DefaultAlpha;
int bestMode = 0;
this.MakeLuma16Preds();
for (mode = 0; mode < maxMode; mode++)
{
var histo = new Vp8Histogram();
histo.CollectHistogram(this.YuvIn.AsSpan(YOffEnc), this.YuvP.AsSpan(Vp8Encoding.Vp8I16ModeOffsets[mode]), 0, 16);
int alpha = histo.GetAlpha();
if (alpha > bestAlpha)
{
bestAlpha = alpha;
bestMode = mode;
}
}
this.SetIntra16Mode(bestMode);
return(bestAlpha);
}