nvdec: Adding Vp8 codec support (#2707)

* first try

* second try

* working update

* Final impl

* Fixes nits

* Fix everything

* remove leftover

* Update FFmpegContext.cs

* Update Surface.cs

* Addresses gdkchan feedback

* bool not byte

* Addresses gdkchan feedback

1 files changed, 53 insertions, 0 deletions

diff --git a/Ryujinx.Graphics.Nvdec.FFmpeg/Vp8/Decoder.cs b/Ryujinx.Graphics.Nvdec.FFmpeg/Vp8/Decoder.cs
new file mode 100644
index 00000000..f12de287
--- /dev/null
+++ b/Ryujinx.Graphics.Nvdec.FFmpeg/Vp8/Decoder.cs
@@ -0,0 +1,53 @@
+using FFmpeg.AutoGen;
+using Ryujinx.Graphics.Video;
+using System;
+
+namespace Ryujinx.Graphics.Nvdec.FFmpeg.Vp8
+{
+    public sealed class Decoder : IDecoder
+    {
+        public bool IsHardwareAccelerated => false;
+
+        private readonly FFmpegContext _context = new FFmpegContext(AVCodecID.AV_CODEC_ID_VP8);
+
+        public ISurface CreateSurface(int width, int height)
+        {
+            return new Surface(width, height);
+        }
+
+        public bool Decode(ref Vp8PictureInfo pictureInfo, ISurface output, ReadOnlySpan<byte> bitstream)
+        {
+            Surface outSurf = (Surface)output;
+
+            int uncompHeaderSize = pictureInfo.KeyFrame ? 10 : 3;
+
+            byte[] frame = new byte[bitstream.Length + uncompHeaderSize];
+
+            uint firstPartSizeShifted = pictureInfo.FirstPartSize << 5;
+
+            frame[0] = (byte)(pictureInfo.KeyFrame ? 0 : 1);
+            frame[0] |= (byte)((pictureInfo.Version & 7) << 1);
+            frame[0] |= 1 << 4;
+            frame[0] |= (byte)firstPartSizeShifted;
+            frame[1] |= (byte)(firstPartSizeShifted >> 8);
+            frame[2] |= (byte)(firstPartSizeShifted >> 16);
+
+            if (pictureInfo.KeyFrame)
+            {
+                frame[3] = 0x9d;
+                frame[4] = 0x01;
+                frame[5] = 0x2a;
+                frame[6] = (byte)pictureInfo.FrameWidth;
+                frame[7] = (byte)((pictureInfo.FrameWidth >> 8) & 0x3F);
+                frame[8] = (byte)pictureInfo.FrameHeight;
+                frame[9] = (byte)((pictureInfo.FrameHeight >> 8) & 0x3F);
+            }
+
+            bitstream.CopyTo(new Span<byte>(frame).Slice(uncompHeaderSize));
+
+            return _context.DecodeFrame(outSurf, frame) == 0;
+        }
+
+        public void Dispose() => _context.Dispose();
+    }
+}
\ No newline at end of file