Fix Black Fallback Frame For Failed Readbacks

Util/FrameReader.cs

@@ -154,14 +154,11 @@ namespace ADOFAIRenderer.Util
                 }
                 Melon<RenderMod>.Logger.Warning($"[OOM Prevent] GPU Readback failed for frame {frame}. Queue deadlock prevented by sending a black frame.");
 
-                var byteSize = state.Width * state.Height * 3 / 2;
+                var blackFrame = CreateBlackFrame(state, out var byteSize);
-                var blackFrame = ArrayPool<byte>.Shared.Rent(byteSize);
-                Array.Clear(blackFrame, 0, byteSize);
-                
                 var capFrame = new RenderManager.CapturedFrame
                 {
                     ManagedBuffer = blackFrame, Length = byteSize,
-                    IsColorConverted = true
+                    IsColorConverted = state.IsGPUConversion
                 };
                 PushToQueue(frame, capFrame);
                 RecycleState(state);
@@ -190,6 +187,36 @@ namespace ADOFAIRenderer.Util
             }
         }
 
+        /// <summary>
+        /// Creates a black frame in the same format as the frames of this reader, from ArrayPool&lt;byte&gt;.Shared
+        /// (returned to the pool by the render thread after encoding).
+        ///
+        ///   GPU conversion (NV12 / YUV420P, full range): Width × Height × 3 / 2 bytes.
+        ///     Y plane (Width × Height bytes) = 0, U/V data (the rest) = 128.
+        ///     128 is the zero chroma value of the 8-bit full range: the U/V offset 0.5 of RGB2YUV_BT709_Full
+        ///     in ColorConversion.compute, which the encoder input of this path uses.
+        ///     Both NV12 (interleaved UV) and YUV420P (U plane, then V plane) store all chroma after the Y plane,
+        ///     so the same fill applies to both.
+        ///   No GPU conversion (RGBA input, converted by the encoder): Width × Height × 4 bytes, all 0.
+        /// </summary>
+        private static byte[] CreateBlackFrame(ReadbackRequestState state, out int byteSize)
+        {
+            var lumaSize = state.Width * state.Height;
+            byteSize = state.IsGPUConversion ? lumaSize * 3 / 2 : lumaSize * 4;
+
+            var frame = ArrayPool<byte>.Shared.Rent(byteSize);
+            if (state.IsGPUConversion)
+            {
+                Array.Clear(frame, 0, lumaSize);
+                frame.AsSpan(lumaSize, byteSize - lumaSize).Fill(128);
+            }
+            else
+            {
+                Array.Clear(frame, 0, byteSize);
+            }
+            return frame;
+        }
+
         internal void RecycleState(ReadbackRequestState state)
         {
             lock (_poolLock)