vo_gpu: d3d11: initial implementation

This is a new RA/vo_gpu backend that uses Direct3D 11. The GLSL
generated by vo_gpu is cross-compiled to HLSL with SPIRV-Cross.

What works:

- All of mpv's internal shaders should work, including compute shaders.

- Some external shaders have been tested and work, including RAVU and
  adaptive-sharpen.

- Non-dumb mode works, even on very old hardware. Most features work at
  feature level 9_3 and all features work at feature level 10_0. Some
  features also work at feature level 9_1 and 9_2, but without high-bit-
  depth FBOs, it's not very useful. (Hardware this old is probably not
  fast enough for advanced features anyway.)

  Note: This is more compatible than ANGLE, which requires 9_3 to work
  at all (GLES 2.0,) and 10_1 for non-dumb-mode (GLES 3.0.)

- Hardware decoding with D3D11VA, including decoding of 10-bit formats
  without truncation to 8-bit.

What doesn't work / can be improved:

- PBO upload and direct rendering does not work yet. Direct rendering
  requires persistent-mapped PBOs because the decoder needs to be able
  to read data from images that have already been decoded and uploaded.
  Unfortunately, it seems like persistent-mapped PBOs are fundamentally
  incompatible with D3D11, which requires all resources to use driver-
  managed memory and requires memory to be unmapped (and hence pointers
  to be invalidated) when a resource is used in a draw or copy
  operation.

  However it might be possible to use D3D11's limited multithreading
  capabilities to emulate some features of PBOs, like asynchronous
  texture uploading.

- The blit() and clear() operations don't have equivalents in the D3D11
  API that handle all cases, so in most cases, they have to be emulated
  with a shader. This is currently done inside ra_d3d11, but ideally it
  would be done in generic code, so it can take advantage of mpv's
  shader generation utilities.

- SPIRV-Cross is used through a NIH C-compatible wrapper library, since
  it does not expose a C interface itself.

  The library is available here: https://github.com/rossy/crossc

- The D3D11 context could be made to support more modern DXGI features
  in future. For example, it should be possible to add support for
  high-bit-depth and HDR output with DXGI 1.5/1.6.

1 files changed, 34 insertions, 0 deletions

diff --git a/video/out/d3d11/ra_d3d11.h b/video/out/d3d11/ra_d3d11.h
new file mode 100644
index 0000000000..eeadc7994e
--- /dev/null
+++ b/video/out/d3d11/ra_d3d11.h
@@ -0,0 +1,34 @@
+#pragma once
+
+#include <stdbool.h>
+#include <windows.h>
+#include <d3d11.h>
+#include <dxgi1_2.h>
+
+#include "video/out/gpu/ra.h"
+#include "video/out/gpu/spirv.h"
+
+// Create an RA instance from a D3D11 device. This takes a reference to the
+// device, which is released when the RA instance is destroyed.
+struct ra *ra_d3d11_create(ID3D11Device *device, struct mp_log *log,
+                           struct spirv_compiler *spirv);
+
+// Flush the immediate context of the wrapped D3D11 device
+void ra_d3d11_flush(struct ra *ra);
+
+// Create an RA texture from a D3D11 resource. This takes a reference to the
+// texture, which is released when the RA texture is destroyed.
+struct ra_tex *ra_d3d11_wrap_tex(struct ra *ra, ID3D11Resource *res);
+
+// As above, but for a D3D11VA video resource. The fmt parameter selects which
+// plane of a planar format will be mapped when the RA texture is used.
+struct ra_tex *ra_d3d11_wrap_tex_video(struct ra *ra, ID3D11Texture2D *res,
+                                       int w, int h,
+                                       const struct ra_format *fmt);
+
+// Get the underlying D3D11 device from an RA instance. The returned device is
+// refcounted and must be released by the caller.
+ID3D11Device *ra_d3d11_get_device(struct ra *ra);
+
+// True if the RA instance was created with ra_d3d11_create()
+bool ra_is_d3d11(struct ra *ra);