vo_opengl: hwdec_cuda: directly map GL textures and skip using PBOs

The documentation around this stuff is poor, but I found an nvidia
sample that demonstrates how to use the interop API most efficiently.

(https://github.com/nvpro-samples/gl_cuda_interop_pingpong_st)

Key lessons are:
1) you can register the texture itself and have cuda write to it,
   thereby skipping an additional copy through the PBO.
2) You don't have to be mapped when you do the copy - once you get a
   mapped pointer, it remains valid. Magic!

This lets us throw out the PBOs as well as much of the explicit
alignment and stride handling.

CPU usage is slightly (~3%) lower for 4K content in one test case,
so it makes a detectable difference, and presumably saves memory.

1 files changed, 20 insertions, 65 deletions

diff --git a/video/out/opengl/hwdec_cuda.c b/video/out/opengl/hwdec_cuda.c
index c42d736bf2..c58b00e71f 100644
--- a/video/out/opengl/hwdec_cuda.c
+++ b/video/out/opengl/hwdec_cuda.c
@@ -40,8 +40,8 @@ struct priv {
     struct mp_hwdec_ctx hwctx;
     struct mp_image layout;
     GLuint gl_textures[2];
-    GLuint gl_pbos[2];
     CUgraphicsResource cu_res[2];
+    CUarray cu_array[2];
     bool mapped;
 
     CUcontext cuda_ctx;
@@ -197,24 +197,26 @@ static int reinit(struct gl_hwdec *hw, struct mp_image_params *params)
                        mp_image_plane_w(&p->layout, n),
                        mp_image_plane_h(&p->layout, n),
                        0, n == 0 ? GL_RED : GL_RG, GL_UNSIGNED_BYTE, NULL);
-    }
-    gl->BindTexture(GL_TEXTURE_2D, 0);
+        gl->BindTexture(GL_TEXTURE_2D, 0);
 
-    gl->GenBuffers(2, p->gl_pbos);
-    for (int n = 0; n < 2; n++) {
-        gl->BindBuffer(GL_PIXEL_UNPACK_BUFFER, p->gl_pbos[n]);
-        // Chroma plane is two bytes per pixel
-        gl->BufferData(GL_PIXEL_UNPACK_BUFFER,
-                       mp_image_plane_w(&p->layout, n) *
-                       mp_image_plane_h(&p->layout, n) * (n + 1),
-                       NULL, GL_STREAM_DRAW);
-        gl->BindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);
-        ret = CHECK_CU(cuGraphicsGLRegisterBuffer(&p->cu_res[n],
-                                                  p->gl_pbos[n],
-                                                  CU_GRAPHICS_MAP_RESOURCE_FLAGS_WRITE_DISCARD));
+        ret = CHECK_CU(cuGraphicsGLRegisterImage(&p->cu_res[n], p->gl_textures[n],
+                                                 GL_TEXTURE_2D,
+                                                 CU_GRAPHICS_REGISTER_FLAGS_WRITE_DISCARD));
+        if (ret < 0)
+            goto error;
+
+        ret = CHECK_CU(cuGraphicsMapResources(1, &p->cu_res[n], 0));
+        if (ret < 0)
+            goto error;
+
+        ret = CHECK_CU(cuGraphicsSubResourceGetMappedArray(&p->cu_array[n], p->cu_res[n],
+                                                           0, 0));
         if (ret < 0)
             goto error;
 
+        ret = CHECK_CU(cuGraphicsUnmapResources(1, &p->cu_res[n], 0));
+        if (ret < 0)
+            goto error;
     }
 
  error:
@@ -239,28 +241,15 @@ static void destroy(struct gl_hwdec *hw)
     }
     CHECK_CU(cuCtxPopCurrent(&dummy));
 
-    gl->DeleteBuffers(2, p->gl_pbos);
     gl->DeleteTextures(2, p->gl_textures);
 
     hwdec_devices_remove(hw->devs, &p->hwctx);
 }
 
-static int get_alignment(int stride)
-{
-    if (stride % 8 == 0)
-        return 8;
-    if (stride % 4 == 0)
-        return 4;
-    if (stride % 2 == 0)
-        return 2;
-    return 1;
-}
-
 static int map_frame(struct gl_hwdec *hw, struct mp_image *hw_image,
                      struct gl_hwdec_frame *out_frame)
 {
     struct priv *p = hw->priv;
-    GL *gl = hw->gl;
     CUcontext dummy;
     int ret = 0, eret = 0;
 
@@ -270,29 +259,16 @@ static int map_frame(struct gl_hwdec *hw, struct mp_image *hw_image,
 
     *out_frame = (struct gl_hwdec_frame) { 0, };
 
-    ret = CHECK_CU(cuGraphicsMapResources(2, p->cu_res, NULL));
-    if (ret < 0)
-        goto error;
     for (int n = 0; n < 2; n++) {
-        CUdeviceptr cuda_data;
-        size_t cuda_size;
-
-        ret = CHECK_CU(cuGraphicsResourceGetMappedPointer(&cuda_data,
-                                                          &cuda_size,
-                                                          p->cu_res[n]));
-        if (ret < 0)
-            goto error;
-
-        // dstPitch and widthInBytes must account for the chroma plane
+        // widthInBytes must account for the chroma plane
         // elements being two bytes wide.
         CUDA_MEMCPY2D cpy = {
             .srcMemoryType = CU_MEMORYTYPE_DEVICE,
-            .dstMemoryType = CU_MEMORYTYPE_DEVICE,
+            .dstMemoryType = CU_MEMORYTYPE_ARRAY,
             .srcDevice     = (CUdeviceptr)hw_image->planes[n],
-            .dstDevice     = cuda_data,
             .srcPitch      = hw_image->stride[n],
-            .dstPitch      = mp_image_plane_w(&p->layout, n) * (n + 1),
             .srcY          = 0,
+            .dstArray      = p->cu_array[n],
             .WidthInBytes  = mp_image_plane_w(&p->layout, n) * (n + 1),
             .Height        = mp_image_plane_h(&p->layout, n),
         };
@@ -300,27 +276,6 @@ static int map_frame(struct gl_hwdec *hw, struct mp_image *hw_image,
         if (ret < 0)
             goto error;
 
-    }
-    ret = CHECK_CU(cuGraphicsUnmapResources(2, p->cu_res, NULL));
-    if (ret < 0)
-        goto error;
-
-    for (int n = 0; n < 2; n++) {
-        gl->BindBuffer(GL_PIXEL_UNPACK_BUFFER, p->gl_pbos[n]);
-        gl->BindTexture(GL_TEXTURE_2D, p->gl_textures[n]);
-        gl->PixelStorei(GL_UNPACK_ALIGNMENT,
-                        get_alignment(mp_image_plane_w(&p->layout, n)));
-
-        gl->TexSubImage2D(GL_TEXTURE_2D, 0,
-                          0, 0,
-                          mp_image_plane_w(&p->layout, n),
-                          mp_image_plane_h(&p->layout, n),
-                          n == 0 ? GL_RED : GL_RG, GL_UNSIGNED_BYTE, NULL);
-
-        gl->PixelStorei(GL_UNPACK_ALIGNMENT, 4);
-        gl->BindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);
-        gl->BindTexture(GL_TEXTURE_2D, 0);
-
         out_frame->planes[n] = (struct gl_hwdec_plane){
             .gl_texture = p->gl_textures[n],
             .gl_target = GL_TEXTURE_2D,