vf_gpu: add video filter using vo_gpu's renderer

Probably pretty useless in this form (see: the wall of warnings), but
someone wanted this.

I think this should be useful to perform some automated tests, maybe.

Fixes: #7194

DOCS/man/vf.rst

@@ -710,3 +710,39 @@ Available mpv-only filters are:
         Print computed fingerprints the the terminal (default: no). This is
         mostly for testing and such. Scripts should use ``vf-metadata`` to
         read information from this filter instead.
+
+``gpu=...``
+    Convert video to RGB using the OpenGL renderer normally used with
+    ``--vo=gpu``. This requires that the EGL implementation supports off-screen
+    rendering on the default display. (This is the case with Mesa.)
+
+    Sub-options:
+
+    ``w=<pixels>``, ``h=<pixels>``
+        Size of the output in pixels (default: 0). If not positive, this will
+        use the size of the first filtered input frame.
+
+    .. warning::
+
+        This is highly experimental. Performance is bad, and it will not work
+        everywhere in the first place. Some features are not supported.
+
+    .. warning::
+
+        This does not do OSD rendering. If you see OSD or subtitles, then these
+        have been renderer by the VO backend (or the ``sub`` video filter). This
+        is normally done in software, and potentially questionable quality.
+
+    .. warning::
+
+        If you use this with encoding mode, keep in mind that encoding mode will
+        convert the RGB filter's output back to yuv420p in software, using the
+        configured software scaler. Using ``zimg`` might improve this, but in
+        any case it might go against your goals when using this filter.
+
+    .. warning::
+
+        Do not use this with ``--vo=gpu``. It will apply filtering twice, since
+        most ``--vo=gpu`` options are unconditionally applied to the ``gpu``
+        filter. There is no mechanism in mpv to prevent this.
+

filters/user_filters.c

@@ -85,6 +85,9 @@ const struct mp_user_filter_entry *vf_list[] = {
 #if HAVE_D3D_HWACCEL
     &vf_d3d11vpp,
 #endif
+#if HAVE_EGL_X11
+    &vf_gpu,
+#endif
 };
 
 static bool get_vf_desc(struct m_obj_desc *dst, int index)

filters/user_filters.h

@@ -34,3 +34,4 @@ extern const struct mp_user_filter_entry vf_vdpaupp;
 extern const struct mp_user_filter_entry vf_vavpp;
 extern const struct mp_user_filter_entry vf_d3d11vpp;
 extern const struct mp_user_filter_entry vf_fingerprint;
+extern const struct mp_user_filter_entry vf_gpu;

video/filter/vf_gpu.c

@@ -0,0 +1,364 @@
+/*
+ * 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 "common/common.h"
+#include "filters/filter.h"
+#include "filters/filter_internal.h"
+#include "filters/user_filters.h"
+#include "options/m_config.h"
+#include "options/m_option.h"
+#include "options/options.h"
+#include "video/out/aspect.h"
+#include "video/out/gpu/video.h"
+#include "video/out/opengl/egl_helpers.h"
+#include "video/out/opengl/ra_gl.h"
+
+struct offscreen_ctx {
+    struct mp_log *log;
+    struct ra *ra;
+    void *priv;
+
+    void (*set_context)(struct offscreen_ctx *ctx, bool enable);
+};
+
+struct gl_offscreen_ctx {
+    GL gl;
+    EGLDisplay egl_display;
+    EGLContext egl_context;
+};
+
+static void gl_ctx_destroy(void *p)
+{
+    struct offscreen_ctx *ctx = p;
+    struct gl_offscreen_ctx *gl = ctx->priv;
+
+    ra_free(&ctx->ra);
+
+    if (gl->egl_context)
+        eglDestroyContext(gl->egl_display, gl->egl_context);
+}
+
+static void gl_ctx_set_context(struct offscreen_ctx *ctx, bool enable)
+{
+    struct gl_offscreen_ctx *gl = ctx->priv;
+    EGLContext c = enable ? gl->egl_context : EGL_NO_CONTEXT;
+
+    if (!eglMakeCurrent(gl->egl_display, EGL_NO_SURFACE, EGL_NO_SURFACE, c))
+        MP_ERR(ctx, "Could not make EGL context current.\n");
+}
+
+static struct offscreen_ctx *gl_offscreen_ctx_create(struct mpv_global *global,
+                                                     struct mp_log *log)
+{
+    struct offscreen_ctx *ctx = talloc_zero(NULL, struct offscreen_ctx);
+    struct gl_offscreen_ctx *gl = talloc_zero(ctx, struct gl_offscreen_ctx);
+    talloc_set_destructor(ctx, gl_ctx_destroy);
+    *ctx = (struct offscreen_ctx){
+        .log = log,
+        .priv = gl,
+        .set_context = gl_ctx_set_context,
+    };
+
+    // This appears to work with Mesa. EGL 1.5 doesn't specify what a "default
+    // display" is at all.
+    gl->egl_display = eglGetDisplay(EGL_DEFAULT_DISPLAY);
+    if (!eglInitialize(gl->egl_display, NULL, NULL)) {
+        MP_ERR(ctx, "Could not initialize EGL.\n");
+        goto error;
+    }
+
+    // Unfortunately, mpegl_create_context() is entangled with ra_ctx.
+    // Fortunately, it does not need much, and we can provide a stub.
+    struct ra_ctx ractx = {
+        .log = ctx->log,
+        .global = global,
+    };
+    EGLConfig config;
+    if (!mpegl_create_context(&ractx, gl->egl_display, &gl->egl_context, &config))
+    {
+        MP_ERR(ctx, "Could not create EGL context.\n");
+        goto error;
+    }
+
+    if (!eglMakeCurrent(gl->egl_display, EGL_NO_SURFACE, EGL_NO_SURFACE,
+                        gl->egl_context))
+    {
+        MP_ERR(ctx, "Could not make EGL context current.\n");
+        goto error;
+    }
+
+    mpegl_load_functions(&gl->gl, ctx->log);
+    ctx->ra = ra_create_gl(&gl->gl, ctx->log);
+
+    if (!ctx->ra)
+        goto error;
+
+    gl_ctx_set_context(ctx, false);
+
+    return ctx;
+
+error:
+    talloc_free(ctx);
+    return NULL;
+}
+
+static void offscreen_ctx_set_current(struct offscreen_ctx *ctx, bool enable)
+{
+    if (ctx->set_context)
+        ctx->set_context(ctx, enable);
+}
+
+struct gpu_opts {
+    int w, h;
+};
+
+struct priv {
+    struct gpu_opts *opts;
+    struct m_config_cache *vo_opts_cache;
+    struct mp_vo_opts *vo_opts;
+
+    struct offscreen_ctx *ctx;
+    struct gl_video *renderer;
+    struct ra_tex *target;
+
+    struct mp_image_params img_params;
+    uint64_t next_frame_id;
+};
+
+static struct mp_image *gpu_render_frame(struct mp_filter *f, struct mp_image *in)
+{
+    struct priv *priv = f->priv;
+    bool ok = false;
+    struct mp_image *res = NULL;
+    struct ra *ra = priv->ctx->ra;
+
+    if (priv->opts->w <= 0)
+        priv->opts->w = in->w;
+    if (priv->opts->h <= 0)
+        priv->opts->h = in->h;
+
+    int w = priv->opts->w;
+    int h = priv->opts->h;
+
+    struct vo_frame frame = {
+        .pts = in->pts,
+        .duration = -1,
+        .num_vsyncs = 1,
+        .current = in,
+        .num_frames = 1,
+        .frames = {in},
+        .frame_id = ++(priv->next_frame_id),
+    };
+
+    bool need_reconfig = m_config_cache_update(priv->vo_opts_cache);
+
+    if (!mp_image_params_equal(&priv->img_params, &in->params)) {
+        priv->img_params = in->params;
+        gl_video_config(priv->renderer, &in->params);
+        need_reconfig = true;
+    }
+
+    if (need_reconfig) {
+        struct mp_rect src, dst;
+        struct mp_osd_res osd;
+
+        mp_get_src_dst_rects(f->log, priv->vo_opts, VO_CAP_ROTATE90, &in->params,
+                             w, h, 1, &src, &dst, &osd);
+
+        gl_video_resize(priv->renderer, &src, &dst, &osd);
+    }
+
+    if (!priv->target) {
+        struct ra_tex_params params = {
+            .dimensions = 2,
+            .downloadable = true,
+            .w = w,
+            .h = h,
+            .render_dst = true,
+        };
+
+        params.format = ra_find_unorm_format(ra, 1, 4);
+
+        if (!params.format || !params.format->renderable)
+            goto done;
+
+        priv->target = ra_tex_create(ra, &params);
+        if (!priv->target)
+            goto done;
+    }
+
+    // (it doesn't have access to the OSD though)
+    int flags = RENDER_FRAME_SUBS | RENDER_FRAME_OSD;
+    gl_video_render_frame(priv->renderer, &frame, (struct ra_fbo){priv->target},
+                          flags);
+
+    res = mp_image_alloc(IMGFMT_RGB0, w, h);
+    if (!res)
+        goto done;
+
+    struct ra_tex_download_params download_params = {
+        .tex = priv->target,
+        .dst = res->planes[0],
+        .stride = res->stride[0],
+    };
+    if (!ra->fns->tex_download(ra, &download_params))
+        goto done;
+
+    ok = true;
+done:
+    if (!ok)
+        TA_FREEP(&res);
+    return res;
+}
+
+static void gpu_process(struct mp_filter *f)
+{
+    struct priv *priv = f->priv;
+
+    if (!mp_pin_can_transfer_data(f->ppins[1], f->ppins[0]))
+        return;
+
+    struct mp_frame frame = mp_pin_out_read(f->ppins[0]);
+
+    if (mp_frame_is_signaling(frame)) {
+        mp_pin_in_write(f->ppins[1], frame);
+        return;
+    }
+
+    if (frame.type != MP_FRAME_VIDEO)
+        goto error;
+
+    offscreen_ctx_set_current(priv->ctx, true);
+
+    struct mp_image *mpi = frame.data;
+    struct mp_image *res = gpu_render_frame(f, mpi);
+    if (!res) {
+        MP_ERR(f, "Could not render or retrieve frame.\n");
+        goto error;
+    }
+
+    // It's not clear which parameters to copy.
+    res->pts = mpi->pts;
+    res->dts = mpi->dts;
+    res->nominal_fps = mpi->nominal_fps;
+
+    talloc_free(mpi);
+
+    mp_pin_in_write(f->ppins[1], MAKE_FRAME(MP_FRAME_VIDEO, res));
+    return;
+
+error:
+    mp_frame_unref(&frame);
+    mp_filter_internal_mark_failed(f);
+    offscreen_ctx_set_current(priv->ctx, false);
+}
+
+static void gpu_reset(struct mp_filter *f)
+{
+    struct priv *priv = f->priv;
+
+    offscreen_ctx_set_current(priv->ctx, true);
+    gl_video_reset(priv->renderer);
+    offscreen_ctx_set_current(priv->ctx, false);
+}
+
+static void gpu_destroy(struct mp_filter *f)
+{
+    struct priv *priv = f->priv;
+
+    if (priv->ctx) {
+        offscreen_ctx_set_current(priv->ctx, true);
+
+        gl_video_uninit(priv->renderer);
+        ra_tex_free(priv->ctx->ra, &priv->target);
+
+        offscreen_ctx_set_current(priv->ctx, false);
+    }
+
+    talloc_free(priv->ctx);
+}
+
+static const struct mp_filter_info gpu_filter = {
+    .name = "gpu",
+    .process = gpu_process,
+    .reset = gpu_reset,
+    .destroy = gpu_destroy,
+    .priv_size = sizeof(struct priv),
+};
+
+static struct mp_filter *gpu_create(struct mp_filter *parent, void *options)
+{
+    struct mp_filter *f = mp_filter_create(parent, &gpu_filter);
+    if (!f) {
+        talloc_free(options);
+        return NULL;
+    }
+
+    mp_filter_add_pin(f, MP_PIN_IN, "in");
+    mp_filter_add_pin(f, MP_PIN_OUT, "out");
+
+    struct priv *priv = f->priv;
+    priv->opts = talloc_steal(priv, options);
+    priv->vo_opts_cache = m_config_cache_alloc(f, f->global, &vo_sub_opts);
+    priv->vo_opts = priv->vo_opts_cache->opts;
+
+    priv->ctx = gl_offscreen_ctx_create(f->global, f->log);
+    if (!priv->ctx) {
+        MP_FATAL(f, "Could not create offscreen ra context.\n");
+        goto error;
+    }
+
+    if (!priv->ctx->ra->fns->tex_download) {
+        MP_FATAL(f, "Offscreen ra context does not support image retrieval.\n");
+        goto error;
+    }
+
+    offscreen_ctx_set_current(priv->ctx, true);
+
+    priv->renderer = gl_video_init(priv->ctx->ra, f->log, f->global);
+    assert(priv->renderer); // can't fail (strangely)
+
+    offscreen_ctx_set_current(priv->ctx, false);
+
+    MP_WARN(f, "This is experimental. Keep in mind:\n");
+    MP_WARN(f, " - OSD rendering is done in software.\n");
+    MP_WARN(f, " - Encoding will convert the RGB output to yuv420p in software.\n");
+    MP_WARN(f, " - Using this with --vo=gpu will filter the video twice!\n");
+    MP_WARN(f, "   (And you can't prevent this; they use the same options.)\n");
+    MP_WARN(f, " - Some features are simply not supported.\n");
+
+    return f;
+
+error:
+    talloc_free(f);
+    return NULL;
+}
+
+#define OPT_BASE_STRUCT struct gpu_opts
+const struct mp_user_filter_entry vf_gpu = {
+    .desc = {
+        .description = "vo_gpu as filter",
+        .name = "gpu",
+        .priv_size = sizeof(OPT_BASE_STRUCT),
+        .options = (const struct m_option[]){
+            OPT_INT("w", w, 0),
+            OPT_INT("h", h, 0),
+            {0}
+        },
+    },
+    .create = gpu_create,
+};

wscript_build.py

@@ -415,6 +415,7 @@ def build(ctx):
         ( "video/filter/vf_d3d11vpp.c",          "d3d-hwaccel" ),
         ( "video/filter/vf_fingerprint.c",       "zimg" ),
         ( "video/filter/vf_format.c" ),
+        ( "video/filter/vf_gpu.c",               "egl-helpers && gl && egl15" ),
         ( "video/filter/vf_sub.c" ),
         ( "video/filter/vf_vapoursynth.c",       "vapoursynth" ),
         ( "video/filter/vf_vavpp.c",             "vaapi" ),