private const int DSCALE = 1; // storage descaling, needed to make the error fit byte
public static void PickBestIntra16(Vp8EncIterator it, ref Vp8ModeScore rd, Vp8SegmentInfo[] segmentInfos, Vp8EncProba proba)
{
const int numBlocks = 16;
Vp8SegmentInfo dqm = segmentInfos[it.CurrentMacroBlockInfo.Segment];
int lambda = dqm.LambdaI16;
int tlambda = dqm.TLambda;
Span <byte> src = it.YuvIn.AsSpan(Vp8EncIterator.YOffEnc);
Span <int> scratch = it.Scratch3;
var rdTmp = new Vp8ModeScore();
var res = new Vp8Residual();
Vp8ModeScore rdCur = rdTmp;
Vp8ModeScore rdBest = rd;
int mode;
bool isFlat = IsFlatSource16(src);
rd.ModeI16 = -1;
for (mode = 0; mode < WebpConstants.NumPredModes; ++mode)
{
// Scratch buffer.
Span <byte> tmpDst = it.YuvOut2.AsSpan(Vp8EncIterator.YOffEnc);
rdCur.ModeI16 = mode;
// Reconstruct.
rdCur.Nz = (uint)ReconstructIntra16(it, dqm, rdCur, tmpDst, mode);
// Measure RD-score.
rdCur.D = LossyUtils.Vp8_Sse16X16(src, tmpDst);
rdCur.SD = tlambda != 0 ? Mult8B(tlambda, LossyUtils.Vp8Disto16X16(src, tmpDst, WeightY, scratch)) : 0;
rdCur.H = WebpConstants.Vp8FixedCostsI16[mode];
rdCur.R = it.GetCostLuma16(rdCur, proba, res);
if (isFlat)
{
// Refine the first impression (which was in pixel space).
isFlat = IsFlat(rdCur.YAcLevels, numBlocks, WebpConstants.FlatnessLimitI16);
if (isFlat)
{
// Block is very flat. We put emphasis on the distortion being very low!
rdCur.D *= 2;
rdCur.SD *= 2;
}
}
// Since we always examine Intra16 first, we can overwrite *rd directly.
rdCur.SetRdScore(lambda);
if (mode == 0 || rdCur.Score < rdBest.Score)
{
Vp8ModeScore tmp = rdCur;
rdCur = rdBest;
rdBest = tmp;
it.SwapOut();
}
}
if (rdBest != rd)
{
rd = rdBest;
}
// Finalize score for mode decision.
rd.SetRdScore(dqm.LambdaMode);
it.SetIntra16Mode(rd.ModeI16);
// We have a blocky macroblock (only DCs are non-zero) with fairly high
// distortion, record max delta so we can later adjust the minimal filtering
// strength needed to smooth these blocks out.
if ((rd.Nz & 0x100ffff) == 0x1000000 && rd.D > dqm.MinDisto)
{
dqm.StoreMaxDelta(rd.YDcLevels);
}
}