Add ATRAC9 decoder

src/VGAudio.Atrac9/Codecs/Atrac9/Atrac9Config.cs

@@ -0,0 +1,67 @@
+using System.IO;
+using VGAudio.Utilities;
+
+namespace VGAudio.Codecs.Atrac9
+{
+    public class Atrac9Config
+    {
+        public int ChannelCount { get; }
+        public int SampleRate { get; }
+        public int SuperframeSize { get; }
+        public byte[] ConfigData { get; }
+
+        public int SampleRateIndex { get; }
+        public int FrameSamplesPower { get; }
+        public int FrameSamples { get; }
+        public int ChannelConfigIndex { get; }
+        public int FrameSize { get; }
+        public int SuperframeIndex { get; }
+        public int SuperframeSamples { get; }
+        public int FramesPerSuperframe { get; }
+        public bool HighSampleRate { get; }
+        public ChannelConfig ChannelConfig { get; }
+
+        public Atrac9Config(byte[] configData)
+        {
+            if (configData == null || configData.Length != 4)
+            {
+                throw new InvalidDataException("Config data must be 4 bytes long");
+            }
+
+            ReadConfigData(configData, out int a, out int b, out int c, out int d);
+            SampleRateIndex = a;
+            ChannelConfigIndex = b;
+            FrameSize = c;
+            SuperframeIndex = d;
+            ConfigData = configData;
+
+            FramesPerSuperframe = 1 << SuperframeIndex;
+            SuperframeSize = FrameSize << SuperframeIndex;
+            ChannelConfig = Tables.ChannelConfig[ChannelConfigIndex];
+
+            ChannelCount = ChannelConfig.ChannelCount;
+            SampleRate = Tables.SampleRates[SampleRateIndex];
+            HighSampleRate = SampleRateIndex > 7;
+            FrameSamplesPower = Tables.SamplingRateIndexToFrameSamplesPower[SampleRateIndex];
+            FrameSamples = 1 << FrameSamplesPower;
+            SuperframeSamples = FrameSamples * FramesPerSuperframe;
+        }
+
+        private static void ReadConfigData(byte[] configData, out int sampleRateIndex, out int channelConfigIndex, out int frameSize, out int superframeIndex)
+        {
+            var reader = new BitReader(configData);
+
+            int header = reader.ReadInt(8);
+            sampleRateIndex = reader.ReadInt(4);
+            channelConfigIndex = reader.ReadInt(3);
+            int validationBit = reader.ReadInt(1);
+            frameSize = reader.ReadInt(11) + 1;
+            superframeIndex = reader.ReadInt(2);
+
+            if (header != 0xFE || validationBit != 0)
+            {
+                throw new InvalidDataException("ATRAC9 Config Data is invalid");
+            }
+        }
+    }
+}

src/VGAudio.Atrac9/Codecs/Atrac9/Atrac9Decoder.cs

@@ -0,0 +1,97 @@
+using System;
+using VGAudio.Utilities;
+
+namespace VGAudio.Codecs.Atrac9
+{
+    public class Atrac9Decoder
+    {
+        public Atrac9Config Config { get; private set; }
+
+        private Frame Frame { get; set; }
+        private BitReader Reader { get; set; }
+
+        public void Initialize(byte[] configData)
+        {
+            Config = new Atrac9Config(configData);
+            Frame = new Frame(Config);
+            Reader = new BitReader(null);
+        }
+
+        public void Decode(byte[] atrac9Data, short[][] pcmOut)
+        {
+            ValidateBufferLength(pcmOut);
+            Reader.SetBuffer(atrac9Data);
+            DecodeSuperFrame(pcmOut);
+        }
+
+        private void ValidateBufferLength(short[][] buffer)
+        {
+            if (buffer == null || buffer.Length < Config.ChannelCount)
+            {
+                throw new ArgumentException("PCM buffer is too small");
+            }
+
+            for (int i = 0; i < Config.ChannelCount; i++)
+            {
+                if (buffer[i]?.Length < Config.SuperframeSamples)
+                {
+                    throw new ArgumentException("PCM buffer is too small");
+                }
+            }
+        }
+
+        private void DecodeSuperFrame(short[][] pcmOut)
+        {
+            for (int i = 0; i < Config.FramesPerSuperframe; i++)
+            {
+                Frame.FrameIndex = i;
+                DecodeFrame(Reader, Frame);
+                PcmFloatToShort(pcmOut, i * Config.FrameSamples);
+                Reader.AlignPosition(8);
+            }
+        }
+
+        private void PcmFloatToShort(short[][] pcmOut, int start)
+        {
+            int endSample = start + Config.FrameSamples;
+            int channelNum = 0;
+            foreach (Block block in Frame.Blocks)
+            {
+                foreach (Channel channel in block.Channels)
+                {
+                    double[] pcmSrc = channel.Pcm;
+                    short[] pcmDest = pcmOut[channelNum++];
+                    for (int d = 0, s = start; s < endSample; d++, s++)
+                    {
+                        double sample = pcmSrc[d];
+                        // Not using Math.Round because it's ~20x slower on 64-bit
+                        int roundedSample = (int)Math.Floor(sample + 0.5);
+                        pcmDest[s] = Helpers.Clamp16(roundedSample);
+                    }
+                }
+            }
+        }
+
+        private static void DecodeFrame(BitReader reader, Frame frame)
+        {
+            Unpack.UnpackFrame(reader, frame);
+
+            foreach (Block block in frame.Blocks)
+            {
+                Quantization.DequantizeSpectra(block);
+                Stereo.ApplyIntensityStereo(block);
+                Quantization.ScaleSpectrum(block);
+                BandExtension.ApplyBandExtension(block);
+                ImdctBlock(block);
+            }
+        }
+
+        private static void ImdctBlock(Block block)
+        {
+            foreach (Channel channel in block.Channels)
+            {
+                channel.Mdct.RunImdct(channel.Spectra, channel.Pcm);
+            }
+        }
+    }
+}

src/VGAudio.Atrac9/Codecs/Atrac9/Atrac9Parameters.cs

@@ -0,0 +1,9 @@
+
+namespace VGAudio.Codecs.Atrac9
+{
+    public class Atrac9Parameters : CodecParameters
+    {
+        public Atrac9Parameters() { }
+        public Atrac9Parameters(CodecParameters source) : base(source) { }
+    }
+}

src/VGAudio.Atrac9/Codecs/Atrac9/Atrac9Rng.cs

@@ -0,0 +1,33 @@
+namespace VGAudio.Codecs.Atrac9
+{
+    /// <summary>
+    /// An Xorshift RNG used by the ATRAC9 codec
+    /// </summary>
+    internal class Atrac9Rng
+    {
+        private ushort _stateA;
+        private ushort _stateB;
+        private ushort _stateC;
+        private ushort _stateD;
+
+        public Atrac9Rng(ushort seed)
+        {
+            int startValue = 0x4D93 * (seed ^ (seed >> 14));
+
+            _stateA = (ushort)(3 - startValue);
+            _stateB = (ushort)(2 - startValue);
+            _stateC = (ushort)(1 - startValue);
+            _stateD = (ushort)(0 - startValue);
+        }
+
+        public ushort Next()
+        {
+            ushort t = (ushort)(_stateD ^ (_stateD << 5));
+            _stateD = _stateC;
+            _stateC = _stateB;
+            _stateB = _stateA;
+            _stateA = (ushort)(t ^ _stateA ^ ((t ^ (_stateA >> 5)) >> 4));
+            return _stateA;
+        }
+    }
+}

src/VGAudio.Atrac9/Codecs/Atrac9/BandExtension.cs

@@ -0,0 +1,176 @@
+using System;
+using static VGAudio.Codecs.Atrac9.Tables;
+
+namespace VGAudio.Codecs.Atrac9
+{
+    internal static class BandExtension
+    {
+        public static void ApplyBandExtension(Block block)
+        {
+            if (!block.BandExtensionEnabled || !block.HasExtensionData) return;
+
+            foreach (Channel channel in block.Channels)
+            {
+                ApplyBandExtensionChannel(channel);
+            }
+        }
+
+        private static void ApplyBandExtensionChannel(Channel channel)
+        {
+            int groupAUnit = channel.Block.QuantizationUnitCount;
+            int[] scaleFactors = channel.ScaleFactors;
+            double[] spectra = channel.Spectra;
+            double[] scales = channel.BexScales;
+            int[] values = channel.BexValues;
+
+            GetBexBandInfo(out int bandCount, out int groupBUnit, out int groupCUnit, groupAUnit);
+            int totalUnits = Math.Max(groupCUnit, 22);
+
+            int groupABin = QuantUnitToCoeffIndex[groupAUnit];
+            int groupBBin = QuantUnitToCoeffIndex[groupBUnit];
+            int groupCBin = QuantUnitToCoeffIndex[groupCUnit];
+            int totalBins = QuantUnitToCoeffIndex[totalUnits];
+
+            FillHighFrequencies(spectra, groupABin, groupBBin, groupCBin, totalBins);
+
+            switch (channel.BexMode)
+            {
+                case 0:
+                    int bexQuantUnits = totalUnits - groupAUnit;
+
+                    switch (bandCount)
+                    {
+                        case 3:
+                            scales[0] = BexMode0Bands3[0][values[0]];
+                            scales[1] = BexMode0Bands3[1][values[0]];
+                            scales[2] = BexMode0Bands3[2][values[1]];
+                            scales[3] = BexMode0Bands3[3][values[2]];
+                            scales[4] = BexMode0Bands3[4][values[3]];
+                            break;
+                        case 4:
+                            scales[0] = BexMode0Bands4[0][values[0]];
+                            scales[1] = BexMode0Bands4[1][values[0]];
+                            scales[2] = BexMode0Bands4[2][values[1]];
+                            scales[3] = BexMode0Bands4[3][values[2]];
+                            scales[4] = BexMode0Bands4[4][values[3]];
+                            break;
+                        case 5:
+                            scales[0] = BexMode0Bands5[0][values[0]];
+                            scales[1] = BexMode0Bands5[1][values[1]];
+                            scales[2] = BexMode0Bands5[2][values[1]];
+                            break;
+                    }
+
+                    scales[bexQuantUnits - 1] = SpectrumScale[scaleFactors[groupAUnit]];
+
+                    AddNoiseToSpectrum(channel, QuantUnitToCoeffIndex[totalUnits - 1],
+                        QuantUnitToCoeffCount[totalUnits - 1]);
+                    ScaleBexQuantUnits(spectra, scales, groupAUnit, totalUnits);
+                    break;
+                case 1:
+                    for (int i = groupAUnit; i < totalUnits; i++)
+                    {
+                        scales[i - groupAUnit] = SpectrumScale[scaleFactors[i]];
+                    }
+
+                    AddNoiseToSpectrum(channel, groupABin, totalBins - groupABin);
+                    ScaleBexQuantUnits(spectra, scales, groupAUnit, totalUnits);
+                    break;
+                case 2:
+                    double groupAScale2 = BexMode2Scale[values[0]];
+                    double groupBScale2 = BexMode2Scale[values[1]];
+
+                    for (int i = groupABin; i < groupBBin; i++)
+                    {
+                        spectra[i] *= groupAScale2;
+                    }
+
+                    for (int i = groupBBin; i < groupCBin; i++)
+                    {
+                        spectra[i] *= groupBScale2;
+                    }
+                    return;
+                case 3:
+                    double rate = Math.Pow(2, BexMode3Rate[values[1]]);
+                    double scale = BexMode3Initial[values[0]];
+                    for (int i = groupABin; i < totalBins; i++)
+                    {
+                        scale *= rate;
+                        spectra[i] *= scale;
+                    }
+                    return;
+                case 4:
+                    double mult = BexMode4Multiplier[values[0]];
+                    double groupAScale4 = 0.7079468 * mult;
+                    double groupBScale4 = 0.5011902 * mult;
+                    double groupCScale4 = 0.3548279 * mult;
+
+                    for (int i = groupABin; i < groupBBin; i++)
+                    {
+                        spectra[i] *= groupAScale4;
+                    }
+
+                    for (int i = groupBBin; i < groupCBin; i++)
+                    {
+                        spectra[i] *= groupBScale4;
+                    }
+
+                    for (int i = groupCBin; i < totalBins; i++)
+                    {
+                        spectra[i] *= groupCScale4;
+                    }
+                    return;
+            }
+        }
+
+        private static void ScaleBexQuantUnits(double[] spectra, double[] scales, int startUnit, int totalUnits)
+        {
+            for (int i = startUnit; i < totalUnits; i++)
+            {
+                for (int k = QuantUnitToCoeffIndex[i]; k < QuantUnitToCoeffIndex[i + 1]; k++)
+                {
+                    spectra[k] *= scales[i - startUnit];
+                }
+            }
+        }
+
+        private static void FillHighFrequencies(double[] spectra, int groupABin, int groupBBin, int groupCBin, int totalBins)
+        {
+            for (int i = 0; i < groupBBin - groupABin; i++)
+            {
+                spectra[groupABin + i] = spectra[groupABin - i - 1];
+            }
+
+            for (int i = 0; i < groupCBin - groupBBin; i++)
+            {
+                spectra[groupBBin + i] = spectra[groupBBin - i - 1];
+            }
+
+            for (int i = 0; i < totalBins - groupCBin; i++)
+            {
+                spectra[groupCBin + i] = spectra[groupCBin - i - 1];
+            }
+        }
+
+        private static void AddNoiseToSpectrum(Channel channel, int index, int count)
+        {
+            if (channel.Rng == null)
+            {
+                int[] sf = channel.ScaleFactors;
+                ushort seed = (ushort)(543 * (sf[8] + sf[12] + sf[15] + 1));
+                channel.Rng = new Atrac9Rng(seed);
+            }
+            for (int i = 0; i < count; i++)
+            {
+                channel.Spectra[i + index] = channel.Rng.Next() / 65535.0 * 2.0 - 1.0;
+            }
+        }
+
+        public static void GetBexBandInfo(out int bandCount, out int groupAUnit, out int groupBUnit, int quantUnits)
+        {
+            groupAUnit = BexGroupInfo[quantUnits - 13][0];
+            groupBUnit = BexGroupInfo[quantUnits - 13][1];
+            bandCount = BexGroupInfo[quantUnits - 13][2];
+        }
+    }
+}