NVDEC implementation using FFmpeg (#443)

* Initial nvdec implementation using FFmpeg

* Fix swapped channels on the video decoder and the G8R8 texture format

* Fix texture samplers not being set properly (regression)

* Rebased

* Remove unused code introduced on the rebase

* Add support for RGBA8 output format on the video image composer

* Correct spacing

* Some fixes for rebase and other tweaks

* Allow size mismatch on frame copy

* Get rid of GetHostAddress calls on VDec

2 files changed, 35 insertions, 2 deletions

diff --git a/Ryujinx.Graphics/Memory/NvGpuBufferType.cs b/Ryujinx.Graphics/Memory/NvGpuBufferType.cs
new file mode 100644
index 00000000..6f0d2571
--- /dev/null
+++ b/Ryujinx.Graphics/Memory/NvGpuBufferType.cs
@@ -0,0 +1,11 @@
+namespace Ryujinx.Graphics.Memory
+{
+    public enum NvGpuBufferType
+    {
+        Index,
+        Vertex,
+        Texture,
+        ConstBuffer,
+        Count
+    }
+}
\ No newline at end of file
diff --git a/Ryujinx.Graphics/Memory/NvGpuVmm.cs b/Ryujinx.Graphics/Memory/NvGpuVmm.cs
index ccb21950..cfd1aaeb 100644
--- a/Ryujinx.Graphics/Memory/NvGpuVmm.cs
+++ b/Ryujinx.Graphics/Memory/NvGpuVmm.cs
@@ -72,6 +72,28 @@ namespace Ryujinx.Graphics.Memory
             }
         }
 
+        public long MapLow(long PA, long Size)
+        {
+            lock (PageTable)
+            {
+                long VA = GetFreePosition(Size, 1, PageSize);
+
+                if (VA != -1 && (ulong)VA <= uint.MaxValue && (ulong)(VA + Size) <= uint.MaxValue)
+                {
+                    for (long Offset = 0; Offset < Size; Offset += PageSize)
+                    {
+                        SetPte(VA + Offset, PA + Offset);
+                    }
+                }
+                else
+                {
+                    VA = -1;
+                }
+
+                return VA;
+            }
+        }
+
         public long ReserveFixed(long VA, long Size)
         {
             lock (PageTable)
@@ -122,11 +144,11 @@ namespace Ryujinx.Graphics.Memory
             }
         }
 
-        private long GetFreePosition(long Size, long Align = 1)
+        private long GetFreePosition(long Size, long Align = 1, long Start = 1L << 32)
         {
             //Note: Address 0 is not considered valid by the driver,
             //when 0 is returned it's considered a mapping error.
-            long Position = PageSize;
+            long Position = Start;
             long FreeSize = 0;
 
             if (Align < 1)