DirectDraw Surface image decoder

Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>

1 files changed, 660 insertions, 0 deletions

diff --git a/libavcodec/dds.c b/libavcodec/dds.c
new file mode 100644
index 0000000000..9652f273fc
--- /dev/null
+++ b/libavcodec/dds.c
@@ -0,0 +1,660 @@
+/*
+ * DirectDraw Surface image decoder
+ * Copyright (C) 2015 Vittorio Giovara <vittorio.giovara@gmail.com>
+ *
+ * This file is part of Libav.
+ *
+ * Libav is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * Libav is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * DDS decoder
+ *
+ * https://msdn.microsoft.com/en-us/library/bb943982%28v=vs.85%29.aspx
+ */
+
+#include <stdint.h>
+
+#include "libavutil/imgutils.h"
+
+#include "avcodec.h"
+#include "bytestream.h"
+#include "internal.h"
+#include "texturedsp.h"
+#include "thread.h"
+
+#define DDPF_FOURCC    (1 <<  2)
+#define DDPF_PALETTE   (1 <<  5)
+#define DDPF_NORMALMAP (1 << 31)
+
+enum DDSPostProc {
+    DDS_NONE = 0,
+    DDS_ALPHA_EXP,
+    DDS_NORMAL_MAP,
+    DDS_RAW_YCOCG,
+    DDS_SWAP_ALPHA,
+    DDS_SWIZZLE_A2XY,
+    DDS_SWIZZLE_RBXG,
+    DDS_SWIZZLE_RGXB,
+    DDS_SWIZZLE_RXBG,
+    DDS_SWIZZLE_RXGB,
+    DDS_SWIZZLE_XGBR,
+    DDS_SWIZZLE_XRBG,
+    DDS_SWIZZLE_XGXR,
+} DDSPostProc;
+
+enum DDSDXGIFormat {
+    DXGI_FORMAT_R16G16B16A16_TYPELESS       =  9,
+    DXGI_FORMAT_R16G16B16A16_FLOAT          = 10,
+    DXGI_FORMAT_R16G16B16A16_UNORM          = 11,
+    DXGI_FORMAT_R16G16B16A16_UINT           = 12,
+    DXGI_FORMAT_R16G16B16A16_SNORM          = 13,
+    DXGI_FORMAT_R16G16B16A16_SINT           = 14,
+
+    DXGI_FORMAT_R8G8B8A8_TYPELESS           = 27,
+    DXGI_FORMAT_R8G8B8A8_UNORM              = 28,
+    DXGI_FORMAT_R8G8B8A8_UNORM_SRGB         = 29,
+    DXGI_FORMAT_R8G8B8A8_UINT               = 30,
+    DXGI_FORMAT_R8G8B8A8_SNORM              = 31,
+    DXGI_FORMAT_R8G8B8A8_SINT               = 32,
+
+    DXGI_FORMAT_BC1_TYPELESS                = 70,
+    DXGI_FORMAT_BC1_UNORM                   = 71,
+    DXGI_FORMAT_BC1_UNORM_SRGB              = 72,
+    DXGI_FORMAT_BC2_TYPELESS                = 73,
+    DXGI_FORMAT_BC2_UNORM                   = 74,
+    DXGI_FORMAT_BC2_UNORM_SRGB              = 75,
+    DXGI_FORMAT_BC3_TYPELESS                = 76,
+    DXGI_FORMAT_BC3_UNORM                   = 77,
+    DXGI_FORMAT_BC3_UNORM_SRGB              = 78,
+    DXGI_FORMAT_BC4_TYPELESS                = 79,
+    DXGI_FORMAT_BC4_UNORM                   = 80,
+    DXGI_FORMAT_BC4_SNORM                   = 81,
+    DXGI_FORMAT_BC5_TYPELESS                = 82,
+    DXGI_FORMAT_BC5_UNORM                   = 83,
+    DXGI_FORMAT_BC5_SNORM                   = 84,
+    DXGI_FORMAT_B5G6R5_UNORM                = 85,
+    DXGI_FORMAT_B8G8R8A8_UNORM              = 87,
+    DXGI_FORMAT_B8G8R8X8_UNORM              = 88,
+    DXGI_FORMAT_B8G8R8A8_TYPELESS           = 90,
+    DXGI_FORMAT_B8G8R8A8_UNORM_SRGB         = 91,
+    DXGI_FORMAT_B8G8R8X8_TYPELESS           = 92,
+    DXGI_FORMAT_B8G8R8X8_UNORM_SRGB         = 93,
+} DDSDXGIFormat;
+
+typedef struct DDSContext {
+    TextureDSPContext texdsp;
+    GetByteContext gbc;
+
+    int compressed;
+    int paletted;
+    enum DDSPostProc postproc;
+
+    const uint8_t *tex_data; // Compressed texture
+    int tex_ratio;           // Compression ratio
+
+    /* Pointer to the selected compress or decompress function. */
+    int (*tex_funct)(uint8_t *dst, ptrdiff_t stride, const uint8_t *block);
+} DDSContext;
+
+static int parse_pixel_format(AVCodecContext *avctx)
+{
+    DDSContext *ctx = avctx->priv_data;
+    GetByteContext *gbc = &ctx->gbc;
+    char buf[32];
+    uint32_t flags, fourcc, gimp_tag;
+    enum DDSDXGIFormat dxgi;
+    int size, bpp, r, g, b, a;
+    int alpha_exponent, ycocg_classic, ycocg_scaled, normal_map, array;
+
+    /* Alternative DDS implementations use reserved1 as custom header. */
+    bytestream2_skip(gbc, 4 * 3);
+    gimp_tag = bytestream2_get_le32(gbc);
+    alpha_exponent = gimp_tag == MKTAG('A', 'E', 'X', 'P');
+    ycocg_classic  = gimp_tag == MKTAG('Y', 'C', 'G', '1');
+    ycocg_scaled   = gimp_tag == MKTAG('Y', 'C', 'G', '2');
+    bytestream2_skip(gbc, 4 * 7);
+
+    /* Now the real DDPF starts. */
+    size = bytestream2_get_le32(gbc);
+    if (size != 32) {
+        av_log(avctx, AV_LOG_ERROR, "Invalid pixel format header %d.\n", size);
+        return AVERROR_INVALIDDATA;
+    }
+    flags = bytestream2_get_le32(gbc);
+    ctx->compressed = flags & DDPF_FOURCC;
+    ctx->paletted   = flags & DDPF_PALETTE;
+    normal_map      = flags & DDPF_NORMALMAP;
+    fourcc = bytestream2_get_le32(gbc);
+
+    bpp = bytestream2_get_le32(gbc); // rgbbitcount
+    r   = bytestream2_get_le32(gbc); // rbitmask
+    g   = bytestream2_get_le32(gbc); // gbitmask
+    b   = bytestream2_get_le32(gbc); // bbitmask
+    a   = bytestream2_get_le32(gbc); // abitmask
+
+    bytestream2_skip(gbc, 4); // caps
+    bytestream2_skip(gbc, 4); // caps2
+    bytestream2_skip(gbc, 4); // caps3
+    bytestream2_skip(gbc, 4); // caps4
+    bytestream2_skip(gbc, 4); // reserved2
+
+    av_get_codec_tag_string(buf, sizeof(buf), fourcc);
+    av_log(avctx, AV_LOG_VERBOSE, "fourcc %s bpp %d "
+           "r 0x%x g 0x%x b 0x%x a 0x%x\n", buf, bpp, r, g, b, a);
+    if (gimp_tag) {
+        av_get_codec_tag_string(buf, sizeof(buf), gimp_tag);
+        av_log(avctx, AV_LOG_VERBOSE, "and GIMP-DDS tag %s\n", buf);
+    }
+
+    if (ctx->compressed)
+        avctx->pix_fmt = AV_PIX_FMT_RGBA;
+
+    if (ctx->compressed) {
+        switch (fourcc) {
+        case MKTAG('D', 'X', 'T', '1'):
+            ctx->tex_ratio = 8;
+            ctx->tex_funct = ctx->texdsp.dxt1a_block;
+            break;
+        case MKTAG('D', 'X', 'T', '2'):
+            ctx->tex_ratio = 16;
+            ctx->tex_funct = ctx->texdsp.dxt2_block;
+            break;
+        case MKTAG('D', 'X', 'T', '3'):
+            ctx->tex_ratio = 16;
+            ctx->tex_funct = ctx->texdsp.dxt3_block;
+            break;
+        case MKTAG('D', 'X', 'T', '4'):
+            ctx->tex_ratio = 16;
+            ctx->tex_funct = ctx->texdsp.dxt4_block;
+            break;
+        case MKTAG('D', 'X', 'T', '5'):
+            ctx->tex_ratio = 16;
+            if (ycocg_scaled)
+                ctx->tex_funct = ctx->texdsp.dxt5ys_block;
+            else if (ycocg_classic)
+                ctx->tex_funct = ctx->texdsp.dxt5y_block;
+            else
+                ctx->tex_funct = ctx->texdsp.dxt5_block;
+            break;
+        case MKTAG('R', 'X', 'G', 'B'):
+            ctx->tex_ratio = 16;
+            ctx->tex_funct = ctx->texdsp.dxt5_block;
+            /* This format may be considered as a normal map,
+             * but it is handled differently in a separate postproc. */
+            ctx->postproc = DDS_SWIZZLE_RXGB;
+            normal_map = 0;
+            break;
+        case MKTAG('A', 'T', 'I', '1'):
+        case MKTAG('B', 'C', '4', 'U'):
+            ctx->tex_ratio = 8;
+            ctx->tex_funct = ctx->texdsp.rgtc1u_block;
+            break;
+        case MKTAG('B', 'C', '4', 'S'):
+            ctx->tex_ratio = 8;
+            ctx->tex_funct = ctx->texdsp.rgtc1s_block;
+            break;
+        case MKTAG('A', 'T', 'I', '2'):
+            /* RGT2 variant with swapped R and G (3Dc)*/
+            ctx->tex_ratio = 16;
+            ctx->tex_funct = ctx->texdsp.dxn3dc_block;
+            break;
+        case MKTAG('B', 'C', '5', 'U'):
+            ctx->tex_ratio = 16;
+            ctx->tex_funct = ctx->texdsp.rgtc2u_block;
+            break;
+        case MKTAG('B', 'C', '5', 'S'):
+            ctx->tex_ratio = 16;
+            ctx->tex_funct = ctx->texdsp.rgtc2s_block;
+            break;
+        case MKTAG('U', 'Y', 'V', 'Y'):
+            ctx->compressed = 0;
+            avctx->pix_fmt = AV_PIX_FMT_UYVY422;
+            break;
+        case MKTAG('Y', 'U', 'Y', '2'):
+            ctx->compressed = 0;
+            avctx->pix_fmt = AV_PIX_FMT_YUYV422;
+            break;
+        case MKTAG('P', '8', ' ', ' '):
+            /* ATI Palette8, same as normal palette */
+            ctx->compressed = 0;
+            ctx->paletted   = 1;
+            avctx->pix_fmt  = AV_PIX_FMT_PAL8;
+            break;
+        case MKTAG('D', 'X', '1', '0'):
+            /* DirectX 10 extra header */
+            dxgi = bytestream2_get_le32(gbc);
+            bytestream2_skip(gbc, 4); // resourceDimension
+            bytestream2_skip(gbc, 4); // miscFlag
+            array = bytestream2_get_le32(gbc);
+            bytestream2_skip(gbc, 4); // miscFlag2
+
+            if (array != 0)
+                av_log(avctx, AV_LOG_VERBOSE,
+                       "Found array of size %d (ignored).\n", array);
+
+            /* Only BC[1-5] are actually compressed. */
+            ctx->compressed = (dxgi >= 70) && (dxgi <= 84);
+
+            av_log(avctx, AV_LOG_VERBOSE, "DXGI format %d.\n", dxgi);
+            switch (dxgi) {
+            /* RGB types. */
+            case DXGI_FORMAT_R16G16B16A16_TYPELESS:
+            case DXGI_FORMAT_R16G16B16A16_FLOAT:
+            case DXGI_FORMAT_R16G16B16A16_UNORM:
+            case DXGI_FORMAT_R16G16B16A16_UINT:
+            case DXGI_FORMAT_R16G16B16A16_SNORM:
+            case DXGI_FORMAT_R16G16B16A16_SINT:
+                avctx->pix_fmt = AV_PIX_FMT_BGRA64;
+                break;
+            case DXGI_FORMAT_R8G8B8A8_UNORM_SRGB:
+                avctx->colorspace = AVCOL_SPC_RGB;
+            case DXGI_FORMAT_R8G8B8A8_TYPELESS:
+            case DXGI_FORMAT_R8G8B8A8_UNORM:
+            case DXGI_FORMAT_R8G8B8A8_UINT:
+            case DXGI_FORMAT_R8G8B8A8_SNORM:
+            case DXGI_FORMAT_R8G8B8A8_SINT:
+                avctx->pix_fmt = AV_PIX_FMT_BGRA;
+                break;
+            case DXGI_FORMAT_B8G8R8A8_UNORM_SRGB:
+                avctx->colorspace = AVCOL_SPC_RGB;
+            case DXGI_FORMAT_B8G8R8A8_TYPELESS:
+            case DXGI_FORMAT_B8G8R8A8_UNORM:
+                avctx->pix_fmt = AV_PIX_FMT_RGBA;
+                break;
+            case DXGI_FORMAT_B8G8R8X8_UNORM_SRGB:
+                avctx->colorspace = AVCOL_SPC_RGB;
+            case DXGI_FORMAT_B8G8R8X8_TYPELESS:
+            case DXGI_FORMAT_B8G8R8X8_UNORM:
+                avctx->pix_fmt = AV_PIX_FMT_RGBA; // opaque
+                break;
+            case DXGI_FORMAT_B5G6R5_UNORM:
+                avctx->pix_fmt = AV_PIX_FMT_RGB565LE;
+                break;
+            /* Texture types. */
+            case DXGI_FORMAT_BC1_UNORM_SRGB:
+                avctx->colorspace = AVCOL_SPC_RGB;
+            case DXGI_FORMAT_BC1_TYPELESS:
+            case DXGI_FORMAT_BC1_UNORM:
+                ctx->tex_ratio = 8;
+                ctx->tex_funct = ctx->texdsp.dxt1a_block;
+                break;
+            case DXGI_FORMAT_BC2_UNORM_SRGB:
+                avctx->colorspace = AVCOL_SPC_RGB;
+            case DXGI_FORMAT_BC2_TYPELESS:
+            case DXGI_FORMAT_BC2_UNORM:
+                ctx->tex_ratio = 16;
+                ctx->tex_funct = ctx->texdsp.dxt3_block;
+                break;
+            case DXGI_FORMAT_BC3_UNORM_SRGB:
+                avctx->colorspace = AVCOL_SPC_RGB;
+            case DXGI_FORMAT_BC3_TYPELESS:
+            case DXGI_FORMAT_BC3_UNORM:
+                ctx->tex_ratio = 16;
+                ctx->tex_funct = ctx->texdsp.dxt5_block;
+                break;
+            case DXGI_FORMAT_BC4_TYPELESS:
+            case DXGI_FORMAT_BC4_UNORM:
+                ctx->tex_ratio = 8;
+                ctx->tex_funct = ctx->texdsp.rgtc1u_block;
+                break;
+            case DXGI_FORMAT_BC4_SNORM:
+                ctx->tex_ratio = 8;
+                ctx->tex_funct = ctx->texdsp.rgtc1s_block;
+                break;
+            case DXGI_FORMAT_BC5_TYPELESS:
+            case DXGI_FORMAT_BC5_UNORM:
+                ctx->tex_ratio = 16;
+                ctx->tex_funct = ctx->texdsp.rgtc2u_block;
+                break;
+            case DXGI_FORMAT_BC5_SNORM:
+                ctx->tex_ratio = 16;
+                ctx->tex_funct = ctx->texdsp.rgtc2s_block;
+                break;
+            default:
+                av_log(avctx, AV_LOG_ERROR,
+                       "Unsupported DXGI format %d.\n", dxgi);
+                return AVERROR_INVALIDDATA;
+            }
+            break;
+        default:
+            av_log(avctx, AV_LOG_ERROR, "Unsupported %s fourcc.\n", buf);
+            return AVERROR_INVALIDDATA;
+        }
+    } else if (ctx->paletted) {
+        if (bpp == 8) {
+            avctx->pix_fmt = AV_PIX_FMT_PAL8;
+        } else {
+            av_log(avctx, AV_LOG_ERROR, "Unsupported palette bpp %d.\n", bpp);
+            return AVERROR_INVALIDDATA;
+        }
+    } else {
+        /*  8 bpp */
+        if (bpp == 8 && r == 0xff && g == 0 && b == 0 && a == 0)
+            avctx->pix_fmt = AV_PIX_FMT_GRAY8;
+        /* 16 bpp */
+        else if (bpp == 16 && r == 0xff && g == 0 && b == 0 && a == 0xff00)
+            avctx->pix_fmt = AV_PIX_FMT_YA8;
+        else if (bpp == 16 && r == 0xffff && g == 0 && b == 0 && a == 0)
+            avctx->pix_fmt = AV_PIX_FMT_GRAY16LE;
+        else if (bpp == 16 && r == 0xf800 && g == 0x7e0 && b == 0x1f && a == 0)
+            avctx->pix_fmt = AV_PIX_FMT_RGB565LE;
+        /* 24 bpp */
+        else if (bpp == 24 && r == 0xff0000 && g == 0xff00 && b == 0xff && a == 0)
+            avctx->pix_fmt = AV_PIX_FMT_BGR24;
+        /* 32 bpp */
+        else if (bpp == 32 && r == 0xff0000 && g == 0xff00 && b == 0xff && a == 0)
+            avctx->pix_fmt = AV_PIX_FMT_RGBA; // opaque
+        else if (bpp == 32 && r == 0xff && g == 0xff00 && b == 0xff0000 && a == 0)
+            avctx->pix_fmt = AV_PIX_FMT_BGRA; // opaque
+        else if (bpp == 32 && r == 0xff0000 && g == 0xff00 && b == 0xff && a == 0xff000000)
+            avctx->pix_fmt = AV_PIX_FMT_RGBA;
+        else if (bpp == 32 && r == 0xff && g == 0xff00 && b == 0xff0000 && a == 0xff000000)
+            avctx->pix_fmt = AV_PIX_FMT_BGRA;
+        /* give up */
+        else {
+            av_log(avctx, AV_LOG_ERROR, "Unknown pixel format "
+                   "[bpp %d r 0x%x g 0x%x b 0x%x a 0x%x].\n", bpp, r, g, b, a);
+            return AVERROR_INVALIDDATA;
+        }
+    }
+
+    /* Set any remaining post-proc that should happen before frame is ready. */
+    if (alpha_exponent)
+        ctx->postproc = DDS_ALPHA_EXP;
+    else if (normal_map)
+        ctx->postproc = DDS_NORMAL_MAP;
+    else if (ycocg_classic && !ctx->compressed)
+        ctx->postproc = DDS_RAW_YCOCG;
+    else if (avctx->pix_fmt == AV_PIX_FMT_YA8)
+        ctx->postproc = DDS_SWAP_ALPHA;
+
+    /* ATI/NVidia variants sometimes add swizzling in bpp. */
+    switch (bpp) {
+    case MKTAG('A', '2', 'X', 'Y'):
+        ctx->postproc = DDS_SWIZZLE_A2XY;
+        break;
+    case MKTAG('x', 'G', 'B', 'R'):
+        ctx->postproc = DDS_SWIZZLE_XGBR;
+        break;
+    case MKTAG('x', 'R', 'B', 'G'):
+        ctx->postproc = DDS_SWIZZLE_XRBG;
+        break;
+    case MKTAG('R', 'B', 'x', 'G'):
+        ctx->postproc = DDS_SWIZZLE_RBXG;
+        break;
+    case MKTAG('R', 'G', 'x', 'B'):
+        ctx->postproc = DDS_SWIZZLE_RGXB;
+        break;
+    case MKTAG('R', 'x', 'B', 'G'):
+        ctx->postproc = DDS_SWIZZLE_RXBG;
+        break;
+    case MKTAG('x', 'G', 'x', 'R'):
+        ctx->postproc = DDS_SWIZZLE_XGXR;
+        break;
+    case MKTAG('A', '2', 'D', '5'):
+        ctx->postproc = DDS_NORMAL_MAP;
+        break;
+    }
+
+    return 0;
+}
+
+static int decompress_texture_thread(AVCodecContext *avctx, void *arg,
+                                     int block_nb, int thread_nb)
+{
+    DDSContext *ctx = avctx->priv_data;
+    AVFrame *frame = arg;
+    int x = (TEXTURE_BLOCK_W * block_nb) % avctx->coded_width;
+    int y = TEXTURE_BLOCK_H * (TEXTURE_BLOCK_W * block_nb / avctx->coded_width);
+    uint8_t *p = frame->data[0] + x * 4 + y * frame->linesize[0];
+    const uint8_t *d = ctx->tex_data + block_nb * ctx->tex_ratio;
+
+    ctx->tex_funct(p, frame->linesize[0], d);
+    return 0;
+}
+
+static void do_swizzle(AVFrame *frame, int x, int y)
+{
+    int i;
+    for (i = 0; i < frame->linesize[0] * frame->height; i += 4) {
+        uint8_t *src = frame->data[0] + i;
+        FFSWAP(uint8_t, src[x], src[y]);
+    }
+}
+
+static void run_postproc(AVCodecContext *avctx, AVFrame *frame)
+{
+    DDSContext *ctx = avctx->priv_data;
+    int i, x_off;
+
+    switch (ctx->postproc) {
+    case DDS_ALPHA_EXP:
+        /* Alpha-exponential mode divides each channel by the maximum
+         * R, G or B value, and stores the multiplying factor in the
+         * alpha channel. */
+        av_log(avctx, AV_LOG_DEBUG, "Post-processing alpha exponent.\n");
+
+        for (i = 0; i < frame->linesize[0] * frame->height; i += 4) {
+            uint8_t *src = frame->data[0] + i;
+            int r = src[0];
+            int g = src[1];
+            int b = src[2];
+            int a = src[3];
+
+            src[0] = r * a / 255;
+            src[1] = g * a / 255;
+            src[2] = b * a / 255;
+            src[3] = 255;
+        }
+        break;
+    case DDS_NORMAL_MAP:
+        /* Normal maps work in the XYZ color space and they encode
+         * X in R or in A, depending on the texture type, Y in G and
+         * derive Z with a square root of the distance.
+         *
+         * http://www.realtimecollisiondetection.net/blog/?p=28 */
+        av_log(avctx, AV_LOG_DEBUG, "Post-processing normal map.\n");
+
+        x_off = ctx->tex_ratio == 8 ? 0 : 3;
+        for (i = 0; i < frame->linesize[0] * frame->height; i += 4) {
+            uint8_t *src = frame->data[0] + i;
+            int x = src[x_off];
+            int y = src[1];
+            int z = 127;
+
+            int d = (255 * 255 - x * x - y * y) / 2;
+            if (d > 0)
+                z = rint(sqrtf(d));
+
+            src[0] = x;
+            src[1] = y;
+            src[2] = z;
+            src[3] = 255;
+        }
+        break;
+    case DDS_RAW_YCOCG:
+        /* Data is Y-Co-Cg-A and not RGBA, but they are represented
+         * with the same masks in the DDPF header. */
+        av_log(avctx, AV_LOG_DEBUG, "Post-processing raw YCoCg.\n");
+
+        for (i = 0; i < frame->linesize[0] * frame->height; i += 4) {
+            uint8_t *src = frame->data[0] + i;
+            int a  = src[0];
+            int cg = src[1] - 128;
+            int co = src[2] - 128;
+            int y  = src[3];
+
+            src[0] = av_clip_uint8(y + co - cg);
+            src[1] = av_clip_uint8(y + cg);
+            src[2] = av_clip_uint8(y - co - cg);
+            src[3] = a;
+        }
+        break;
+    case DDS_SWAP_ALPHA:
+        /* Alpha and Luma are stored swapped. */
+        av_log(avctx, AV_LOG_DEBUG, "Post-processing swapped Luma/Alpha.\n");
+
+        for (i = 0; i < frame->linesize[0] * frame->height; i += 2) {
+            uint8_t *src = frame->data[0] + i;
+            FFSWAP(uint8_t, src[0], src[1]);
+        }
+        break;
+    case DDS_SWIZZLE_A2XY:
+        /* Swap R and G, often used to restore a standard RGTC2. */
+        av_log(avctx, AV_LOG_DEBUG, "Post-processing A2XY swizzle.\n");
+        do_swizzle(frame, 0, 1);
+        break;
+    case DDS_SWIZZLE_RBXG:
+        /* Swap G and A, then B and new A (G). */
+        av_log(avctx, AV_LOG_DEBUG, "Post-processing RBXG swizzle.\n");
+        do_swizzle(frame, 1, 3);
+        do_swizzle(frame, 2, 3);
+        break;
+    case DDS_SWIZZLE_RGXB:
+        /* Swap B and A. */
+        av_log(avctx, AV_LOG_DEBUG, "Post-processing RGXB swizzle.\n");
+        do_swizzle(frame, 2, 3);
+        break;
+    case DDS_SWIZZLE_RXBG:
+        /* Swap G and A. */
+        av_log(avctx, AV_LOG_DEBUG, "Post-processing RXBG swizzle.\n");
+        do_swizzle(frame, 1, 3);
+        break;
+    case DDS_SWIZZLE_RXGB:
+        /* Swap R and A (misleading name). */
+        av_log(avctx, AV_LOG_DEBUG, "Post-processing RXGB swizzle.\n");
+        do_swizzle(frame, 0, 3);
+        break;
+    case DDS_SWIZZLE_XGBR:
+        /* Swap B and A, then R and new A (B). */
+        av_log(avctx, AV_LOG_DEBUG, "Post-processing XGBR swizzle.\n");
+        do_swizzle(frame, 2, 3);
+        do_swizzle(frame, 0, 3);
+        break;
+    case DDS_SWIZZLE_XGXR:
+        /* Swap G and A, then R and new A (G), then new R (G) and new G (A).
+         * This variant does not store any B component. */
+        av_log(avctx, AV_LOG_DEBUG, "Post-processing XGXR swizzle.\n");
+        do_swizzle(frame, 1, 3);
+        do_swizzle(frame, 0, 3);
+        do_swizzle(frame, 0, 1);
+        break;
+    case DDS_SWIZZLE_XRBG:
+        /* Swap G and A, then R and new A (G). */
+        av_log(avctx, AV_LOG_DEBUG, "Post-processing XRBG swizzle.\n");
+        do_swizzle(frame, 1, 3);
+        do_swizzle(frame, 0, 3);
+        break;
+    }
+}
+
+static int dds_decode(AVCodecContext *avctx, void *data,
+                      int *got_frame, AVPacket *avpkt)
+{
+    DDSContext *ctx = avctx->priv_data;
+    GetByteContext *gbc = &ctx->gbc;
+    AVFrame *frame = data;
+    int blocks, mipmap;
+    int ret;
+
+    ff_texturedsp_init(&ctx->texdsp);
+    bytestream2_init(gbc, avpkt->data, avpkt->size);
+
+    if (bytestream2_get_bytes_left(gbc) < 128) {
+        av_log(avctx, AV_LOG_ERROR, "Frame is too small (%d).",
+               bytestream2_get_bytes_left(gbc));
+        return AVERROR_INVALIDDATA;
+    }
+
+    if (bytestream2_get_le32(gbc) != MKTAG('D', 'D', 'S', ' ') ||
+        bytestream2_get_le32(gbc) != 124) { // header size
+        av_log(avctx, AV_LOG_ERROR, "Invalid DDS header.");
+        return AVERROR_INVALIDDATA;
+    }
+
+    bytestream2_skip(gbc, 4); // flags
+
+    avctx->height = bytestream2_get_le32(gbc);
+    avctx->width  = bytestream2_get_le32(gbc);
+    ret = av_image_check_size(avctx->width, avctx->height, 0, avctx);
+    if (ret < 0) {
+        av_log(avctx, AV_LOG_ERROR, "Invalid image size %dx%d.\n",
+               avctx->width, avctx->height);
+        return ret;
+    }
+
+    /* Since codec is based on 4x4 blocks, size is aligned to 4. */
+    avctx->coded_width  = FFALIGN(avctx->width,  TEXTURE_BLOCK_W);
+    avctx->coded_height = FFALIGN(avctx->height, TEXTURE_BLOCK_H);
+
+    bytestream2_skip(gbc, 4); // pitch
+    bytestream2_skip(gbc, 4); // depth
+    mipmap = bytestream2_get_le32(gbc);
+    if (mipmap != 0)
+        av_log(avctx, AV_LOG_VERBOSE, "Found %d mipmaps (ignored).\n", mipmap);
+
+    /* Extract pixel format information, considering additional elements
+     * in reserved1 and reserved2. */
+    ret = parse_pixel_format(avctx);
+    if (ret < 0)
+        return ret;
+
+    ret = ff_get_buffer(avctx, frame, 0);
+    if (ret < 0)
+        return ret;
+
+    if (ctx->compressed) {
+        /* Use the decompress function on the texture, one block per thread. */
+        ctx->tex_data = gbc->buffer;
+        blocks = avctx->coded_width * avctx->coded_height / (TEXTURE_BLOCK_W * TEXTURE_BLOCK_H);
+        avctx->execute2(avctx, decompress_texture_thread, frame, NULL, blocks);
+    } else {
+        int linesize = av_image_get_linesize(avctx->pix_fmt, frame->width, 0);
+
+        if (ctx->paletted) {
+            /* Use the first 1024 bytes as palette, then copy the rest. */
+            bytestream2_get_buffer(gbc, frame->data[1], 256 * 4);
+            frame->palette_has_changed = 1;
+        }
+
+        av_image_copy_plane(frame->data[0], frame->linesize[0],
+                            gbc->buffer, linesize,
+                            linesize, frame->height);
+    }
+
+    /* Run any post processing here if needed. */
+    if (avctx->pix_fmt == AV_PIX_FMT_RGBA || avctx->pix_fmt == AV_PIX_FMT_YA8)
+        run_postproc(avctx, frame);
+
+    /* Frame is ready to be output. */
+    frame->pict_type = AV_PICTURE_TYPE_I;
+    frame->key_frame = 1;
+    *got_frame = 1;
+
+    return avpkt->size;
+}
+
+AVCodec ff_dds_decoder = {
+    .name           = "dds",
+    .long_name      = NULL_IF_CONFIG_SMALL("DirectDraw Surface image decoder"),
+    .type           = AVMEDIA_TYPE_VIDEO,
+    .id             = AV_CODEC_ID_DDS,
+    .decode         = dds_decode,
+    .priv_data_size = sizeof(DDSContext),
+    .capabilities   = CODEC_CAP_DR1 | CODEC_CAP_SLICE_THREADS,
+    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE
+};