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