private void SetSegmentProbas()
{
int[] p = new int[NumMbSegments];
int n;
for (n = 0; n < this.Mbw * this.Mbh; ++n)
{
Vp8MacroBlockInfo mb = this.MbInfo[n];
++p[mb.Segment];
}
if (this.SegmentHeader.NumSegments > 1)
{
byte[] probas = this.Proba.Segments;
probas[0] = (byte)GetProba(p[0] + p[1], p[2] + p[3]);
probas[1] = (byte)GetProba(p[0], p[1]);
probas[2] = (byte)GetProba(p[2], p[3]);
this.SegmentHeader.UpdateMap = probas[0] != 255 || probas[1] != 255 || probas[2] != 255;
if (!this.SegmentHeader.UpdateMap)
{
this.ResetSegments();
}
this.SegmentHeader.Size = (p[0] * (LossyUtils.Vp8BitCost(0, probas[0]) + LossyUtils.Vp8BitCost(0, probas[1]))) +
(p[1] * (LossyUtils.Vp8BitCost(0, probas[0]) + LossyUtils.Vp8BitCost(1, probas[1]))) +
(p[2] * (LossyUtils.Vp8BitCost(1, probas[0]) + LossyUtils.Vp8BitCost(0, probas[2]))) +
(p[3] * (LossyUtils.Vp8BitCost(1, probas[0]) + LossyUtils.Vp8BitCost(1, probas[2])));
}
else
{
this.SegmentHeader.UpdateMap = false;
this.SegmentHeader.Size = 0;
}
}
public int FinalizeSkipProba(int mbw, int mbh)
{
int nbMbs = mbw * mbh;
int nbEvents = this.NbSkip;
this.SkipProba = (byte)CalcSkipProba(nbEvents, nbMbs);
this.UseSkipProba = this.SkipProba < SkipProbaThreshold;
int size = 256;
if (this.UseSkipProba)
{
size += (nbEvents * LossyUtils.Vp8BitCost(1, this.SkipProba)) + ((nbMbs - nbEvents) * LossyUtils.Vp8BitCost(0, this.SkipProba));
size += 8 * 256; // cost of signaling the skipProba itself.
}
return(size);
}
private static int VariableLevelCost(int level, Span <byte> probas)
{
int pattern = WebpLookupTables.Vp8LevelCodes[level - 1][0];
int bits = WebpLookupTables.Vp8LevelCodes[level - 1][1];
int cost = 0;
for (int i = 2; pattern != 0; i++)
{
if ((pattern & 1) != 0)
{
cost += LossyUtils.Vp8BitCost(bits & 1, probas[i]);
}
bits >>= 1;
pattern >>= 1;
}
return(cost);
}
public int FinalizeTokenProbas()
{
bool hasChanged = false;
int size = 0;
for (int t = 0; t < WebpConstants.NumTypes; ++t)
{
for (int b = 0; b < WebpConstants.NumBands; ++b)
{
for (int c = 0; c < WebpConstants.NumCtx; ++c)
{
for (int p = 0; p < WebpConstants.NumProbas; ++p)
{
uint stats = this.Stats[t][b].Stats[c].Stats[p];
int nb = (int)((stats >> 0) & 0xffff);
int total = (int)((stats >> 16) & 0xffff);
int updateProba = WebpLookupTables.CoeffsUpdateProba[t, b, c, p];
int oldP = WebpLookupTables.DefaultCoeffsProba[t, b, c, p];
int newP = CalcTokenProba(nb, total);
int oldCost = BranchCost(nb, total, oldP) + LossyUtils.Vp8BitCost(0, (byte)updateProba);
int newCost = BranchCost(nb, total, newP) + LossyUtils.Vp8BitCost(1, (byte)updateProba) + (8 * 256);
bool useNewP = oldCost > newCost;
size += LossyUtils.Vp8BitCost(useNewP ? 1 : 0, (byte)updateProba);
if (useNewP)
{
// Only use proba that seem meaningful enough.
this.Coeffs[t][b].Probabilities[c].Probabilities[p] = (byte)newP;
hasChanged |= newP != oldP;
size += 8 * 256;
}
else
{
this.Coeffs[t][b].Probabilities[c].Probabilities[p] = (byte)oldP;
}
}
}
}
}
this.Dirty = hasChanged;
return(size);
}
public void CalculateLevelCosts()
{
if (!this.Dirty)
{
return; // Nothing to do.
}
for (int ctype = 0; ctype < WebpConstants.NumTypes; ++ctype)
{
for (int band = 0; band < WebpConstants.NumBands; ++band)
{
for (int ctx = 0; ctx < WebpConstants.NumCtx; ++ctx)
{
Vp8ProbaArray p = this.Coeffs[ctype][band].Probabilities[ctx];
Vp8CostArray table = this.LevelCost[ctype][band].Costs[ctx];
int cost0 = ctx > 0 ? LossyUtils.Vp8BitCost(1, p.Probabilities[0]) : 0;
int costBase = LossyUtils.Vp8BitCost(1, p.Probabilities[1]) + cost0;
int v;
table.Costs[0] = (ushort)(LossyUtils.Vp8BitCost(0, p.Probabilities[1]) + cost0);
for (v = 1; v <= MaxVariableLevel; ++v)
{
table.Costs[v] = (ushort)(costBase + VariableLevelCost(v, p.Probabilities));
}
// Starting at level 67 and up, the variable part of the cost is actually constant
}
}
for (int n = 0; n < 16; ++n)
{
for (int ctx = 0; ctx < WebpConstants.NumCtx; ++ctx)
{
Vp8CostArray dst = this.RemappedCosts[ctype][n].Costs[ctx];
Vp8CostArray src = this.LevelCost[ctype][WebpConstants.Vp8EncBands[n]].Costs[ctx];
src.Costs.CopyTo(dst.Costs.AsSpan());
}
}
}
this.Dirty = false;
}
// Cost of coding 'nb' 1's and 'total-nb' 0's using 'proba' probability. private static int BranchCost(int nb, int total, int proba) => (nb * LossyUtils.Vp8BitCost(1, (byte)proba)) + ((total - nb) * LossyUtils.Vp8BitCost(0, (byte)proba));