vo_gpu: hwdec_d3d11va: allow zero-copy video decoding

Like the manual says, this is technically undefined behaviour. See:
https://msdn.microsoft.com/en-us/library/windows/desktop/ff476085.aspx

In particular, MSDN says texture arrays created with the BIND_DECODER
flag cannot be used with CreateShaderResourceView, which means they
can't be sampled through SRVs like normal Direct3D textures. However,
some programs (Google Chrome included) do this anyway for performance
and power-usage reasons, and it appears to work with most drivers.

Older AMD drivers had a "bug" with zero-copy decoding, but this appears
to have been fixed. See #3255, #3464 and http://crbug.com/623029.

1 files changed, 106 insertions, 48 deletions

diff --git a/video/out/d3d11/hwdec_d3d11va.c b/video/out/d3d11/hwdec_d3d11va.c
index f179298ac1..7de24dde28 100644
--- a/video/out/d3d11/hwdec_d3d11va.c
+++ b/video/out/d3d11/hwdec_d3d11va.c
@@ -22,21 +22,45 @@
 #include "config.h"
 
 #include "common/common.h"
+#include "options/m_config.h"
 #include "osdep/windows_utils.h"
 #include "video/hwdec.h"
 #include "video/decode/d3d.h"
 #include "video/out/d3d11/ra_d3d11.h"
 #include "video/out/gpu/hwdec.h"
 
+struct d3d11va_opts {
+    int zero_copy;
+};
+
+#define OPT_BASE_STRUCT struct d3d11va_opts
+const struct m_sub_options d3d11va_conf = {
+    .opts = (const struct m_option[]) {
+        OPT_FLAG("d3d11va-zero-copy", zero_copy, 0),
+        {0}
+    },
+    .defaults = &(const struct d3d11va_opts) {
+        .zero_copy = 0,
+    },
+    .size = sizeof(struct d3d11va_opts)
+};
+
 struct priv_owner {
+    struct d3d11va_opts *opts;
+
     struct mp_hwdec_ctx hwctx;
     ID3D11Device *device;
     ID3D11Device1 *device1;
 };
 
 struct priv {
+    // 1-copy path
     ID3D11DeviceContext1 *ctx;
     ID3D11Texture2D *copy_tex;
+
+    // zero-copy path
+    int num_planes;
+    const struct ra_format *fmt[4];
 };
 
 static void uninit(struct ra_hwdec *hw)
@@ -59,6 +83,8 @@ static int init(struct ra_hwdec *hw)
     if (!p->device)
         return -1;
 
+    p->opts = mp_get_config_group(hw->priv, hw->global, &d3d11va_conf);
+
     // D3D11VA requires Direct3D 11.1, so this should always succeed
     hr = ID3D11Device_QueryInterface(p->device, &IID_ID3D11Device1,
                                      (void**)&p->device1);
@@ -109,52 +135,56 @@ static int mapper_init(struct ra_hwdec_mapper *mapper)
     mapper->dst_params.hw_subfmt = 0;
 
     struct ra_imgfmt_desc desc = {0};
-    struct mp_image layout = {0};
 
     if (!ra_get_imgfmt_desc(mapper->ra, mapper->dst_params.imgfmt, &desc))
         return -1;
 
-    mp_image_set_params(&layout, &mapper->dst_params);
-
-    DXGI_FORMAT copy_fmt;
-    switch (mapper->dst_params.imgfmt) {
-    case IMGFMT_NV12: copy_fmt = DXGI_FORMAT_NV12; break;
-    case IMGFMT_P010: copy_fmt = DXGI_FORMAT_P010; break;
-    default: return -1;
-    }
-
-    // We copy decoder images to an intermediate texture. This is slower than
-    // the zero-copy path, but according to MSDN, decoder textures should not
-    // be bound to SRVs, so it is technically correct, and it works around some
-    // driver "bugs" that can happen with the zero-copy path. It also allows
-    // samplers to work correctly when the decoder image includes padding.
-    D3D11_TEXTURE2D_DESC copy_desc = {
-        .Width = mapper->dst_params.w,
-        .Height = mapper->dst_params.h,
-        .MipLevels = 1,
-        .ArraySize = 1,
-        .SampleDesc.Count = 1,
-        .Format = copy_fmt,
-        .BindFlags = D3D11_BIND_SHADER_RESOURCE,
-    };
-    hr = ID3D11Device_CreateTexture2D(o->device, &copy_desc, NULL, &p->copy_tex);
-    if (FAILED(hr)) {
-        MP_FATAL(mapper, "Could not create shader resource texture\n");
-        return -1;
-    }
+    if (o->opts->zero_copy) {
+        // In the zero-copy path, we create the ra_tex objects in the map
+        // operation, so we just need to store the format of each plane
+        p->num_planes = desc.num_planes;
+        for (int i = 0; i < desc.num_planes; i++)
+            p->fmt[i] = desc.planes[i];
+    } else {
+        struct mp_image layout = {0};
+        mp_image_set_params(&layout, &mapper->dst_params);
+
+        DXGI_FORMAT copy_fmt;
+        switch (mapper->dst_params.imgfmt) {
+        case IMGFMT_NV12: copy_fmt = DXGI_FORMAT_NV12; break;
+        case IMGFMT_P010: copy_fmt = DXGI_FORMAT_P010; break;
+        default: return -1;
+        }
 
-    for (int i = 0; i < desc.num_planes; i++) {
-        mapper->tex[i] = ra_d3d11_wrap_tex_video(mapper->ra, p->copy_tex,
-                                                 mp_image_plane_w(&layout, i),
-                                                 mp_image_plane_h(&layout, i),
-                                                 desc.planes[i]);
-        if (!mapper->tex[i]) {
-            MP_FATAL(mapper, "Could not create RA texture view\n");
+        D3D11_TEXTURE2D_DESC copy_desc = {
+            .Width = mapper->dst_params.w,
+            .Height = mapper->dst_params.h,
+            .MipLevels = 1,
+            .ArraySize = 1,
+            .SampleDesc.Count = 1,
+            .Format = copy_fmt,
+            .BindFlags = D3D11_BIND_SHADER_RESOURCE,
+        };
+        hr = ID3D11Device_CreateTexture2D(o->device, &copy_desc, NULL,
+                                          &p->copy_tex);
+        if (FAILED(hr)) {
+            MP_FATAL(mapper, "Could not create shader resource texture\n");
             return -1;
         }
-    }
 
-    ID3D11Device1_GetImmediateContext1(o->device1, &p->ctx);
+        for (int i = 0; i < desc.num_planes; i++) {
+            mapper->tex[i] = ra_d3d11_wrap_tex_video(mapper->ra, p->copy_tex,
+                mp_image_plane_w(&layout, i), mp_image_plane_h(&layout, i), 0,
+                desc.planes[i]);
+            if (!mapper->tex[i]) {
+                MP_FATAL(mapper, "Could not create RA texture view\n");
+                return -1;
+            }
+        }
+
+        // A ref to the immediate context is needed for CopySubresourceRegion
+        ID3D11Device1_GetImmediateContext1(o->device1, &p->ctx);
+    }
 
     return 0;
 }
@@ -165,20 +195,47 @@ static int mapper_map(struct ra_hwdec_mapper *mapper)
     ID3D11Texture2D *tex = (void *)mapper->src->planes[0];
     int subresource = (intptr_t)mapper->src->planes[1];
 
-    ID3D11DeviceContext1_CopySubresourceRegion1(p->ctx,
-        (ID3D11Resource *)p->copy_tex, 0, 0, 0, 0,
-        (ID3D11Resource *)tex, subresource, (&(D3D11_BOX) {
-            .left = 0,
-            .top = 0,
-            .front = 0,
-            .right = mapper->dst_params.w,
-            .bottom = mapper->dst_params.h,
-            .back = 1,
-        }), D3D11_COPY_DISCARD);
+    if (p->copy_tex) {
+        ID3D11DeviceContext1_CopySubresourceRegion1(p->ctx,
+            (ID3D11Resource *)p->copy_tex, 0, 0, 0, 0,
+            (ID3D11Resource *)tex, subresource, (&(D3D11_BOX) {
+                .left = 0,
+                .top = 0,
+                .front = 0,
+                .right = mapper->dst_params.w,
+                .bottom = mapper->dst_params.h,
+                .back = 1,
+            }), D3D11_COPY_DISCARD);
+    } else {
+        D3D11_TEXTURE2D_DESC desc2d;
+        ID3D11Texture2D_GetDesc(tex, &desc2d);
+
+        for (int i = 0; i < p->num_planes; i++) {
+            // The video decode texture may include padding, so the size of the
+            // ra_tex needs to be determined by the actual size of the Tex2D
+            bool chroma = i >= 1;
+            int w = desc2d.Width / (chroma ? 2 : 1);
+            int h = desc2d.Height / (chroma ? 2 : 1);
+
+            mapper->tex[i] = ra_d3d11_wrap_tex_video(mapper->ra, tex,
+                w, h, subresource, p->fmt[i]);
+            if (!mapper->tex[i])
+                return -1;
+        }
+    }
 
     return 0;
 }
 
+static void mapper_unmap(struct ra_hwdec_mapper *mapper)
+{
+    struct priv *p = mapper->priv;
+    if (p->copy_tex)
+        return;
+    for (int i = 0; i < 4; i++)
+        ra_tex_free(mapper->ra, &mapper->tex[i]);
+}
+
 const struct ra_hwdec_driver ra_hwdec_d3d11va = {
     .name = "d3d11va",
     .priv_size = sizeof(struct priv_owner),
@@ -191,5 +248,6 @@ const struct ra_hwdec_driver ra_hwdec_d3d11va = {
         .init = mapper_init,
         .uninit = mapper_uninit,
         .map = mapper_map,
+        .unmap = mapper_unmap,
     },
 };