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using Ryujinx.Graphics.Nvdec.Vp9.Common;
using System;
using System.Diagnostics;
namespace Ryujinx.Graphics.Nvdec.Vp9.Dsp
{
internal static class Prob
{
public const int MaxProb = 255;
private static byte GetProb(uint num, uint den)
{
Debug.Assert(den != 0);
{
int p = (int)(((ulong)num * 256 + (den >> 1)) / den);
// (p > 255) ? 255 : (p < 1) ? 1 : p;
int clippedProb = p | ((255 - p) >> 23) | (p == 0 ? 1 : 0);
return (byte)clippedProb;
}
}
/* This function assumes prob1 and prob2 are already within [1,255] range. */
public static byte WeightedProb(int prob1, int prob2, int factor)
{
return (byte)BitUtils.RoundPowerOfTwo(prob1 * (256 - factor) + prob2 * factor, 8);
}
// MODE_MV_MAX_UPDATE_FACTOR (128) * count / MODE_MV_COUNT_SAT;
private static readonly uint[] _countToUpdateFactor = {
0, 6, 12, 19, 25, 32, 38, 44, 51, 57, 64,
70, 76, 83, 89, 96, 102, 108, 115, 121, 128,
};
private const int ModeMvCountSat = 20;
public static byte ModeMvMergeProbs(byte preProb, uint ct0, uint ct1)
{
uint den = ct0 + ct1;
if (den == 0)
{
return preProb;
}
else
{
uint count = Math.Min(den, ModeMvCountSat);
uint factor = _countToUpdateFactor[(int)count];
byte prob = GetProb(ct0, den);
return WeightedProb(preProb, prob, (int)factor);
}
}
private static uint TreeMergeProbsImpl(
uint i,
sbyte[] tree,
ReadOnlySpan<byte> preProbs,
ReadOnlySpan<uint> counts,
Span<byte> probs)
{
int l = tree[i];
uint leftCount = (l <= 0) ? counts[-l] : TreeMergeProbsImpl((uint)l, tree, preProbs, counts, probs);
int r = tree[i + 1];
uint rightCount = (r <= 0) ? counts[-r] : TreeMergeProbsImpl((uint)r, tree, preProbs, counts, probs);
probs[(int)(i >> 1)] = ModeMvMergeProbs(preProbs[(int)(i >> 1)], leftCount, rightCount);
return leftCount + rightCount;
}
public static void TreeMergeProbs(sbyte[] tree, ReadOnlySpan<byte> preProbs, ReadOnlySpan<uint> counts, Span<byte> probs)
{
TreeMergeProbsImpl(0, tree, preProbs, counts, probs);
}
}
}
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