private int MbAnalyze(Vp8EncIterator it, int[] alphas, out int bestUvAlpha)
{
it.SetIntra16Mode(0); // default: Intra16, DC_PRED
it.SetSkip(false); // not skipped.
it.SetSegment(0); // default segment, spec-wise.
int bestAlpha;
if (this.method <= WebpEncodingMethod.Level1)
{
bestAlpha = it.FastMbAnalyze(this.quality);
}
else
{
bestAlpha = it.MbAnalyzeBestIntra16Mode();
if (this.method >= WebpEncodingMethod.Level5)
{
// We go and make a fast decision for intra4/intra16.
// It's usually not a good and definitive pick, but helps seeding the stats about level bit-cost.
bestAlpha = it.MbAnalyzeBestIntra4Mode(bestAlpha);
}
}
bestUvAlpha = it.MbAnalyzeBestUvMode();
// Final susceptibility mix.
bestAlpha = ((3 * bestAlpha) + bestUvAlpha + 2) >> 2;
bestAlpha = FinalAlphaValue(bestAlpha);
alphas[bestAlpha]++;
it.CurrentMacroBlockInfo.Alpha = bestAlpha; // For later remapping.
return(bestAlpha); // Mixed susceptibility (not just luma).
}