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MasusderLongerWarrior
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LongerWarrior
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FADPCM decoder (#15)
* FADPCM decoder * Very slight perf improvement Co-Authored-By: LongerWarrior <37636768+longerwarrior@users.noreply.github.com> --------- Co-authored-by: LongerWarrior <37636768+longerwarrior@users.noreply.github.com>
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‎Fmod5Sharp/CodecRebuilders/FmodFadPcmRebuilder.cs‎

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using Fmod5Sharp.FmodTypes;
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using Fmod5Sharp.Util;
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using NAudio.Wave;
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using System;
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using System.Buffers.Binary;
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using System.IO;
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namespace Fmod5Sharp.CodecRebuilders;
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// Credits: https://github.com/vgmstream/vgmstream/blob/master/src/coding/fadpcm_decoder.c
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public class FmodFadPcmRebuilder
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{
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private static readonly short[,] FadpcmCoefs = {
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{ 0, 0 },
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{ 60, 0 },
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{ 122, 60 },
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{ 115, 52 },
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{ 98, 55 },
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{ 0, 0 },
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{ 0, 0 },
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{ 0, 0 }
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};
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public static short[] DecodeFadpcm(FmodSample sample)
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{
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const int FrameSize = 0x8C;
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const int SamplesPerFrame = (FrameSize - 0x0C) * 2;
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ReadOnlySpan<byte> sampleBytes = sample.SampleBytes;
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int numChannels = sample.Metadata.NumChannels;
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int totalFrames = sampleBytes.Length / FrameSize;
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// Total samples across all channels
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short[] outputBuffer = new short[totalFrames * SamplesPerFrame];
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Span<short> outputSpan = outputBuffer;
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int[] hist1 = new int[numChannels];
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int[] hist2 = new int[numChannels];
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for (int f = 0; f < totalFrames; f++)
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{
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int channel = f % numChannels;
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int frameOffset = f * FrameSize;
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ReadOnlySpan<byte> frameSpan = sampleBytes.Slice(frameOffset, FrameSize);
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// Parse Header
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uint coefsLookup = BinaryPrimitives.ReadUInt32LittleEndian(frameSpan[..4]);
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uint shiftsLookup = BinaryPrimitives.ReadUInt32LittleEndian(frameSpan[0x04..]);
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hist1[channel] = BinaryPrimitives.ReadInt16LittleEndian(frameSpan[0x08..]);
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hist2[channel] = BinaryPrimitives.ReadInt16LittleEndian(frameSpan[0x0A..]);
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int frameIndexInChannel = f / numChannels;
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int frameBaseOutIndex = (frameIndexInChannel * SamplesPerFrame * numChannels) + channel;
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// Decode nibbles, grouped in 8 sets of 0x10 * 0x04 * 2
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for (int i = 0; i < 8; i++)
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{
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// Each set has its own coefs/shifts (indexes > 7 are repeat, ex. 0x9 is 0x2)
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int index = (int)((coefsLookup >> (i * 4)) & 0x0F) % 0x07;
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int shift = (int)((shiftsLookup >> (i * 4)) & 0x0F);
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int coef1 = FadpcmCoefs[index, 0];
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int coef2 = FadpcmCoefs[index, 1];
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int finalShift = 22 - shift; // Pre-adjust for 32b sign extend
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for (int j = 0; j < 4; j++)
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{
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uint nibbles = BinaryPrimitives.ReadUInt32LittleEndian(frameSpan[(0x0C + (0x10 * i) + (0x04 * j))..]);
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for (int k = 0; k < 8; k++)
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{
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int sampleValue = (int)((nibbles >> (k * 4)) & 0x0F);
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sampleValue = (sampleValue << 28) >> finalShift; // 32b sign extend + scale
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sampleValue = (sampleValue - (hist2[channel] * coef2) + (hist1[channel] * coef1)) >> 6;
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short finalSample = Utils.ClampToShort(sampleValue);
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int outIndex = frameBaseOutIndex + ((i * 32 + j * 8 + k) * numChannels);
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if (outIndex < outputSpan.Length)
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outputSpan[outIndex] = finalSample;
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hist2[channel] = hist1[channel];
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hist1[channel] = finalSample;
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}
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}
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}
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}
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return outputBuffer;
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}
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public static byte[] Rebuild(FmodSample sample)
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{
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var format = new WaveFormat(sample.Metadata.Frequency, 16, sample.Metadata.NumChannels);
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using var stream = new MemoryStream();
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using (var writer = new WaveFileWriter(stream, format))
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{
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short[] pcmSamples = DecodeFadpcm(sample);
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writer.WriteSamples(pcmSamples, 0, pcmSamples.Length);
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}
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return stream.ToArray();
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}
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}

‎Fmod5Sharp/FmodTypes/FmodAudioType.cs‎

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AT9 = 13,
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XWMA = 14,
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VORBIS = 15,
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FADPCM = 16,
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OPUS = 17
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}
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}

‎Fmod5Sharp/FmodTypes/FmodSample.cs‎

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data = FmodImaAdPcmRebuilder.Rebuild(this);
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fileExtension = "wav";
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return data.Length > 0;
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case FmodAudioType.FADPCM:
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data = FmodFadPcmRebuilder.Rebuild(this);
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fileExtension = "wav";
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return data.Length > 0;
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default:
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data = null;
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fileExtension = null;

‎Fmod5Sharp/Util/FmodAudioTypeExtensions.cs‎

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FmodAudioType.PCM32 => true,
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FmodAudioType.GCADPCM => true,
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FmodAudioType.IMAADPCM => true,
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FmodAudioType.FADPCM => true,
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_ => false
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};
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FmodAudioType.PCM32 => "wav",
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FmodAudioType.GCADPCM => "wav",
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FmodAudioType.IMAADPCM => "wav",
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FmodAudioType.FADPCM => "wav",
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_ => null
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};
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}

‎Fmod5Sharp/Util/Utils.cs‎

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using System;
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using System.Runtime.CompilerServices;
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namespace Fmod5Sharp.Util
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{
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internal static sbyte GetHighNibbleSigned(byte value) => SignedNibbles[(value >> 4) & 0xF];
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internal static sbyte GetLowNibbleSigned(byte value) => SignedNibbles[value & 0xF];
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internal static short Clamp(short val, short min, short max) => Math.Max(Math.Min(val, max), min);
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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internal static short ClampToShort(int value)
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{
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if (value < short.MinValue) return short.MinValue;
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if (value > short.MaxValue) return short.MaxValue;
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return (short)value;
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}
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}
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}

‎NOTICE‎

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This library includes material developed by third-party libraries.
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The attached notices are provided for information only.
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1. License notice for vgmstream (https://github.com/vgmstream/vgmstream/blob/master/COPYING)
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---------------------------------------------------------------------------
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Copyright (c) 2008-2025 Adam Gashlin, Fastelbja, Ronny Elfert, bnnm,
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Christopher Snowhill, NicknineTheEagle, bxaimc,
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Thealexbarney, CyberBotX, et al
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Portions Copyright (c) 2004-2008, Marko Kreen
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Portions Copyright 2001-2007 jagarl / Kazunori Ueno <jagarl@creator.club.ne.jp>
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Portions Copyright (c) 1998, Justin Frankel/Nullsoft Inc.
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Portions Copyright (C) 2006 Nullsoft, Inc.
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Portions Copyright (c) 2005-2007 Paul Hsieh
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Portions Copyright (C) 2000-2004 Leshade Entis, Entis-soft.
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Portions Public Domain originating with Sun Microsystems
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Permission to use, copy, modify, and distribute this software for any
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purpose with or without fee is hereby granted, provided that the above
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copyright notice and this permission notice appear in all copies.
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THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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---------------------------------------------------------------------------

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