video: separate repacking code from zimg and make it independent

For whatever purpose. If anything, this makes the zimg wrapper cleaner.

The added tests are not particular exhaustive, but nice to have. This
also makes the scale_zimg.c test pretty useless, because it only tests
repacking (going through the zimg wrapper). In theory, the repack_tests
things could also be used on scalers, but I guess it doesn't matter.

Some things are added over the previous zimg wrapper code. For example,
some fringe formats can now be expanded to 8 bit per component for
convenience.

4 files changed, 1244 insertions, 895 deletions

diff --git a/video/img_format.h b/video/img_format.h
index 8e55cc9493..b0fdef8a50 100644
--- a/video/img_format.h
+++ b/video/img_format.h
@@ -69,8 +69,9 @@ struct mp_imgfmt_desc {
     int flags;              // MP_IMGFLAG_* bitfield
     int8_t num_planes;
     int8_t chroma_xs, chroma_ys; // chroma shift (i.e. log2 of chroma pixel size)
-    int8_t align_x, align_y;     // pixel size to get byte alignment and to get
+    int8_t align_x, align_y;     // pixel count to get byte alignment and to get
                                  // to a pixel pos where luma & chroma aligns
+                                 // always power of 2
     int8_t bytes[MP_MAX_PLANES]; // bytes per pixel (MP_IMGFLAG_BYTE_ALIGNED)
     int8_t bpp[MP_MAX_PLANES];   // bits per pixel
     int8_t plane_bits;           // number of bits in use for plane 0
diff --git a/video/repack.c b/video/repack.c
new file mode 100644
index 0000000000..359e32996d
--- /dev/null
+++ b/video/repack.c
@@ -0,0 +1,1110 @@
+/*
+ * This file is part of mpv.
+ *
+ * mpv 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.
+ *
+ * mpv 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 mpv.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <math.h>
+
+#include <libavutil/bswap.h>
+#include <libavutil/pixfmt.h>
+
+#include "common/common.h"
+#include "repack.h"
+#include "video/fmt-conversion.h"
+#include "video/img_format.h"
+#include "video/mp_image.h"
+
+enum repack_step_type {
+    REPACK_STEP_REPACK,
+    REPACK_STEP_ENDIAN,
+};
+
+struct repack_step {
+    enum repack_step_type type;
+    // 0=input, 1=output
+    struct mp_image *buf[2];
+    bool user_buf[2]; // user_buf[n]==true if buf[n] = user src/dst buffer
+    struct mp_imgfmt_desc fmt[2];
+    struct mp_image *tmp; // output buffer, if needed
+};
+
+struct mp_repack {
+    bool pack;                  // if false, this is for unpacking
+    int flags;
+    int imgfmt_user;            // original mp format (unchanged endian)
+    int imgfmt_a;               // original mp format (possibly packed format,
+                                // swapped endian)
+    int imgfmt_b;               // equivalent unpacked/planar format
+    struct mp_imgfmt_desc fmt_a;// ==imgfmt_a
+    struct mp_imgfmt_desc fmt_b;// ==imgfmt_b
+
+    void (*repack)(struct mp_repack *rp,
+                   struct mp_image *a, int a_x, int a_y,
+                   struct mp_image *b, int b_x, int b_y, int w);
+
+    bool passthrough_y;         // possible luma plane optimization for e.g. nv12
+    int endian_size;            // endian swap; 0=none, 2/4=swap word size
+
+    // For packed_repack.
+    int components[4];          // b[n] = mp_image.planes[components[n]]
+    //  pack:   a is dst, b is src
+    //  unpack: a is src, b is dst
+    void (*packed_repack_scanline)(void *a, void *b[], int w);
+
+    // Fringe RGB/YUV.
+    uint8_t comp_size;
+    uint8_t *comp_map;
+    uint8_t comp_shifts[3];
+    uint8_t *comp_lut;
+
+    // REPACK_STEP_REPACK: if true, need to copy this plane
+    bool copy_buf[4];
+
+    struct repack_step steps[4];
+    int num_steps;
+
+    bool configured;
+};
+
+// depth = number of LSB in use
+static int find_gbrp_format(int depth, int num_planes)
+{
+    if (num_planes != 3 && num_planes != 4)
+        return 0;
+    struct mp_regular_imgfmt desc = {
+        .component_type = MP_COMPONENT_TYPE_UINT,
+        .forced_csp = MP_CSP_RGB,
+        .component_size = depth > 8 ? 2 : 1,
+        .component_pad = depth - (depth > 8 ? 16 : 8),
+        .num_planes = num_planes,
+        .planes = { {1, {2}}, {1, {3}}, {1, {1}}, {1, {4}} },
+    };
+    return mp_find_regular_imgfmt(&desc);
+}
+
+// depth = number of LSB in use
+static int find_yuv_format(int depth, int num_planes)
+{
+    if (num_planes < 1 || num_planes > 4)
+        return 0;
+    struct mp_regular_imgfmt desc = {
+        .component_type = MP_COMPONENT_TYPE_UINT,
+        .component_size = depth > 8 ? 2 : 1,
+        .component_pad = depth - (depth > 8 ? 16 : 8),
+        .num_planes = num_planes,
+        .planes = { {1, {1}}, {1, {2}}, {1, {3}}, {1, {4}} },
+    };
+    if (num_planes == 2)
+        desc.planes[1].components[0] = 4;
+    return mp_find_regular_imgfmt(&desc);
+}
+
+// Copy one line on the plane p.
+static void copy_plane(struct mp_image *dst, int dst_x, int dst_y,
+                       struct mp_image *src, int src_x, int src_y,
+                       int w, int p)
+{
+    // Number of lines on this plane.
+    int h = (1 << dst->fmt.chroma_ys) - (1 << dst->fmt.ys[p]) + 1;
+    size_t size = mp_image_plane_bytes(dst, p, dst_x, w);
+
+    assert(dst->fmt.bpp[p] == src->fmt.bpp[p]);
+
+    for (int y = 0; y < h; y++) {
+        void *pd = mp_image_pixel_ptr(dst, p, dst_x, dst_y + y);
+        void *ps = mp_image_pixel_ptr(src, p, src_x, src_y + y);
+        memcpy(pd, ps, size);
+    }
+}
+
+// Swap endian for one line.
+static void swap_endian(struct mp_image *dst, int dst_x, int dst_y,
+                        struct mp_image *src, int src_x, int src_y,
+                        int w, int endian_size)
+{
+    assert(src->fmt.num_planes == dst->fmt.num_planes);
+
+    for (int p = 0; p < dst->fmt.num_planes; p++) {
+        int xs = dst->fmt.xs[p];
+        int bpp = dst->fmt.bytes[p];
+        int words_per_pixel = bpp / endian_size;
+        int num_words = ((w + (1 << xs) - 1) >> xs) * words_per_pixel;
+        // Number of lines on this plane.
+        int h = (1 << dst->fmt.chroma_ys) - (1 << dst->fmt.ys[p]) + 1;
+
+        assert(src->fmt.bytes[p] == bpp);
+
+        for (int y = 0; y < h; y++) {
+            void *s = mp_image_pixel_ptr(src, p, src_x, src_y + y);
+            void *d = mp_image_pixel_ptr(dst, p, dst_x, dst_y + y);
+            switch (endian_size) {
+            case 2:
+                for (int x = 0; x < num_words; x++)
+                    ((uint16_t *)d)[x] = av_bswap16(((uint16_t *)s)[x]);
+                break;
+            case 4:
+                for (int x = 0; x < num_words; x++)
+                    ((uint32_t *)d)[x] = av_bswap32(((uint32_t *)s)[x]);
+                break;
+            default:
+                assert(0);
+            }
+        }
+    }
+}
+
+// PA = PAck, copy planar input to single packed array
+// UN = UNpack, copy packed input to planar output
+// Naming convention:
+//  pa_/un_ prefix to identify conversion direction.
+//  Left (LSB, lowest byte address) -> Right (MSB, highest byte address).
+//      (This is unusual; MSB to LSB is more commonly used to describe formats,
+//       but our convention makes more sense for byte access in little endian.)
+//  "c" identifies a color component.
+//  "z" identifies known zero padding.
+//  "x" identifies uninitialized padding.
+//  A component is followed by its size in bits.
+//  Size can be omitted for multiple uniform components (c8c8c8 == ccc8).
+// Unpackers will often use "x" for padding, because they ignore it, while
+// packers will use "z" because they write zero.
+
+#define PA_WORD_4(name, packed_t, plane_t, sh_c0, sh_c1, sh_c2, sh_c3)      \
+    static void name(void *dst, void *src[], int w) {                       \
+        for (int x = 0; x < w; x++) {                                       \
+            ((packed_t *)dst)[x] =                                          \
+                ((packed_t)((plane_t *)src[0])[x] << (sh_c0)) |             \
+                ((packed_t)((plane_t *)src[1])[x] << (sh_c1)) |             \
+                ((packed_t)((plane_t *)src[2])[x] << (sh_c2)) |             \
+                ((packed_t)((plane_t *)src[3])[x] << (sh_c3));              \
+        }                                                                   \
+    }
+
+#define UN_WORD_4(name, packed_t, plane_t, sh_c0, sh_c1, sh_c2, sh_c3, mask)\
+    static void name(void *src, void *dst[], int w) {                       \
+        for (int x = 0; x < w; x++) {                                       \
+            packed_t c = ((packed_t *)src)[x];                              \
+            ((plane_t *)dst[0])[x] = (c >> (sh_c0)) & (mask);               \
+            ((plane_t *)dst[1])[x] = (c >> (sh_c1)) & (mask);               \
+            ((plane_t *)dst[2])[x] = (c >> (sh_c2)) & (mask);               \
+            ((plane_t *)dst[3])[x] = (c >> (sh_c3)) & (mask);               \
+        }                                                                   \
+    }
+
+
+#define PA_WORD_3(name, packed_t, plane_t, sh_c0, sh_c1, sh_c2, pad)        \
+    static void name(void *dst, void *src[], int w) {                       \
+        for (int x = 0; x < w; x++) {                                       \
+            ((packed_t *)dst)[x] = (pad) |                                  \
+                ((packed_t)((plane_t *)src[0])[x] << (sh_c0)) |             \
+                ((packed_t)((plane_t *)src[1])[x] << (sh_c1)) |             \
+                ((packed_t)((plane_t *)src[2])[x] << (sh_c2));              \
+        }                                                                   \
+    }
+
+UN_WORD_4(un_cccc8,  uint32_t, uint8_t,  0, 8,  16, 24, 0xFFu)
+PA_WORD_4(pa_cccc8,  uint32_t, uint8_t,  0, 8,  16, 24)
+// Not sure if this is a good idea; there may be no alignment guarantee.
+UN_WORD_4(un_cccc16,  uint64_t, uint16_t,  0, 16,  32, 48, 0xFFFFu)
+PA_WORD_4(pa_cccc16,  uint64_t, uint16_t,  0, 16,  32, 48)
+
+#define UN_WORD_3(name, packed_t, plane_t, sh_c0, sh_c1, sh_c2, mask)       \
+    static void name(void *src, void *dst[], int w) {                       \
+        for (int x = 0; x < w; x++) {                                       \
+            packed_t c = ((packed_t *)src)[x];                              \
+            ((plane_t *)dst[0])[x] = (c >> (sh_c0)) & (mask);               \
+            ((plane_t *)dst[1])[x] = (c >> (sh_c1)) & (mask);               \
+            ((plane_t *)dst[2])[x] = (c >> (sh_c2)) & (mask);               \
+        }                                                                   \
+    }
+
+UN_WORD_3(un_ccc8x8,  uint32_t, uint8_t,  0, 8,  16, 0xFFu)
+PA_WORD_3(pa_ccc8z8,  uint32_t, uint8_t,  0, 8,  16, 0)
+UN_WORD_3(un_x8ccc8,  uint32_t, uint8_t,  8, 16, 24, 0xFFu)
+PA_WORD_3(pa_z8ccc8,  uint32_t, uint8_t,  8, 16, 24, 0)
+UN_WORD_3(un_ccc10x2, uint32_t, uint16_t, 0, 10, 20, 0x3FFu)
+PA_WORD_3(pa_ccc10z2, uint32_t, uint16_t, 20, 10, 0, 0)
+
+#define PA_WORD_2(name, packed_t, plane_t, sh_c0, sh_c1, pad)               \
+    static void name(void *dst, void *src[], int w) {                       \
+        for (int x = 0; x < w; x++) {                                       \
+            ((packed_t *)dst)[x] = (pad) |                                  \
+                ((packed_t)((plane_t *)src[0])[x] << (sh_c0)) |             \
+                ((packed_t)((plane_t *)src[1])[x] << (sh_c1));              \
+        }                                                                   \
+    }
+
+#define UN_WORD_2(name, packed_t, plane_t, sh_c0, sh_c1, mask)              \
+    static void name(void *src, void *dst[], int w) {                       \
+        for (int x = 0; x < w; x++) {                                       \
+            packed_t c = ((packed_t *)src)[x];                              \
+            ((plane_t *)dst[0])[x] = (c >> (sh_c0)) & (mask);               \
+            ((plane_t *)dst[1])[x] = (c >> (sh_c1)) & (mask);               \
+        }                                                                   \
+    }
+
+UN_WORD_2(un_cc8,  uint16_t, uint8_t,  0, 8,  0xFFu)
+PA_WORD_2(pa_cc8,  uint16_t, uint8_t,  0, 8,  0)
+UN_WORD_2(un_cc16, uint32_t, uint16_t, 0, 16, 0xFFFFu)
+PA_WORD_2(pa_cc16, uint32_t, uint16_t, 0, 16, 0)
+
+#define PA_SEQ_3(name, comp_t)                                              \
+    static void name(void *dst, void *src[], int w) {                       \
+        comp_t *r = dst;                                                    \
+        for (int x = 0; x < w; x++) {                                       \
+            *r++ = ((comp_t *)src[0])[x];                                   \
+            *r++ = ((comp_t *)src[1])[x];                                   \
+            *r++ = ((comp_t *)src[2])[x];                                   \
+        }                                                                   \
+    }
+
+#define UN_SEQ_3(name, comp_t)                                              \
+    static void name(void *src, void *dst[], int w) {                       \
+        comp_t *r = src;                                                    \
+        for (int x = 0; x < w; x++) {                                       \
+            ((comp_t *)dst[0])[x] = *r++;                                   \
+            ((comp_t *)dst[1])[x] = *r++;                                   \
+            ((comp_t *)dst[2])[x] = *r++;                                   \
+        }                                                                   \
+    }
+
+UN_SEQ_3(un_ccc8,  uint8_t)
+PA_SEQ_3(pa_ccc8,  uint8_t)
+UN_SEQ_3(un_ccc16, uint16_t)
+PA_SEQ_3(pa_ccc16, uint16_t)
+
+// "regular": single packed plane, all components have same width (except padding)
+struct regular_repacker {
+    int packed_width;       // number of bits of the packed pixel
+    int component_width;    // number of bits for a single component
+    int prepadding;         // number of bits of LSB padding
+    int num_components;     // number of components that can be accessed
+    void (*pa_scanline)(void *a, void *b[], int w);
+    void (*un_scanline)(void *a, void *b[], int w);
+};
+
+static const struct regular_repacker regular_repackers[] = {
+    {32, 8,  0, 3, pa_ccc8z8,  un_ccc8x8},
+    {32, 8,  8, 3, pa_z8ccc8,  un_x8ccc8},
+    {32, 8,  0, 4, pa_cccc8,   un_cccc8},
+    {64, 16, 0, 4, pa_cccc16,  un_cccc16},
+    {24, 8,  0, 3, pa_ccc8,    un_ccc8},
+    {48, 16, 0, 3, pa_ccc16,   un_ccc16},
+    {16, 8,  0, 2, pa_cc8,     un_cc8},
+    {32, 16, 0, 2, pa_cc16,    un_cc16},
+    {32, 10, 0, 3, pa_ccc10z2, un_ccc10x2},
+};
+
+static void packed_repack(struct mp_repack *rp,
+                          struct mp_image *a, int a_x, int a_y,
+                          struct mp_image *b, int b_x, int b_y, int w)
+{
+    uint32_t *pa = mp_image_pixel_ptr(a, 0, a_x, a_y);
+
+    void *pb[4] = {0};
+    for (int p = 0; p < b->num_planes; p++) {
+        int s = rp->components[p];
+        pb[p] = mp_image_pixel_ptr(b, s, b_x, b_y);
+    }
+
+    rp->packed_repack_scanline(pa, pb, w);
+}
+
+// Tries to set a packer/unpacker for component-wise byte aligned formats.
+static void setup_packed_packer(struct mp_repack *rp)
+{
+    struct mp_regular_imgfmt desc;
+    if (!mp_get_regular_imgfmt(&desc, rp->imgfmt_a))
+        return;
+
+    if (desc.num_planes != 1 || desc.planes[0].num_components < 2)
+        return;
+    struct mp_regular_imgfmt_plane *p = &desc.planes[0];
+
+    int num_real_components = 0;
+    bool has_alpha = false;
+    for (int n = 0; n < p->num_components; n++) {
+        if (p->components[n]) {
+            has_alpha |= p->components[n] == 4;
+            num_real_components += 1;
+        } else {
+            // padding must be in MSB or LSB
+            if (n != 0 && n != p->num_components - 1)
+                return;
+        }
+    }
+
+    int depth = desc.component_size * 8 + MPMIN(0, desc.component_pad);
+
+    static const int reorder_gbrp[] = {0, 3, 1, 2, 4};
+    static const int reorder_yuv[] = {0, 1, 2, 3, 4};
+    int planar_fmt = 0;
+    const int *reorder = NULL;
+    if (desc.forced_csp) {
+        if (desc.forced_csp != MP_CSP_RGB && desc.forced_csp != MP_CSP_XYZ)
+            return;
+        planar_fmt = find_gbrp_format(depth, num_real_components);
+        reorder = reorder_gbrp;
+    } else {
+        planar_fmt = find_yuv_format(depth, num_real_components);
+        reorder = reorder_yuv;
+    }
+    if (!planar_fmt)
+        return;
+
+    for (int i = 0; i < MP_ARRAY_SIZE(regular_repackers); i++) {
+        const struct regular_repacker *pa = &regular_repackers[i];
+
+        // The following may assume little endian (because some repack backends
+        // use word access, while the metadata here uses byte access).
+
+        int prepad = p->components[0] ? 0 : 8;
+        int first_comp = p->components[0] ? 0 : 1;
+        void (*repack_cb)(void *pa, void *pb[], int w) =
+            rp->pack ? pa->pa_scanline : pa->un_scanline;
+
+        if (pa->packed_width != desc.component_size * p->num_components * 8 ||
+            pa->component_width != depth ||
+            pa->num_components != num_real_components ||
+            pa->prepadding != prepad ||
+            !repack_cb)
+            continue;
+
+        rp->repack = packed_repack;
+        rp->packed_repack_scanline = repack_cb;
+        rp->imgfmt_b = planar_fmt;
+        for (int n = 0; n < num_real_components; n++) {
+            // Determine permutation that maps component order between the two
+            // formats, with has_alpha special case (see above).
+            int c = reorder[p->components[first_comp + n]];
+            rp->components[n] = c == 4 ? num_real_components - 1 : c - 1;
+        }
+        return;
+    }
+}
+
+struct fringe_rgb_repacker {
+    // To avoid making a mess of IMGFMT_*, we use av formats directly.
+    enum AVPixelFormat avfmt;
+    // If true, use BGR instead of RGB.
+    //  False:  LSB - R - G - B - pad - MSB
+    //  True:   LSB - B - G - R - pad - MSB
+    bool rev_order;
+    // Size in bit for each component, strictly from LSB to MSB.
+    int bits[3];
+    bool be;
+};
+
+static const struct fringe_rgb_repacker fringe_rgb_repackers[] = {
+    {AV_PIX_FMT_BGR4_BYTE,  false,  {1, 2, 1}},
+    {AV_PIX_FMT_RGB4_BYTE,  true,   {1, 2, 1}},
+    {AV_PIX_FMT_BGR8,       false,  {3, 3, 2}},
+    {AV_PIX_FMT_RGB8,       true,   {2, 3, 3}}, // pixdesc desc. and doc. bug?
+    {AV_PIX_FMT_RGB444LE,   true,   {4, 4, 4}},
+    {AV_PIX_FMT_RGB444BE,   true,   {4, 4, 4}, .be = true},
+    {AV_PIX_FMT_BGR444LE,   false,  {4, 4, 4}},
+    {AV_PIX_FMT_BGR444BE,   false,  {4, 4, 4}, .be = true},
+    {AV_PIX_FMT_BGR565LE,   false,  {5, 6, 5}},
+    {AV_PIX_FMT_BGR565BE,   false,  {5, 6, 5}, .be = true},
+    {AV_PIX_FMT_RGB565LE,   true,   {5, 6, 5}},
+    {AV_PIX_FMT_RGB565BE,   true,   {5, 6, 5}, .be = true},
+    {AV_PIX_FMT_BGR555LE,   false,  {5, 5, 5}},
+    {AV_PIX_FMT_BGR555BE,   false,  {5, 5, 5}, .be = true},
+    {AV_PIX_FMT_RGB555LE,   true,   {5, 5, 5}},
+    {AV_PIX_FMT_RGB555BE,   true,   {5, 5, 5}, .be = true},
+};
+
+#define PA_SHIFT_LUT8(name, packed_t)                                       \
+    static void name(void *dst, void *src[], int w, uint8_t *lut,           \
+                     uint8_t s0, uint8_t s1, uint8_t s2) {                  \
+        for (int x = 0; x < w; x++) {                                       \
+            ((packed_t *)dst)[x] =                                          \
+                (lut[((uint8_t *)src[0])[x] + 256 * 0] << s0) |             \
+                (lut[((uint8_t *)src[1])[x] + 256 * 1] << s1) |             \
+                (lut[((uint8_t *)src[2])[x] + 256 * 2] << s2);              \
+        }                                                                   \
+    }
+
+
+#define UN_SHIFT_LUT8(name, packed_t)                                       \
+    static void name(void *src, void *dst[], int w, uint8_t *lut,           \
+                     uint8_t s0, uint8_t s1, uint8_t s2) {                  \
+        for (int x = 0; x < w; x++) {                                       \
+            packed_t c = ((packed_t *)src)[x];                              \
+            ((uint8_t *)dst[0])[x] = lut[((c >> s0) & 0xFF) + 256 * 0];     \
+            ((uint8_t *)dst[1])[x] = lut[((c >> s1) & 0xFF) + 256 * 1];     \
+            ((uint8_t *)dst[2])[x] = lut[((c >> s2) & 0xFF) + 256 * 2];     \
+        }                                                                   \
+    }
+
+PA_SHIFT_LUT8(pa_shift_lut8_8,  uint8_t)
+PA_SHIFT_LUT8(pa_shift_lut8_16, uint16_t)
+UN_SHIFT_LUT8(un_shift_lut8_8,  uint8_t)
+UN_SHIFT_LUT8(un_shift_lut8_16, uint16_t)
+
+static void fringe_rgb_repack(struct mp_repack *rp,
+                              struct mp_image *a, int a_x, int a_y,
+                              struct mp_image *b, int b_x, int b_y, int w)
+{
+    void *pa = mp_image_pixel_ptr(a, 0, a_x, a_y);
+
+    void *pb[4] = {0};
+    for (int p = 0; p < b->num_planes; p++) {
+        int s = rp->components[p];
+        pb[p] = mp_image_pixel_ptr(b, s, b_x, b_y);
+    }
+
+    assert(rp->comp_size == 1 || rp->comp_size == 2);
+
+    void (*repack)(void *pa, void *pb[], int w, uint8_t *lut,
+                   uint8_t s0, uint8_t s1, uint8_t s2) = NULL;
+    if (rp->pack) {
+        repack = rp->comp_size == 1 ? pa_shift_lut8_8 : pa_shift_lut8_16;
+    } else {
+        repack = rp->comp_size == 1 ? un_shift_lut8_8 : un_shift_lut8_16;
+    }
+    repack(pa, pb, w, rp->comp_lut,
+           rp->comp_shifts[0], rp->comp_shifts[1], rp->comp_shifts[2]);
+}
+
+static void setup_fringe_rgb_packer(struct mp_repack *rp)
+{
+    enum AVPixelFormat avfmt = imgfmt2pixfmt(rp->imgfmt_a);
+
+    const struct fringe_rgb_repacker *fmt = NULL;
+    for (int n = 0; n < MP_ARRAY_SIZE(fringe_rgb_repackers); n++) {
+        if (fringe_rgb_repackers[n].avfmt == avfmt) {
+            fmt = &fringe_rgb_repackers[n];
+            break;
+        }
+    }
+
+    if (!fmt)
+        return;
+
+    int depth = fmt->bits[0];
+    for (int n = 0; n < 3; n++) {
+        if (rp->flags & REPACK_CREATE_ROUND_DOWN) {
+            depth = MPMIN(depth, fmt->bits[n]);
+        } else {
+            depth = MPMAX(depth, fmt->bits[n]);
+        }
+    }
+    if (rp->flags & REPACK_CREATE_EXPAND_8BIT)
+        depth = 8;
+
+    rp->imgfmt_b = find_gbrp_format(depth, 3);
+    if (!rp->imgfmt_b)
+        return;
+    rp->comp_lut = talloc_array(rp, uint8_t, 256 * 3);
+    rp->repack = fringe_rgb_repack;
+    static const int c_order_rgb[] = {3, 1, 2};
+    static const int c_order_bgr[] = {2, 1, 3};
+    for (int n = 0; n < 3; n++)
+        rp->components[n] = (fmt->rev_order ? c_order_bgr : c_order_rgb)[n] - 1;
+
+    int bitpos = 0;
+    for (int n = 0; n < 3; n++) {
+        int bits = fmt->bits[n];
+        rp->comp_shifts[n] = bitpos;
+        if (rp->comp_lut) {
+            uint8_t *lut = rp->comp_lut + 256 * n;
+            uint8_t zmax = (1 << depth) - 1;
+            uint8_t cmax = (1 << bits) - 1;
+            for (int v = 0; v < 256; v++) {
+                if (rp->pack) {
+                    lut[v] = (v * cmax + zmax / 2) / zmax;
+                } else {
+                    lut[v] = (v & cmax) * zmax / cmax;
+                }
+            }
+        }
+        bitpos += bits;
+    }
+
+    rp->comp_size = (bitpos + 7) / 8;
+    assert(rp->comp_size == 1 || rp->comp_size == 2);
+
+    if (fmt->be) {
+        assert(rp->comp_size == 2);
+        rp->endian_size = 2;
+    }
+}
+
+static void unpack_pal(struct mp_repack *rp,
+                       struct mp_image *a, int a_x, int a_y,
+                       struct mp_image *b, int b_x, int b_y, int w)
+{
+    uint8_t *src = mp_image_pixel_ptr(a, 0, a_x, a_y);
+    uint32_t *pal = (void *)a->planes[1];
+
+    uint8_t *dst[4] = {0};
+    for (int p = 0; p < b->num_planes; p++)
+        dst[p] = mp_image_pixel_ptr(b, p, b_x, b_y);
+
+    for (int x = 0; x < w; x++) {
+        uint32_t c = pal[src[x]];
+        dst[0][x] = (c >>  8) & 0xFF; // G
+        dst[1][x] = (c >>  0) & 0xFF; // B
+        dst[2][x] = (c >> 16) & 0xFF; // R
+        dst[3][x] = (c >> 24) & 0xFF; // A
+    }
+}
+
+static void bitmap_repack(struct mp_repack *rp,
+                          struct mp_image *a, int a_x, int a_y,
+                          struct mp_image *b, int b_x, int b_y, int w)
+{
+    uint8_t *pa = mp_image_pixel_ptr(a, 0, a_x, a_y);
+    uint8_t *pb = mp_image_pixel_ptr(b, 0, b_x, b_y);
+
+    if (rp->pack) {
+        for (unsigned x = 0; x < w; x += 8) {
+            uint8_t d = 0;
+            int max_b = MPMIN(8, w - x);
+            for (int bp = 0; bp < max_b; bp++)
+                d |= (rp->comp_lut[pb[x + bp]]) << (7 - bp);
+            pa[x / 8] = d;
+        }
+    } else {
+        for (unsigned x = 0; x < w; x += 8) {
+            uint8_t d = pa[x / 8];
+            int max_b = MPMIN(8, w - x);
+            for (int bp = 0; bp < max_b; bp++)
+                pb[x + bp] = rp->comp_lut[d & (1 << (7 - bp))];
+        }
+    }
+}
+
+static void setup_misc_packer(struct mp_repack *rp)
+{
+    // Although it's in regular_repackers[], the generic mpv imgfmt metadata
+    // can't handle it yet.
+    if (rp->imgfmt_a == IMGFMT_RGB30) {
+        int planar_fmt = find_gbrp_format(10, 3);
+        if (!planar_fmt)
+            return;
+        rp->imgfmt_b = planar_fmt;
+        rp->repack = packed_repack;
+        rp->packed_repack_scanline = rp->pack ? pa_ccc10z2 : un_ccc10x2;
+        static int c_order[] = {3, 2, 1};
+        for (int n = 0; n < 3; n++)
+            rp->components[n] = c_order[n] - 1;
+    } else if (rp->imgfmt_a == IMGFMT_PAL8 && !rp->pack) {
+        int grap_fmt = find_gbrp_format(8, 4);
+        if (!grap_fmt)
+            return;
+        rp->imgfmt_b = grap_fmt;
+        rp->repack = unpack_pal;
+    } else {
+        enum AVPixelFormat avfmt = imgfmt2pixfmt(rp->imgfmt_a);
+        if (avfmt == AV_PIX_FMT_MONOWHITE || avfmt == AV_PIX_FMT_MONOBLACK) {
+            rp->comp_lut = talloc_array(rp, uint8_t, 256);
+            rp->imgfmt_b = IMGFMT_Y1;
+            int max = 1;
+            if (rp->flags & REPACK_CREATE_EXPAND_8BIT) {
+                rp->imgfmt_b = IMGFMT_Y8;
+                max = 255;
+            }
+            bool inv = avfmt == AV_PIX_FMT_MONOWHITE;
+            for (int n = 0; n < 256; n++) {
+                rp->comp_lut[n] = rp->pack ? (inv ^ (n >= (max + 1) / 2))
+                                           : ((inv ^ !!n) ? max : 0);
+            }
+            rp->repack = bitmap_repack;
+            return;
+        }
+    }
+}
+
+struct fringe_yuv422_repacker {
+    // To avoid making a mess of IMGFMT_*, we use av formats directly.
+    enum AVPixelFormat avfmt;
+    // In bits (depth/8 rounded up gives byte size)
+    int8_t depth;
+    // Word index of each sample: {y0, y1, cb, cr}
+    uint8_t comp[4];
+    bool be;
+};
+
+static const struct fringe_yuv422_repacker fringe_yuv422_repackers[] = {
+    {AV_PIX_FMT_YUYV422,  8, {0, 2, 1, 3}},
+    {AV_PIX_FMT_UYVY422,  8, {1, 3, 0, 2}},
+    {AV_PIX_FMT_YVYU422,  8, {0, 2, 3, 1}},
+#ifdef AV_PIX_FMT_Y210
+    {AV_PIX_FMT_Y210LE,  10, {0, 2, 1, 3}},
+    {AV_PIX_FMT_Y210BE,  10, {0, 2, 1, 3}, .be = true},
+#endif
+};
+
+#define PA_P422(name, comp_t)                                               \
+    static void name(void *dst, void *src[], int w, uint8_t *c) {           \
+        for (int x = 0; x < w; x += 2) {                                    \
+            ((comp_t *)dst)[x * 2 + c[0]] = ((comp_t *)src[0])[x + 0];      \
+            ((comp_t *)dst)[x * 2 + c[1]] = ((comp_t *)src[0])[x + 1];      \
+            ((comp_t *)dst)[x * 2 + c[2]] = ((comp_t *)src[1])[x >> 1];     \
+            ((comp_t *)dst)[x * 2 + c[3]] = ((comp_t *)src[2])[x >> 1];     \
+        }                                                                   \
+    }
+
+
+#define UN_P422(name, comp_t)                                               \
+    static void name(void *src, void *dst[], int w, uint8_t *c) {           \
+        for (int x = 0; x < w; x += 2) {                                    \
+            ((comp_t *)dst[0])[x + 0]  = ((comp_t *)src)[x * 2 + c[0]];     \
+            ((comp_t *)dst[0])[x + 1]  = ((comp_t *)src)[x * 2 + c[1]];     \
+            ((comp_t *)dst[1])[x >> 1] = ((comp_t *)src)[x * 2 + c[2]];     \
+            ((comp_t *)dst[2])[x >> 1] = ((comp_t *)src)[x * 2 + c[3]];     \
+        }                                                                   \
+    }
+
+PA_P422(pa_p422_8,  uint8_t)
+PA_P422(pa_p422_16, uint16_t)
+UN_P422(un_p422_8,  uint8_t)
+UN_P422(un_p422_16, uint16_t)
+
+static void fringe_yuv422_repack(struct mp_repack *rp,
+                                 struct mp_image *a, int a_x, int a_y,
+                                 struct mp_image *b, int b_x, int b_y, int w)
+{
+    void *pa = mp_image_pixel_ptr(a, 0, a_x, a_y);
+
+    void *pb[4] = {0};
+    for (int p = 0; p < b->num_planes; p++)
+        pb[p] = mp_image_pixel_ptr(b, p, b_x, b_y);
+
+    assert(rp->comp_size == 1 || rp->comp_size == 2);
+
+    void (*repack)(void *a, void *b[], int w, uint8_t *c) = NULL;
+    if (rp->pack) {
+        repack = rp->comp_size == 1 ? pa_p422_8 : pa_p422_16;
+    } else {
+        repack = rp->comp_size == 1 ? un_p422_8 : un_p422_16;
+    }
+    repack(pa, pb, w, rp->comp_map);
+}
+
+static void setup_fringe_yuv422_packer(struct mp_repack *rp)
+{
+    enum AVPixelFormat avfmt = imgfmt2pixfmt(rp->imgfmt_a);
+
+    const struct fringe_yuv422_repacker *fmt = NULL;
+    for (int n = 0; n < MP_ARRAY_SIZE(fringe_yuv422_repackers); n++) {
+        if (fringe_yuv422_repackers[n].avfmt == avfmt) {
+            fmt = &fringe_yuv422_repackers[n];
+            break;
+        }
+    }
+
+    if (!fmt)
+        return;
+
+    rp->comp_size = (fmt->depth + 7) / 8;
+    assert(rp->comp_size == 1 || rp->comp_size == 2);
+
+    struct mp_regular_imgfmt yuvfmt = {
+        .component_type = MP_COMPONENT_TYPE_UINT,
+        // NB: same problem with P010 and not clearing padding.
+        .component_size = rp->comp_size,
+        .num_planes = 3,
+        .planes = { {1, {1}}, {1, {2}}, {1, {3}} },
+        .chroma_xs = 1,
+        .chroma_ys = 0,
+    };
+    rp->imgfmt_b = mp_find_regular_imgfmt(&yuvfmt);
+    rp->repack = fringe_yuv422_repack;
+    rp->comp_map = (uint8_t *)fmt->comp;
+
+    if (fmt->be) {
+        assert(rp->comp_size == 2);
+        rp->endian_size = 2;
+    }
+}
+
+static void repack_nv(struct mp_repack *rp,
+                      struct mp_image *a, int a_x, int a_y,
+                      struct mp_image *b, int b_x, int b_y, int w)
+{
+    int xs = a->fmt.chroma_xs;
+
+    uint32_t *pa = mp_image_pixel_ptr(a, 1, a_x, a_y);
+
+    void *pb[2];
+    for (int p = 0; p < 2; p++) {
+        int s = rp->components[p];
+        pb[p] = mp_image_pixel_ptr(b, s, b_x, b_y);
+    }
+
+    rp->packed_repack_scanline(pa, pb, (w + (1 << xs) - 1) >> xs);
+}
+
+static void setup_nv_packer(struct mp_repack *rp)
+{
+    struct mp_regular_imgfmt desc;
+    if (!mp_get_regular_imgfmt(&desc, rp->imgfmt_a))
+        return;
+
+    // Check for NV.
+    if (desc.num_planes != 2)
+        return;
+    if (desc.planes[0].num_components != 1 || desc.planes[0].components[0] != 1)
+        return;
+    if (desc.planes[1].num_components != 2)
+        return;
+    int cr0 = desc.planes[1].components[0];
+    int cr1 = desc.planes[1].components[1];
+    if (cr0 > cr1)
+        MPSWAP(int, cr0, cr1);
+    if (cr0 != 2 || cr1 != 3)
+        return;
+
+    // Construct equivalent planar format.
+    struct mp_regular_imgfmt desc2 = desc;
+    desc2.num_planes = 3;
+    desc2.planes[1].num_components = 1;
+    desc2.planes[1].components[0] = 2;
+    desc2.planes[2].num_components = 1;
+    desc2.planes[2].components[0] = 3;
+    // For P010. Strangely this concept exists only for the NV format.
+    if (desc2.component_pad > 0)
+        desc2.component_pad = 0;
+
+    int planar_fmt = mp_find_regular_imgfmt(&desc2);
+    if (!planar_fmt)
+        return;
+
+    for (int i = 0; i < MP_ARRAY_SIZE(regular_repackers); i++) {
+        const struct regular_repacker *pa = &regular_repackers[i];
+
+        void (*repack_cb)(void *pa, void *pb[], int w) =
+            rp->pack ? pa->pa_scanline : pa->un_scanline;
+
+        if (pa->packed_width != desc.component_size * 2 * 8 ||
+            pa->component_width != desc.component_size * 8 ||
+            pa->num_components != 2 ||
+            pa->prepadding != 0 ||
+            !repack_cb)
+            continue;
+
+        rp->repack = repack_nv;
+        rp->passthrough_y = true;
+        rp->packed_repack_scanline = repack_cb;
+        rp->imgfmt_b = planar_fmt;
+        rp->components[0] = desc.planes[1].components[0] - 1;
+        rp->components[1] = desc.planes[1].components[1] - 1;
+        return;
+    }
+}
+
+void repack_line(struct mp_repack *rp, int dst_x, int dst_y,
+                 int src_x, int src_y, int w)
+{
+    assert(rp->configured);
+
+    struct repack_step *first = &rp->steps[0];
+    struct repack_step *last = &rp->steps[rp->num_steps - 1];
+
+    assert(dst_x >= 0 && dst_y >= 0 && src_x >= 0 && src_y >= 0 && w >= 0);
+    assert(dst_x + w <= MP_ALIGN_UP(last->buf[1]->w, last->fmt[1].align_x));
+    assert(src_x + w <= MP_ALIGN_UP(first->buf[1]->w, first->fmt[0].align_x));
+    assert(dst_y < last->buf[1]->h);
+    assert(src_y < first->buf[0]->h);
+    assert(!(dst_x & (last->fmt[1].align_x - 1)));
+    assert(!(src_x & (first->fmt[0].align_x - 1)));
+    assert(!(w & ((1 << first->fmt[0].chroma_xs) - 1)));
+    assert(!(dst_y & (last->fmt[1].align_y - 1)));
+    assert(!(src_y & (first->fmt[0].align_y - 1)));
+
+    for (int n = 0; n < rp->num_steps; n++) {
+        struct repack_step *rs = &rp->steps[n];
+
+        // When writing to temporary buffers, always write to the start (maybe
+        // helps with locality).
+        int sx = rs->user_buf[0] ? src_x : 0;
+        int sy = rs->user_buf[0] ? src_y : 0;
+        int dx = rs->user_buf[1] ? dst_x : 0;
+        int dy = rs->user_buf[1] ? dst_y : 0;
+
+        struct mp_image *buf_a = rs->buf[rp->pack];
+        struct mp_image *buf_b = rs->buf[!rp->pack];
+        int a_x = rp->pack ? dx : sx;
+        int a_y = rp->pack ? dy : sy;
+        int b_x = rp->pack ? sx : dx;
+        int b_y = rp->pack ? sy : dy;
+
+        switch (rs->type) {
+        case REPACK_STEP_REPACK: {
+            if (rp->repack)
+                rp->repack(rp, buf_a, a_x, a_y, buf_b, b_x, b_y, w);
+
+            for (int p = 0; p < rs->fmt[0].num_planes; p++) {
+                if (rp->copy_buf[p])
+                    copy_plane(rs->buf[1], dx, dy, rs->buf[0], sx, sy, w, p);
+            }
+            break;
+        }
+        case REPACK_STEP_ENDIAN:
+            swap_endian(rs->buf[1], dx, dy, rs->buf[0], sx, sy, w,
+                        rp->endian_size);