textures: Reintroduce CPU ASTC decoder

Users may want to fall back to the CPU ASTC texture decoder due to hangs
and crashes that may be caused by keeping the GPU under compute heavy
loads for extended periods of time. This is especially the case in games
such as Astral Chain which make extensive use of ASTC textures.

4 files changed, 1592 insertions, 2 deletions

diff --git a/src/video_core/CMakeLists.txt b/src/video_core/CMakeLists.txt
index 47190c464..f9454bbaa 100644
--- a/src/video_core/CMakeLists.txt
+++ b/src/video_core/CMakeLists.txt
@@ -237,6 +237,7 @@ add_library(video_core STATIC
     texture_cache/util.cpp
     texture_cache/util.h
     textures/astc.h
+    textures/astc.cpp
     textures/decoders.cpp
     textures/decoders.h
     textures/texture.cpp
diff --git a/src/video_core/texture_cache/util.cpp b/src/video_core/texture_cache/util.cpp
index 906604a39..0d3e0804f 100644
--- a/src/video_core/texture_cache/util.cpp
+++ b/src/video_core/texture_cache/util.cpp
@@ -47,6 +47,7 @@
 #include "video_core/texture_cache/formatter.h"
 #include "video_core/texture_cache/samples_helper.h"
 #include "video_core/texture_cache/util.h"
+#include "video_core/textures/astc.h"
 #include "video_core/textures/decoders.h"
 
 namespace VideoCommon {
@@ -884,8 +885,16 @@ void ConvertImage(std::span<const u8> input, const ImageInfo& info, std::span<u8
         ASSERT(copy.image_extent == mip_size);
         ASSERT(copy.buffer_row_length == Common::AlignUp(mip_size.width, tile_size.width));
         ASSERT(copy.buffer_image_height == Common::AlignUp(mip_size.height, tile_size.height));
-        DecompressBC4(input.subspan(copy.buffer_offset), copy.image_extent,
-                      output.subspan(output_offset));
+        if (IsPixelFormatASTC(info.format)) {
+            ASSERT(copy.image_extent.depth == 1);
+            Tegra::Texture::ASTC::Decompress(input.subspan(copy.buffer_offset),
+                                             copy.image_extent.width, copy.image_extent.height,
+                                             copy.image_subresource.num_layers, tile_size.width,
+                                             tile_size.height, output.subspan(output_offset));
+        } else {
+            DecompressBC4(input.subspan(copy.buffer_offset), copy.image_extent,
+                          output.subspan(output_offset));
+        }
         copy.buffer_offset = output_offset;
         copy.buffer_row_length = mip_size.width;
         copy.buffer_image_height = mip_size.height;
diff --git a/src/video_core/textures/astc.cpp b/src/video_core/textures/astc.cpp
new file mode 100644
index 000000000..6079aa709
--- /dev/null
+++ b/src/video_core/textures/astc.cpp
@@ -0,0 +1,1577 @@
+// Copyright 2016 The University of North Carolina at Chapel Hill
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Please send all BUG REPORTS to <pavel@cs.unc.edu>.
+// <http://gamma.cs.unc.edu/FasTC/>
+
+#include <algorithm>
+#include <cassert>
+#include <cstring>
+#include <span>
+#include <vector>
+
+#include <boost/container/static_vector.hpp>
+
+#include "common/common_types.h"
+#include "video_core/textures/astc.h"
+
+class InputBitStream {
+public:
+    constexpr explicit InputBitStream(std::span<const u8> data, size_t start_offset = 0)
+        : cur_byte{data.data()}, total_bits{data.size()}, next_bit{start_offset % 8} {}
+
+    constexpr size_t GetBitsRead() const {
+        return bits_read;
+    }
+
+    constexpr bool ReadBit() {
+        if (bits_read >= total_bits * 8) {
+            return 0;
+        }
+        const bool bit = ((*cur_byte >> next_bit) & 1) != 0;
+        ++next_bit;
+        while (next_bit >= 8) {
+            next_bit -= 8;
+            ++cur_byte;
+        }
+        ++bits_read;
+        return bit;
+    }
+
+    constexpr u32 ReadBits(std::size_t nBits) {
+        u32 ret = 0;
+        for (std::size_t i = 0; i < nBits; ++i) {
+            ret |= (ReadBit() & 1) << i;
+        }
+        return ret;
+    }
+
+    template <std::size_t nBits>
+    constexpr u32 ReadBits() {
+        u32 ret = 0;
+        for (std::size_t i = 0; i < nBits; ++i) {
+            ret |= (ReadBit() & 1) << i;
+        }
+        return ret;
+    }
+
+private:
+    const u8* cur_byte;
+    size_t total_bits = 0;
+    size_t next_bit = 0;
+    size_t bits_read = 0;
+};
+
+class OutputBitStream {
+public:
+    constexpr explicit OutputBitStream(u8* ptr, std::size_t bits = 0, std::size_t start_offset = 0)
+        : cur_byte{ptr}, num_bits{bits}, next_bit{start_offset % 8} {}
+
+    constexpr std::size_t GetBitsWritten() const {
+        return bits_written;
+    }
+
+    constexpr void WriteBitsR(u32 val, u32 nBits) {
+        for (u32 i = 0; i < nBits; i++) {
+            WriteBit((val >> (nBits - i - 1)) & 1);
+        }
+    }
+
+    constexpr void WriteBits(u32 val, u32 nBits) {
+        for (u32 i = 0; i < nBits; i++) {
+            WriteBit((val >> i) & 1);
+        }
+    }
+
+private:
+    constexpr void WriteBit(bool b) {
+        if (bits_written >= num_bits) {
+            return;
+        }
+
+        const u32 mask = 1 << next_bit++;
+
+        // clear the bit
+        *cur_byte &= static_cast<u8>(~mask);
+
+        // Write the bit, if necessary
+        if (b)
+            *cur_byte |= static_cast<u8>(mask);
+
+        // Next byte?
+        if (next_bit >= 8) {
+            cur_byte += 1;
+            next_bit = 0;
+        }
+    }
+
+    u8* cur_byte;
+    std::size_t num_bits;
+    std::size_t bits_written = 0;
+    std::size_t next_bit = 0;
+};
+
+template <typename IntType>
+class Bits {
+public:
+    explicit Bits(const IntType& v) : m_Bits(v) {}
+
+    Bits(const Bits&) = delete;
+    Bits& operator=(const Bits&) = delete;
+
+    u8 operator[](u32 bitPos) const {
+        return static_cast<u8>((m_Bits >> bitPos) & 1);
+    }
+
+    IntType operator()(u32 start, u32 end) const {
+        if (start == end) {
+            return (*this)[start];
+        } else if (start > end) {
+            u32 t = start;
+            start = end;
+            end = t;
+        }
+
+        u64 mask = (1 << (end - start + 1)) - 1;
+        return (m_Bits >> start) & static_cast<IntType>(mask);
+    }
+
+private:
+    const IntType& m_Bits;
+};
+
+namespace Tegra::Texture::ASTC {
+using IntegerEncodedVector = boost::container::static_vector<
+    IntegerEncodedValue, 256,
+    boost::container::static_vector_options<
+        boost::container::inplace_alignment<alignof(IntegerEncodedValue)>,
+        boost::container::throw_on_overflow<false>>::type>;
+
+static void DecodeTritBlock(InputBitStream& bits, IntegerEncodedVector& result, u32 nBitsPerValue) {
+    // Implement the algorithm in section C.2.12
+    std::array<u32, 5> m;
+    std::array<u32, 5> t;
+    u32 T;
+
+    // Read the trit encoded block according to
+    // table C.2.14
+    m[0] = bits.ReadBits(nBitsPerValue);
+    T = bits.ReadBits<2>();
+    m[1] = bits.ReadBits(nBitsPerValue);
+    T |= bits.ReadBits<2>() << 2;
+    m[2] = bits.ReadBits(nBitsPerValue);
+    T |= bits.ReadBit() << 4;
+    m[3] = bits.ReadBits(nBitsPerValue);
+    T |= bits.ReadBits<2>() << 5;
+    m[4] = bits.ReadBits(nBitsPerValue);
+    T |= bits.ReadBit() << 7;
+
+    u32 C = 0;
+
+    Bits<u32> Tb(T);
+    if (Tb(2, 4) == 7) {
+        C = (Tb(5, 7) << 2) | Tb(0, 1);
+        t[4] = t[3] = 2;
+    } else {
+        C = Tb(0, 4);
+        if (Tb(5, 6) == 3) {
+            t[4] = 2;
+            t[3] = Tb[7];
+        } else {
+            t[4] = Tb[7];
+            t[3] = Tb(5, 6);
+        }
+    }
+
+    Bits<u32> Cb(C);
+    if (Cb(0, 1) == 3) {
+        t[2] = 2;
+        t[1] = Cb[4];
+        t[0] = (Cb[3] << 1) | (Cb[2] & ~Cb[3]);
+    } else if (Cb(2, 3) == 3) {
+        t[2] = 2;
+        t[1] = 2;
+        t[0] = Cb(0, 1);
+    } else {
+        t[2] = Cb[4];
+        t[1] = Cb(2, 3);
+        t[0] = (Cb[1] << 1) | (Cb[0] & ~Cb[1]);
+    }
+
+    for (std::size_t i = 0; i < 5; ++i) {
+        IntegerEncodedValue& val = result.emplace_back(IntegerEncoding::Trit, nBitsPerValue);
+        val.bit_value = m[i];
+        val.trit_value = t[i];
+    }
+}
+
+static void DecodeQuintBlock(InputBitStream& bits, IntegerEncodedVector& result,
+                             u32 nBitsPerValue) {
+    // Implement the algorithm in section C.2.12
+    u32 m[3];
+    u32 q[3];
+    u32 Q;
+
+    // Read the trit encoded block according to
+    // table C.2.15
+    m[0] = bits.ReadBits(nBitsPerValue);
+    Q = bits.ReadBits<3>();
+    m[1] = bits.ReadBits(nBitsPerValue);
+    Q |= bits.ReadBits<2>() << 3;
+    m[2] = bits.ReadBits(nBitsPerValue);
+    Q |= bits.ReadBits<2>() << 5;
+
+    Bits<u32> Qb(Q);
+    if (Qb(1, 2) == 3 && Qb(5, 6) == 0) {
+        q[0] = q[1] = 4;
+        q[2] = (Qb[0] << 2) | ((Qb[4] & ~Qb[0]) << 1) | (Qb[3] & ~Qb[0]);
+    } else {
+        u32 C = 0;
+        if (Qb(1, 2) == 3) {
+            q[2] = 4;
+            C = (Qb(3, 4) << 3) | ((~Qb(5, 6) & 3) << 1) | Qb[0];
+        } else {
+            q[2] = Qb(5, 6);
+            C = Qb(0, 4);
+        }
+
+        Bits<u32> Cb(C);
+        if (Cb(0, 2) == 5) {
+            q[1] = 4;
+            q[0] = Cb(3, 4);
+        } else {
+            q[1] = Cb(3, 4);
+            q[0] = Cb(0, 2);
+        }
+    }
+
+    for (std::size_t i = 0; i < 3; ++i) {
+        IntegerEncodedValue& val = result.emplace_back(IntegerEncoding::Quint, nBitsPerValue);
+        val.bit_value = m[i];
+        val.quint_value = q[i];
+    }
+}
+
+// Fills result with the values that are encoded in the given
+// bitstream. We must know beforehand what the maximum possible
+// value is, and how many values we're decoding.
+static void DecodeIntegerSequence(IntegerEncodedVector& result, InputBitStream& bits, u32 maxRange,
+                                  u32 nValues) {
+    // Determine encoding parameters
+    IntegerEncodedValue val = EncodingsValues[maxRange];
+
+    // Start decoding
+    u32 nValsDecoded = 0;
+    while (nValsDecoded < nValues) {
+        switch (val.encoding) {
+        case IntegerEncoding::Quint:
+            DecodeQuintBlock(bits, result, val.num_bits);
+            nValsDecoded += 3;
+            break;
+
+        case IntegerEncoding::Trit:
+            DecodeTritBlock(bits, result, val.num_bits);
+            nValsDecoded += 5;
+            break;
+
+        case IntegerEncoding::JustBits:
+            val.bit_value = bits.ReadBits(val.num_bits);
+            result.push_back(val);
+            nValsDecoded++;
+            break;
+        }
+    }
+}
+
+struct TexelWeightParams {
+    u32 m_Width = 0;
+    u32 m_Height = 0;
+    bool m_bDualPlane = false;
+    u32 m_MaxWeight = 0;
+    bool m_bError = false;
+    bool m_bVoidExtentLDR = false;
+    bool m_bVoidExtentHDR = false;
+
+    u32 GetPackedBitSize() const {
+        // How many indices do we have?
+        u32 nIdxs = m_Height * m_Width;
+        if (m_bDualPlane) {
+            nIdxs *= 2;
+        }
+
+        return EncodingsValues[m_MaxWeight].GetBitLength(nIdxs);
+    }
+
+    u32 GetNumWeightValues() const {
+        u32 ret = m_Width * m_Height;
+        if (m_bDualPlane) {
+            ret *= 2;
+        }
+        return ret;
+    }
+};
+
+static TexelWeightParams DecodeBlockInfo(InputBitStream& strm) {
+    TexelWeightParams params;
+
+    // Read the entire block mode all at once
+    u16 modeBits = static_cast<u16>(strm.ReadBits<11>());
+
+    // Does this match the void extent block mode?
+    if ((modeBits & 0x01FF) == 0x1FC) {
+        if (modeBits & 0x200) {
+            params.m_bVoidExtentHDR = true;
+        } else {
+            params.m_bVoidExtentLDR = true;
+        }
+
+        // Next two bits must be one.
+        if (!(modeBits & 0x400) || !strm.ReadBit()) {
+            params.m_bError = true;
+        }
+
+        return params;
+    }
+
+    // First check if the last four bits are zero
+    if ((modeBits & 0xF) == 0) {
+        params.m_bError = true;
+        return params;
+    }
+
+    // If the last two bits are zero, then if bits
+    // [6-8] are all ones, this is also reserved.
+    if ((modeBits & 0x3) == 0 && (modeBits & 0x1C0) == 0x1C0) {
+        params.m_bError = true;
+        return params;
+    }
+
+    // Otherwise, there is no error... Figure out the layout
+    // of the block mode. Layout is determined by a number
+    // between 0 and 9 corresponding to table C.2.8 of the
+    // ASTC spec.
+    u32 layout = 0;
+
+    if ((modeBits & 0x1) || (modeBits & 0x2)) {
+        // layout is in [0-4]
+        if (modeBits & 0x8) {
+            // layout is in [2-4]
+            if (modeBits & 0x4) {
+                // layout is in [3-4]
+                if (modeBits & 0x100) {
+                    layout = 4;
+                } else {
+                    layout = 3;
+                }
+            } else {
+                layout = 2;
+            }
+        } else {
+            // layout is in [0-1]
+            if (modeBits & 0x4) {
+                layout = 1;
+            } else {
+                layout = 0;
+            }
+        }
+    } else {
+        // layout is in [5-9]
+        if (modeBits & 0x100) {
+            // layout is in [7-9]
+            if (modeBits & 0x80) {
+                // layout is in [7-8]
+                assert((modeBits & 0x40) == 0U);
+                if (modeBits & 0x20) {
+                    layout = 8;
+                } else {
+                    layout = 7;
+                }
+            } else {
+                layout = 9;
+            }
+        } else {
+            // layout is in [5-6]
+            if (modeBits & 0x80) {
+                layout = 6;
+            } else {
+                layout = 5;
+            }
+        }
+    }
+
+    assert(layout < 10);
+
+    // Determine R
+    u32 R = !!(modeBits & 0x10);
+    if (layout < 5) {
+        R |= (modeBits & 0x3) << 1;
+    } else {
+        R |= (modeBits & 0xC) >> 1;
+    }
+    assert(2 <= R && R <= 7);
+
+    // Determine width & height
+    switch (layout) {
+    case 0: {
+        u32 A = (modeBits >> 5) & 0x3;
+        u32 B = (modeBits >> 7) & 0x3;
+        params.m_Width = B + 4;
+        params.m_Height = A + 2;
+        break;
+    }
+
+    case 1: {
+        u32 A = (modeBits >> 5) & 0x3;
+        u32 B = (modeBits >> 7) & 0x3;
+        params.m_Width = B + 8;
+        params.m_Height = A + 2;
+        break;
+    }
+
+    case 2: {
+        u32 A = (modeBits >> 5) & 0x3;
+        u32 B = (modeBits >> 7) & 0x3;
+        params.m_Width = A + 2;
+        params.m_Height = B + 8;
+        break;
+    }
+
+    case 3: {
+        u32 A = (modeBits >> 5) & 0x3;
+        u32 B = (modeBits >> 7) & 0x1;
+        params.m_Width = A + 2;
+        params.m_Height = B + 6;
+        break;
+    }
+
+    case 4: {
+        u32 A = (modeBits >> 5) & 0x3;
+        u32 B = (modeBits >> 7) & 0x1;
+        params.m_Width = B + 2;
+        params.m_Height = A + 2;
+        break;
+    }
+
+    case 5: {
+        u32 A = (modeBits >> 5) & 0x3;
+        params.m_Width = 12;
+        params.m_Height = A + 2;
+        break;
+    }
+
+    case 6: {
+        u32 A = (modeBits >> 5) & 0x3;
+        params.m_Width = A + 2;
+        params.m_Height = 12;
+        break;
+    }
+
+    case 7: {
+        params.m_Width = 6;
+        params.m_Height = 10;
+        break;
+    }
+
+    case 8: {
+        params.m_Width = 10;
+        params.m_Height = 6;
+        break;
+    }
+
+    case 9: {
+        u32 A = (modeBits >> 5) & 0x3;
+        u32 B = (modeBits >> 9) & 0x3;
+        params.m_Width = A + 6;
+        params.m_Height = B + 6;
+        break;
+    }
+
+    default:
+        assert(false && "Don't know this layout...");
+        params.m_bError = true;
+        break;
+    }
+
+    // Determine whether or not we're using dual planes
+    // and/or high precision layouts.
+    bool D = (layout != 9) && (modeBits & 0x400);
+    bool H = (layout != 9) && (modeBits & 0x200);
+
+    if (H) {
+        const u32 maxWeights[6] = {9, 11, 15, 19, 23, 31};
+        params.m_MaxWeight = maxWeights[R - 2];
+    } else {
+        const u32 maxWeights[6] = {1, 2, 3, 4, 5, 7};
+        params.m_MaxWeight = maxWeights[R - 2];
+    }
+
+    params.m_bDualPlane = D;
+
+    return params;
+}
+
+static void FillVoidExtentLDR(InputBitStream& strm, std::span<u32> outBuf, u32 blockWidth,
+                              u32 blockHeight) {
+    // Don't actually care about the void extent, just read the bits...
+    for (s32 i = 0; i < 4; ++i) {
+        strm.ReadBits<13>();
+    }
+
+    // Decode the RGBA components and renormalize them to the range [0, 255]
+    u16 r = static_cast<u16>(strm.ReadBits<16>());
+    u16 g = static_cast<u16>(strm.ReadBits<16>());
+    u16 b = static_cast<u16>(strm.ReadBits<16>());
+    u16 a = static_cast<u16>(strm.ReadBits<16>());
+
+    u32 rgba = (r >> 8) | (g & 0xFF00) | (static_cast<u32>(b) & 0xFF00) << 8 |
+               (static_cast<u32>(a) & 0xFF00) << 16;
+
+    for (u32 j = 0; j < blockHeight; j++) {
+        for (u32 i = 0; i < blockWidth; i++) {
+            outBuf[j * blockWidth + i] = rgba;
+        }
+    }
+}
+
+static void FillError(std::span<u32> outBuf, u32 blockWidth, u32 blockHeight) {
+    for (u32 j = 0; j < blockHeight; j++) {
+        for (u32 i = 0; i < blockWidth; i++) {
+            outBuf[j * blockWidth + i] = 0xFFFF00FF;
+        }
+    }
+}
+static constexpr u32 ReplicateByteTo16(std::size_t value) {
+    return REPLICATE_BYTE_TO_16_TABLE[value];
+}
+
+static constexpr auto REPLICATE_BIT_TO_7_TABLE = MakeReplicateTable<u32, 1, 7>();
+static constexpr u32 ReplicateBitTo7(std::size_t value) {
+    return REPLICATE_BIT_TO_7_TABLE[value];
+}
+
+static constexpr auto REPLICATE_BIT_TO_9_TABLE = MakeReplicateTable<u32, 1, 9>();
+static constexpr u32 ReplicateBitTo9(std::size_t value) {
+    return REPLICATE_BIT_TO_9_TABLE[value];
+}
+
+static constexpr auto REPLICATE_1_BIT_TO_8_TABLE = MakeReplicateTable<u32, 1, 8>();
+static constexpr auto REPLICATE_2_BIT_TO_8_TABLE = MakeReplicateTable<u32, 2, 8>();
+static constexpr auto REPLICATE_3_BIT_TO_8_TABLE = MakeReplicateTable<u32, 3, 8>();
+static constexpr auto REPLICATE_4_BIT_TO_8_TABLE = MakeReplicateTable<u32, 4, 8>();
+static constexpr auto REPLICATE_5_BIT_TO_8_TABLE = MakeReplicateTable<u32, 5, 8>();
+/// Use a precompiled table with the most common usages, if it's not in the expected range, fallback
+/// to the runtime implementation
+static constexpr u32 FastReplicateTo8(u32 value, u32 num_bits) {
+    switch (num_bits) {
+    case 1:
+        return REPLICATE_1_BIT_TO_8_TABLE[value];
+    case 2:
+        return REPLICATE_2_BIT_TO_8_TABLE[value];
+    case 3:
+        return REPLICATE_3_BIT_TO_8_TABLE[value];
+    case 4:
+        return REPLICATE_4_BIT_TO_8_TABLE[value];
+    case 5:
+        return REPLICATE_5_BIT_TO_8_TABLE[value];
+    case 6:
+        return REPLICATE_6_BIT_TO_8_TABLE[value];
+    case 7:
+        return REPLICATE_7_BIT_TO_8_TABLE[value];
+    case 8:
+        return REPLICATE_8_BIT_TO_8_TABLE[value];
+    default:
+        return Replicate(value, num_bits, 8);
+    }
+}
+
+static constexpr auto REPLICATE_1_BIT_TO_6_TABLE = MakeReplicateTable<u32, 1, 6>();
+static constexpr auto REPLICATE_2_BIT_TO_6_TABLE = MakeReplicateTable<u32, 2, 6>();
+static constexpr auto REPLICATE_3_BIT_TO_6_TABLE = MakeReplicateTable<u32, 3, 6>();
+static constexpr auto REPLICATE_4_BIT_TO_6_TABLE = MakeReplicateTable<u32, 4, 6>();
+static constexpr auto REPLICATE_5_BIT_TO_6_TABLE = MakeReplicateTable<u32, 5, 6>();
+static constexpr u32 FastReplicateTo6(u32 value, u32 num_bits) {
+    switch (num_bits) {
+    case 1:
+        return REPLICATE_1_BIT_TO_6_TABLE[value];
+    case 2:
+        return REPLICATE_2_BIT_TO_6_TABLE[value];
+    case 3:
+        return REPLICATE_3_BIT_TO_6_TABLE[value];
+    case 4:
+        return REPLICATE_4_BIT_TO_6_TABLE[value];
+    case 5:
+        return REPLICATE_5_BIT_TO_6_TABLE[value];
+    default:
+        return Replicate(value, num_bits, 6);
+    }
+}
+
+class Pixel {
+protected:
+    using ChannelType = s16;
+    u8 m_BitDepth[4] = {8, 8, 8, 8};
+    s16 color[4] = {};
+
+public:
+    Pixel() = default;
+    Pixel(u32 a, u32 r, u32 g, u32 b, u32 bitDepth = 8)
+        : m_BitDepth{u8(bitDepth), u8(bitDepth), u8(bitDepth), u8(bitDepth)},
+          color{static_cast<ChannelType>(a), static_cast<ChannelType>(r),
+                static_cast<ChannelType>(g), static_cast<ChannelType>(b)} {}
+
+    // Changes the depth of each pixel. This scales the values to
+    // the appropriate bit depth by either truncating the least
+    // significant bits when going from larger to smaller bit depth
+    // or by repeating the most significant bits when going from
+    // smaller to larger bit depths.
+    void ChangeBitDepth() {
+        for (u32 i = 0; i < 4; i++) {
+            Component(i) = ChangeBitDepth(Component(i), m_BitDepth[i]);
+            m_BitDepth[i] = 8;
+        }
+    }
+
+    template <typename IntType>
+    static float ConvertChannelToFloat(IntType channel, u8 bitDepth) {
+        float denominator = static_cast<float>((1 << bitDepth) - 1);
+        return static_cast<float>(channel) / denominator;
+    }
+
+    // Changes the bit depth of a single component. See the comment
+    // above for how we do this.
+    static ChannelType ChangeBitDepth(Pixel::ChannelType val, u8 oldDepth) {
+        assert(oldDepth <= 8);
+
+        if (oldDepth == 8) {
+            // Do nothing
+            return val;
+        } else if (oldDepth == 0) {
+            return static_cast<ChannelType>((1 << 8) - 1);
+        } else if (8 > oldDepth) {
+            return static_cast<ChannelType>(FastReplicateTo8(static_cast<u32>(val), oldDepth));
+        } else {
+            // oldDepth > newDepth
+            const u8 bitsWasted = static_cast<u8>(oldDepth - 8);
+            u16 v = static_cast<u16>(val);
+            v = static_cast<u16>((v + (1 << (bitsWasted - 1))) >> bitsWasted);
+            v = ::std::min<u16>(::std::max<u16>(0, v), static_cast<u16>((1 << 8) - 1));
+            return static_cast<u8>(v);
+        }
+
+        assert(false && "We shouldn't get here.");
+        return 0;
+    }
+
+    const ChannelType& A() const {
+        return color[0];
+    }
+    ChannelType& A() {
+        return color[0];
+    }
+    const ChannelType& R() const {
+        return color[1];
+    }
+    ChannelType& R() {
+        return color[1];
+    }
+    const ChannelType& G() const {
+        return color[2];
+    }
+    ChannelType& G() {
+        return color[2];
+    }
+    const ChannelType& B() const {
+        return color[3];
+    }
+    ChannelType& B() {
+        return color[3];
+    }
+    const ChannelType& Component(u32 idx) const {
+        return color[idx];
+    }
+    ChannelType& Component(u32 idx) {
+        return color[idx];
+    }
+
+    void GetBitDepth(u8 (&outDepth)[4]) const {
+        for (s32 i = 0; i < 4; i++) {
+            outDepth[i] = m_BitDepth[i];
+        }
+    }
+
+    // Take all of the components, transform them to their 8-bit variants,
+    // and then pack each channel into an R8G8B8A8 32-bit integer. We assume
+    // that the architecture is little-endian, so the alpha channel will end
+    // up in the most-significant byte.
+    u32 Pack() const {
+        Pixel eightBit(*this);
+        eightBit.ChangeBitDepth();
+
+        u32 r = 0;
+        r |= eightBit.A();
+        r <<= 8;
+        r |= eightBit.B();
+        r <<= 8;
+        r |= eightBit.G();
+        r <<= 8;
+        r |= eightBit.R();
+        return r;
+    }
+
+    // Clamps the pixel to the range [0,255]
+    void ClampByte() {
+        for (u32 i = 0; i < 4; i++) {
+            color[i] = (color[i] < 0) ? 0 : ((color[i] > 255) ? 255 : color[i]);
+        }
+    }
+
+    void MakeOpaque() {
+        A() = 255;
+    }
+};
+
+static void DecodeColorValues(u32* out, std::span<u8> data, const u32* modes, const u32 nPartitions,
+                              const u32 nBitsForColorData) {
+    // First figure out how many color values we have
+    u32 nValues = 0;
+    for (u32 i = 0; i < nPartitions; i++) {
+        nValues += ((modes[i] >> 2) + 1) << 1;
+    }
+
+    // Then based on the number of values and the remaining number of bits,
+    // figure out the max value for each of them...
+    u32 range = 256;
+    while (--range > 0) {
+        IntegerEncodedValue val = EncodingsValues[range];
+        u32 bitLength = val.GetBitLength(nValues);
+        if (bitLength <= nBitsForColorData) {
+            // Find the smallest possible range that matches the given encoding
+            while (--range > 0) {
+                IntegerEncodedValue newval = EncodingsValues[range];
+                if (!newval.MatchesEncoding(val)) {
+                    break;
+                }
+            }
+
+            // Return to last matching range.
+            range++;
+            break;
+        }
+    }
+
+    // We now have enough to decode our integer sequence.
+    IntegerEncodedVector decodedColorValues;
+
+    InputBitStream colorStream(data, 0);
+    DecodeIntegerSequence(decodedColorValues, colorStream, range, nValues);
+
+    // Once we have the decoded values, we need to dequantize them to the 0-255 range
+    // This procedure is outlined in ASTC spec C.2.13
+    u32 outIdx = 0;
+    for (auto itr = decodedColorValues.begin(); itr != decodedColorValues.end(); ++itr) {
+        // Have we already decoded all that we need?
+        if (outIdx >= nValues) {
+            break;
+        }
+
+        const IntegerEncodedValue& val = *itr;
+        u32 bitlen = val.num_bits;
+        u32 bitval = val.bit_value;
+
+        assert(bitlen >= 1);
+
+        u32 A = 0, B = 0, C = 0, D = 0;
+        // A is just the lsb replicated 9 times.
+        A = ReplicateBitTo9(bitval & 1);
+
+        switch (val.encoding) {
+        // Replicate bits
+        case IntegerEncoding::JustBits:
+            out[outIdx++] = FastReplicateTo8(bitval, bitlen);
+            break;
+
+        // Use algorithm in C.2.13
+        case IntegerEncoding::Trit: {
+
+            D = val.trit_value;
+
+            switch (bitlen) {
+            case 1: {
+                C = 204;
+            } break;
+
+            case 2: {
+                C = 93;
+                // B = b000b0bb0
+                u32 b = (bitval >> 1) & 1;
+                B = (b << 8) | (b << 4) | (b << 2) | (b << 1);
+            } break;
+
+            case 3: {
+                C = 44;
+                // B = cb000cbcb
+                u32 cb = (bitval >> 1) & 3;
+                B = (cb << 7) | (cb << 2) | cb;
+            } break;
+
+            case 4: {
+                C = 22;
+                // B = dcb000dcb
+                u32 dcb = (bitval >> 1) & 7;
+                B = (dcb << 6) | dcb;
+            } break;
+
+            case 5: {
+                C = 11;
+                // B = edcb000ed
+                u32 edcb = (bitval >> 1) & 0xF;
+                B = (edcb << 5) | (edcb >> 2);
+            } break;
+
+            case 6: {
+                C = 5;
+                // B = fedcb000f
+                u32 fedcb = (bitval >> 1) & 0x1F;
+                B = (fedcb << 4) | (fedcb >> 4);
+            } break;
+
+            default:
+                assert(false && "Unsupported trit encoding for color values!");
+                break;
+            } // switch(bitlen)
+        }     // case IntegerEncoding::Trit
+        break;
+
+        case IntegerEncoding::Quint: {
+
+            D = val.quint_value;
+
+            switch (bitlen) {
+            case 1: {
+                C = 113;
+            } break;
+
+            case 2: {
+                C = 54;
+                // B = b0000bb00
+                u32 b = (bitval >> 1) & 1;
+                B = (b << 8) | (b << 3) | (b << 2);
+            } break;
+
+            case 3: {
+                C = 26;
+                // B = cb0000cbc
+                u32 cb = (bitval >> 1) & 3;
+                B = (cb << 7) | (cb << 1) | (cb >> 1);
+            } break;
+
+            case 4: {
+                C = 13;
+                // B = dcb0000dc
+                u32 dcb = (bitval >> 1) & 7;
+                B = (dcb << 6) | (dcb >> 1);
+            } break;
+
+            case 5: {
+                C = 6;
+                // B = edcb0000e
+                u32 edcb = (bitval >> 1) & 0xF;
+                B = (edcb << 5) | (edcb >> 3);
+            } break;
+
+            default:
+                assert(false && "Unsupported quint encoding for color values!");
+                break;
+            } // switch(bitlen)
+        }     // case IntegerEncoding::Quint
+        break;
+        } // switch(val.encoding)
+
+        if (val.encoding != IntegerEncoding::JustBits) {
+            u32 T = D * C + B;
+            T ^= A;
+            T = (A & 0x80) | (T >> 2);
+            out[outIdx++] = T;
+        }
+    }
+
+    // Make sure that each of our values is in the proper range...
+    for (u32 i = 0; i < nValues; i++) {
+        assert(out[i] <= 255);
+    }
+}
+
+static u32 UnquantizeTexelWeight(const IntegerEncodedValue& val) {
+    u32 bitval = val.bit_value;
+    u32 bitlen = val.num_bits;
+
+    u32 A = ReplicateBitTo7(bitval & 1);
+    u32 B = 0, C = 0, D = 0;
+
+    u32 result = 0;
+    switch (val.encoding) {
+    case IntegerEncoding::JustBits:
+        result = FastReplicateTo6(bitval, bitlen);
+        break;
+
+    case IntegerEncoding::Trit: {
+        D = val.trit_value;
+        assert(D < 3);
+
+        switch (bitlen) {
+        case 0: {
+            u32 results[3] = {0, 32, 63};
+            result = results[D];
+        } break;
+
+        case 1: {
+            C = 50;
+        } break;
+
+        case 2: {
+            C = 23;
+            u32 b = (bitval >> 1) & 1;
+            B = (b << 6) | (b << 2) | b;
+        } break;
+
+        case 3: {
+            C = 11;
+            u32 cb = (bitval >> 1) & 3;
+            B = (cb << 5) | cb;
+        } break;
+
+        default:
+            assert(false && "Invalid trit encoding for texel weight");
+            break;
+        }
+    } break;
+
+    case IntegerEncoding::Quint: {
+        D = val.quint_value;
+        assert(D < 5);
+
+        switch (bitlen) {
+        case 0: {
+            u32 results[5] = {0, 16, 32, 47, 63};
+            result = results[D];
+        } break;
+
+        case 1: {
+            C = 28;
+        } break;
+
+        case 2: {
+            C = 13;
+            u32 b = (bitval >> 1) & 1;
+            B = (b << 6) | (b << 1);
+        } break;
+
+        default:
+            assert(false && "Invalid quint encoding for texel weight");
+            break;
+        }
+    } break;
+    }
+
+    if (val.encoding != IntegerEncoding::JustBits && bitlen > 0) {
+        // Decode the value...
+        result = D * C + B;
+        result ^= A;
+        result = (A & 0x20) | (result >> 2);
+    }
+
+    assert(result < 64);
+
+    // Change from [0,63] to [0,64]
+    if (result > 32) {
+        result += 1;
+    }
+
+    return result;
+}
+
+static void UnquantizeTexelWeights(u32 out[2][144], const IntegerEncodedVector& weights,
+                                   const TexelWeightParams& params, const u32 blockWidth,
+                                   const u32 blockHeight) {
+    u32 weightIdx = 0;
+    u32 unquantized[2][144];
+
+    for (auto itr = weights.begin(); itr != weights.end(); ++itr) {
+        unquantized[0][weightIdx] = UnquantizeTexelWeight(*itr);
+
+        if (params.m_bDualPlane) {
+            ++itr;
+            unquantized[1][weightIdx] = UnquantizeTexelWeight(*itr);
+            if (itr == weights.end()) {
+                break;
+            }
+        }
+
+        if (++weightIdx >= (params.m_Width * params.m_Height))
+            break;
+    }
+
+    // Do infill if necessary (Section C.2.18) ...
+    u32 Ds = (1024 + (blockWidth / 2)) / (blockWidth - 1);
+    u32 Dt = (1024 + (blockHeight / 2)) / (blockHeight - 1);
+
+    const u32 kPlaneScale = params.m_bDualPlane ? 2U : 1U;
+    for (u32 plane = 0; plane < kPlaneScale; plane++)
+        for (u32 t = 0; t < blockHeight; t++)
+            for (u32 s = 0; s < blockWidth; s++) {
+                u32 cs = Ds * s;
+                u32 ct = Dt * t;
+
+                u32 gs = (cs * (params.m_Width - 1) + 32) >> 6;
+                u32 gt = (ct * (params.m_Height - 1) + 32) >> 6;
+
+                u32 js = gs >> 4;
+                u32 fs = gs & 0xF;
+
+                u32 jt = gt >> 4;
+                u32 ft = gt & 0x0F;
+
+                u32 w11 = (fs * ft + 8) >> 4;
+                u32 w10 = ft - w11;
+                u32 w01 = fs - w11;
+                u32 w00 = 16 - fs - ft + w11;
+
+                u32 v0 = js + jt * params.m_Width;
+
+#define FIND_TEXEL(tidx, bidx)                                                                     \
+    u32 p##bidx = 0;                                                                               \
+    do {                                                                                           \
+        if ((tidx) < (params.m_Width * params.m_Height)) {                                         \
+            p##bidx = unquantized[plane][(tidx)];                                                  \
+        }                                                                                          \
+    } while (0)
+
+                FIND_TEXEL(v0, 00);
+                FIND_TEXEL(v0 + 1, 01);
+                FIND_TEXEL(v0 + params.m_Width, 10);
+                FIND_TEXEL(v0 + params.m_Width + 1, 11);
+
+#undef FIND_TEXEL
+
+                out[plane][t * blockWidth + s] =
+                    (p00 * w00 + p01 * w01 + p10 * w10 + p11 * w11 + 8) >> 4;
+            }
+}
+
+// Transfers a bit as described in C.2.14
+static inline void BitTransferSigned(int& a, int& b) {
+    b >>= 1;
+    b |= a & 0x80;
+    a >>= 1;
+    a &= 0x3F;
+    if (a & 0x20)
+        a -= 0x40;
+}
+
+// Adds more precision to the blue channel as described
+// in C.2.14
+static inline Pixel BlueContract(s32 a, s32 r, s32 g, s32 b) {
+    return Pixel(static_cast<s16>(a), static_cast<s16>((r + b) >> 1),
+                 static_cast<s16>((g + b) >> 1), static_cast<s16>(b));
+}
+
+// Partition selection functions as specified in
+// C.2.21
+static inline u32 hash52(u32 p) {
+    p ^= p >> 15;
+    p -= p << 17;
+    p += p << 7;
+    p += p << 4;
+    p ^= p >> 5;
+    p += p << 16;
+    p ^= p >> 7;
+    p ^= p >> 3;
+    p ^= p << 6;
+    p ^= p >> 17;
+    return p;
+}
+
+static u32 SelectPartition(s32 seed, s32 x, s32 y, s32 z, s32 partitionCount, s32 smallBlock) {
+    if (1 == partitionCount)
+        return 0;
+
+    if (smallBlock) {
+        x <<= 1;
+        y <<= 1;
+        z <<= 1;
+    }
+
+    seed += (partitionCount - 1) * 1024;
+
+    u32 rnum = hash52(static_cast<u32>(seed));
+    u8 seed1 = static_cast<u8>(rnum & 0xF);
+    u8 seed2 = static_cast<u8>((rnum >> 4) & 0xF);
+    u8 seed3 = static_cast<u8>((rnum >> 8) & 0xF);
+    u8 seed4 = static_cast<u8>((rnum >> 12) & 0xF);
+    u8 seed5 = static_cast<u8>((rnum >> 16) & 0xF);
+    u8 seed6 = static_cast<u8>((rnum >> 20) & 0xF);
+    u8 seed7 = static_cast<u8>((rnum >> 24) & 0xF);
+    u8 seed8 = static_cast<u8>((rnum >> 28) & 0xF);
+    u8 seed9 = static_cast<u8>((rnum >> 18) & 0xF);
+    u8 seed10 = static_cast<u8>((rnum >> 22) & 0xF);
+    u8 seed11 = static_cast<u8>((rnum >> 26) & 0xF);
+    u8 seed12 = static_cast<u8>(((rnum >> 30) | (rnum << 2)) & 0xF);
+
+    seed1 = static_cast<u8>(seed1 * seed1);
+    seed2 = static_cast<u8>(seed2 * seed2);
+    seed3 = static_cast<u8>(seed3 * seed3);
+    seed4 = static_cast<u8>(seed4 * seed4);
+    seed5 = static_cast<u8>(seed5 * seed5);
+    seed6 = static_cast<u8>(seed6 * seed6);
+    seed7 = static_cast<u8>(seed7 * seed7);
+    seed8 = static_cast<u8>(seed8 * seed8);
+    seed9 = static_cast<u8>(seed9 * seed9);
+    seed10 = static_cast<u8>(seed10 * seed10);
+    seed11 = static_cast<u8>(seed11 * seed11);
+    seed12 = static_cast<u8>(seed12 * seed12);
+
+    s32 sh1, sh2, sh3;
+    if (seed & 1) {
+        sh1 = (seed & 2) ? 4 : 5;
+        sh2 = (partitionCount == 3) ? 6 : 5;
+    } else {
+        sh1 = (partitionCount == 3) ? 6 : 5;
+        sh2 = (seed & 2) ? 4 : 5;
+    }
+    sh3 = (seed & 0x10) ? sh1 : sh2;
+
+    seed1 = static_cast<u8>(seed1 >> sh1);
+    seed2 = static_cast<u8>(seed2 >> sh2);
+    seed3 = static_cast<u8>(seed3 >> sh1);
+    seed4 = static_cast<u8>(seed4 >> sh2);
+    seed5 = static_cast<u8>(seed5 >> sh1);
+    seed6 = static_cast<u8>(seed6 >> sh2);
+    seed7 = static_cast<u8>(seed7 >> sh1);
+    seed8 = static_cast<u8>(seed8 >> sh2);
+    seed9 = static_cast<u8>(seed9 >> sh3);
+    seed10 = static_cast<u8>(seed10 >> sh3);
+    seed11 = static_cast<u8>(seed11 >> sh3);
+    seed12 = static_cast<u8>(seed12 >> sh3);
+
+    s32 a = seed1 * x + seed2 * y + seed11 * z + (rnum >> 14);
+    s32 b = seed3 * x + seed4 * y + seed12 * z + (rnum >> 10);
+    s32 c = seed5 * x + seed6 * y + seed9 * z + (rnum >> 6);
+    s32 d = seed7 * x + seed8 * y + seed10 * z + (rnum >> 2);
+
+    a &= 0x3F;
+    b &= 0x3F;
+    c &= 0x3F;
+    d &= 0x3F;
+
+    if (partitionCount < 4)
+        d = 0;
+    if (partitionCount < 3)
+        c = 0;
+
+    if (a >= b && a >= c && a >= d)
+        return 0;
+    else if (b >= c && b >= d)
+        return 1;
+    else if (c >= d)
+        return 2;
+    return 3;
+}
+
+static inline u32 Select2DPartition(s32 seed, s32 x, s32 y, s32 partitionCount, s32 smallBlock) {
+    return SelectPartition(seed, x, y, 0, partitionCount, smallBlock);
+}
+
+// Section C.2.14
+static void ComputeEndpoints(Pixel& ep1, Pixel& ep2, const u32*& colorValues,
+                             u32 colorEndpointMode) {
+#define READ_UINT_VALUES(N)                                                                        \
+    u32 v[N];                                                                                      \
+    for (u32 i = 0; i < N; i++) {                                                                  \
+        v[i] = *(colorValues++);                                                                   \
+    }
+
+#define READ_INT_VALUES(N)                                                                         \
+    s32 v[N];                                                                                      \
+    for (u32 i = 0; i < N; i++) {                                                                  \
+        v[i] = static_cast<int>(*(colorValues++));                                                 \
+    }
+
+    switch (colorEndpointMode) {
+    case 0: {
+        READ_UINT_VALUES(2)
+        ep1 = Pixel(0xFF, v[0], v[0], v[0]);
+        ep2 = Pixel(0xFF, v[1], v[1], v[1]);
+    } break;
+
+    case 1: {
+        READ_UINT_VALUES(2)
+        u32 L0 = (v[0] >> 2) | (v[1] & 0xC0);
+        u32 L1 = std::max(L0 + (v[1] & 0x3F), 0xFFU);
+        ep1 = Pixel(0xFF, L0, L0, L0);
+        ep2 = Pixel(0xFF, L1, L1, L1);
+    } break;
+
+    case 4: {
+        READ_UINT_VALUES(4)
+        ep1 = Pixel(v[2], v[0], v[0], v[0]);
+        ep2 = Pixel(v[3], v[1], v[1], v[1]);
+    } break;
+
+    case 5: {
+        READ_INT_VALUES(4)
+        BitTransferSigned(v[1], v[0]);
+        BitTransferSigned(v[3], v[2]);
+        ep1 = Pixel(v[2], v[0], v[0], v[0]);
+        ep2 = Pixel(v[2] + v[3], v[0] + v[1], v[0] + v[1], v[0] + v[1]);
+        ep1.ClampByte();
+        ep2.ClampByte();
+    } break;
+
+    case 6: {
+        READ_UINT_VALUES(4)
+        ep1 = Pixel(0xFF, v[0] * v[3] >> 8, v[1] * v[3] >> 8, v[2] * v[3] >> 8);
+        ep2 = Pixel(0xFF, v[0], v[1], v[2]);
+    } break;
+
+    case 8: {
+        READ_UINT_VALUES(6)
+        if (v[1] + v[3] + v[5] >= v[0] + v[2] + v[4]) {
+            ep1 = Pixel(0xFF, v[0], v[2], v[4]);
+            ep2 = Pixel(0xFF, v[1], v[3], v[5]);
+        } else {
+            ep1 = BlueContract(0xFF, v[1], v[3], v[5]);
+            ep2 = BlueContract(0xFF, v[0], v[2], v[4]);
+        }
+    } break;
+
+    case 9: {
+        READ_INT_VALUES(6)
+        BitTransferSigned(v[1], v[0]);
+        BitTransferSigned(v[3], v[2]);
+        BitTransferSigned(v[5], v[4]);
+        if (v[1] + v[3] + v[5] >= 0) {
+            ep1 = Pixel(0xFF, v[0], v[2], v[4]);
+            ep2 = Pixel(0xFF, v[0] + v[1], v[2] + v[3], v[4] + v[5]);
+        } else {
+            ep1 = BlueContract(0xFF, v[0] + v[1], v[2] + v[3], v[4] + v[5]);
+            ep2 = BlueContract(0xFF, v[0], v[2], v[4]);
+        }
+        ep1.ClampByte();
+        ep2.ClampByte();
+    } break;
+
+    case 10: {
+        READ_UINT_VALUES(6)
+        ep1 = Pixel(v[4], v[0] * v[3] >> 8, v[1] * v[3] >> 8, v[2] * v[3] >> 8);
+        ep2 = Pixel(v[5], v[0], v[1], v[2]);
+    } break;
+
+    case 12: {
+        READ_UINT_VALUES(8)
+        if (v[1] + v[3] + v[5] >= v[0] + v[2] + v[4]) {
+            ep1 = Pixel(v[6], v[0], v[2], v[4]);
+            ep2 = Pixel(v[7], v[1], v[3], v[5]);
+        } else {
+            ep1 = BlueContract(v[7], v[1], v[3], v[5]);
+            ep2 = BlueContract(v[6], v[0], v[2], v[4]);
+        }
+    } break;
+
+    case 13: {
+        READ_INT_VALUES(8)
+        BitTransferSigned(v[1], v[0]);
+        BitTransferSigned(v[3], v[2]);
+        BitTransferSigned(v[5], v[4]);
+        BitTransferSigned(v[7], v[6]);
+        if (v[1] + v[3] + v[5] >= 0) {
+            ep1 = Pixel(v[6], v[0], v[2], v[4]);
+            ep2 = Pixel(v[7] + v[6], v[0] + v[1], v[2] + v[3], v[4] + v[5]);
+        } else {
+            ep1 = BlueContract(v[6] + v[7], v[0] + v[1], v[2] + v[3], v[4] + v[5]);
+            ep2 = BlueContract(v[6], v[0], v[2], v[4]);
+        }
+        ep1.ClampByte();
+        ep2.ClampByte();
+    } break;
+
+    default:
+        assert(false && "Unsupported color endpoint mode (is it HDR?)");
+        break;
+    }
+
+#undef READ_UINT_VALUES
+#undef READ_INT_VALUES
+}
+
+static void DecompressBlock(std::span<const u8, 16> inBuf, const u32 blockWidth,
+                            const u32 blockHeight, std::span<u32, 12 * 12> outBuf) {
+    InputBitStream strm(inBuf);
+    TexelWeightParams weightParams = DecodeBlockInfo(strm);
+
+    // Was there an error?
+    if (weightParams.m_bError) {
+        assert(false && "Invalid block mode");
+        FillError(outBuf, blockWidth, blockHeight);
+        return;
+    }
+
+    if (weightParams.m_bVoidExtentLDR) {
+        FillVoidExtentLDR(strm, outBuf, blockWidth, blockHeight);
+        return;
+    }
+
+    if (weightParams.m_bVoidExtentHDR) {
+        assert(false && "HDR void extent blocks are unsupported!");
+        FillError(outBuf, blockWidth, blockHeight);
+        return;
+    }
+
+    if (weightParams.m_Width > blockWidth) {
+        assert(false && "Texel weight grid width should be smaller than block width");
+        FillError(outBuf, blockWidth, blockHeight);
+        return;
+    }
+
+    if (weightParams.m_Height > blockHeight) {
+        assert(false && "Texel weight grid height should be smaller than block height");
+        FillError(outBuf, blockWidth, blockHeight);
+        return;
+    }
+
+    // Read num partitions
+    u32 nPartitions = strm.ReadBits<2>() + 1;
+    assert(nPartitions <= 4);
+
+    if (nPartitions == 4 && weightParams.m_bDualPlane) {
+        assert(false && "Dual plane mode is incompatible with four partition blocks");
+        FillError(outBuf, blockWidth, blockHeight);
+        return;
+    }
+
+    // Based on the number of partitions, read the color endpoint mode for
+    // each partition.
+
+    // Determine partitions, partition index, and color endpoint modes
+    s32 planeIdx = -1;
+    u32 partitionIndex;
+    u32 colorEndpointMode[4] = {0, 0, 0, 0};
+
+    // Define color data.
+    u8 colorEndpointData[16];
+    memset(colorEndpointData, 0, sizeof(colorEndpointData));
+    OutputBitStream colorEndpointStream(colorEndpointData, 16 * 8, 0);
+
+    // Read extra config data...
+    u32 baseCEM = 0;
+    if (nPartitions == 1) {
+        colorEndpointMode[0] = strm.ReadBits<4>();
+        partitionIndex = 0;
+    } else {
+        partitionIndex = strm.ReadBits<10>();
+        baseCEM = strm.ReadBits<6>();
+    }
+    u32 baseMode = (baseCEM & 3);
+
+    // Remaining bits are color endpoint data...
+    u32 nWeightBits = weightParams.GetPackedBitSize();
+    s32 remainingBits = 128 - nWeightBits - static_cast<int>(strm.GetBitsRead());
+
+    // Consider extra bits prior to texel data...
+    u32 extraCEMbits = 0;
+    if (baseMode) {
+        switch (nPartitions) {
+        case 2:
+            extraCEMbits += 2;
+            break;
+        case 3:
+            extraCEMbits += 5;
+            break;
+        case 4:
+            extraCEMbits += 8;
+            break;
+        default:
+            assert(false);
+            break;
+        }
+    }
+    remainingBits -= extraCEMbits;
+
+    // Do we have a dual plane situation?
+    u32 planeSelectorBits = 0;
+    if (weightParams.m_bDualPlane) {
+        planeSelectorBits = 2;
+    }
+    remainingBits -= planeSelectorBits;
+
+    // Read color data...
+    u32 colorDataBits = remainingBits;
+    while (remainingBits > 0) {
+        u32 nb = std::min(remainingBits, 8);
+        u32 b = strm.ReadBits(nb);
+        colorEndpointStream.WriteBits(b, nb);
+        remainingBits -= 8;
+    }
+
+    // Read the plane selection bits
+    planeIdx = strm.ReadBits(planeSelectorBits);
+
+    // Read the rest of the CEM
+    if (baseMode) {
+        u32 extraCEM = strm.ReadBits(extraCEMbits);
+        u32 CEM = (extraCEM << 6) | baseCEM;
+        CEM >>= 2;
+
+        bool C[4] = {0};
+        for (u32 i = 0; i < nPartitions; i++) {
+            C[i] = CEM & 1;
+            CEM >>= 1;
+        }
+
+        u8 M[4] = {0};
+        for (u32 i = 0; i < nPartitions; i++) {
+            M[i] = CEM & 3;
+            CEM >>= 2;
+            assert(M[i] <= 3);
+        }
+
+        for (u32 i = 0; i < nPartitions; i++) {
+            colorEndpointMode[i] = baseMode;
+            if (!(C[i]))
+                colorEndpointMode[i] -= 1;
+            colorEndpointMode[i] <<= 2;
+            colorEndpointMode[i] |= M[i];
+        }
+    } else if (nPartitions > 1) {
+        u32 CEM = baseCEM >> 2;
+        for (u32 i = 0; i < nPartitions; i++) {
+            colorEndpointMode[i] = CEM;
+        }
+    }
+
+    // Make sure everything up till here is sane.
+    for (u32 i = 0; i < nPartitions; i++) {
+        assert(colorEndpointMode[i] < 16);
+    }
+    assert(strm.GetBitsRead() + weightParams.GetPackedBitSize() == 128);
+
+    // Decode both color data and texel weight data
+    u32 colorValues[32]; // Four values, two endpoints, four maximum paritions
+    DecodeColorValues(colorValues, colorEndpointData, colorEndpointMode, nPartitions,
+                      colorDataBits);
+
+    Pixel endpoints[4][2];
+    const u32* colorValuesPtr = colorValues;
+    for (u32 i = 0; i < nPartitions; i++) {
+        ComputeEndpoints(endpoints[i][0], endpoints[i][1], colorValuesPtr, colorEndpointMode[i]);
+    }
+
+    // Read the texel weight data..
+    std::array<u8, 16> texelWeightData;
+    std::ranges::copy(inBuf, texelWeightData.begin());
+
+    // Reverse everything
+    for (u32 i = 0; i < 8; i++) {
+// Taken from http://graphics.stanford.edu/~seander/bithacks.html#ReverseByteWith64Bits
+#define REVERSE_BYTE(b) (((b)*0x80200802ULL) & 0x0884422110ULL) * 0x0101010101ULL >> 32
+        u8 a = static_cast<u8>(REVERSE_BYTE(texelWeightData[i]));
+        u8 b = static_cast<u8>(REVERSE_BYTE(texelWeightData[15 - i]));
+#undef REVERSE_BYTE
+
+        texelWeightData[i] = b;
+        texelWeightData[15 - i] = a;
+    }
+
+    // Make sure that higher non-texel bits are set to zero
+    const u32 clearByteStart = (weightParams.GetPackedBitSize() >> 3) + 1;
+    if (clearByteStart > 0 && clearByteStart <= texelWeightData.size()) {
+        texelWeightData[clearByteStart - 1] &=
+            static_cast<u8>((1 << (weightParams.GetPackedBitSize() % 8)) - 1);
+        std::memset(texelWeightData.data() + clearByteStart, 0,
+                    std::min(16U - clearByteStart, 16U));
+    }
+
+    IntegerEncodedVector texelWeightValues;
+
+    InputBitStream weightStream(texelWeightData);
+
+    DecodeIntegerSequence(texelWeightValues, weightStream, weightParams.m_MaxWeight,
+                          weightParams.GetNumWeightValues());
+
+    // Blocks can be at most 12x12, so we can have as many as 144 weights
+    u32 weights[2][144];
+    UnquantizeTexelWeights(weights, texelWeightValues, weightParams, blockWidth, blockHeight);
+
+    // Now that we have endpoints and weights, we can interpolate and generate
+    // the proper decoding...
+    for (u32 j = 0; j < blockHeight; j++)
+        for (u32 i = 0; i < blockWidth; i++) {
+            u32 partition = Select2DPartition(partitionIndex, i, j, nPartitions,
+                                              (blockHeight * blockWidth) < 32);
+            assert(partition < nPartitions);
+
+            Pixel p;
+            for (u32 c = 0; c < 4; c++) {
+                u32 C0 = endpoints[partition][0].Component(c);
+                C0 = ReplicateByteTo16(C0);
+                u32 C1 = endpoints[partition][1].Component(c);
+                C1 = ReplicateByteTo16(C1);
+
+                u32 plane = 0;
+                if (weightParams.m_bDualPlane && (((planeIdx + 1) & 3) == c)) {
+                    plane = 1;
+                }
+
+                u32 weight = weights[plane][j * blockWidth + i];
+                u32 C = (C0 * (64 - weight) + C1 * weight + 32) / 64;
+                if (C == 65535) {
+                    p.Component(c) = 255;
+                } else {
+                    double Cf = static_cast<double>(C);
+                    p.Component(c) = static_cast<u16>(255.0 * (Cf / 65536.0) + 0.5);
+                }
+            }
+
+            outBuf[j * blockWidth + i] = p.Pack();
+        }
+}
+
+void Decompress(std::span<const uint8_t> data, uint32_t width, uint32_t height, uint32_t depth,
+                uint32_t block_width, uint32_t block_height, std::span<uint8_t> output) {
+    u32 block_index = 0;
+    std::size_t depth_offset = 0;
+    for (u32 z = 0; z < depth; z++) {
+        for (u32 y = 0; y < height; y += block_height) {
+            for (u32 x = 0; x < width; x += block_width) {
+                const std::span<const u8, 16> blockPtr{data.subspan(block_index * 16, 16)};
+
+                // Blocks can be at most 12x12
+                std::array<u32, 12 * 12> uncompData;
+                DecompressBlock(blockPtr, block_width, block_height, uncompData);
+
+                u32 decompWidth = std::min(block_width, width - x);
+                u32 decompHeight = std::min(block_height, height - y);
+
+                const std::span<u8> outRow = output.subspan(depth_offset + (y * width + x) * 4);
+                for (u32 jj = 0; jj < decompHeight; jj++) {
+                    std::memcpy(outRow.data() + jj * width * 4,
+                                uncompData.data() + jj * block_width, decompWidth * 4);
+                }
+                ++block_index;
+            }
+        }
+        depth_offset += height * width * 4;
+    }
+}
+
+} // namespace Tegra::Texture::ASTC
diff --git a/src/video_core/textures/astc.h b/src/video_core/textures/astc.h
index c1c73fda5..c1c37dfe7 100644
--- a/src/video_core/textures/astc.h
+++ b/src/video_core/textures/astc.h
@@ -129,4 +129,7 @@ struct AstcBufferData {
     decltype(REPLICATE_BYTE_TO_16_TABLE) replicate_byte_to_16 = REPLICATE_BYTE_TO_16_TABLE;
 } constexpr ASTC_BUFFER_DATA;
 
+void Decompress(std::span<const uint8_t> data, uint32_t width, uint32_t height, uint32_t depth,
+                uint32_t block_width, uint32_t block_height, std::span<uint8_t> output);
+
 } // namespace Tegra::Texture::ASTC