AVWriters now implement UsesAudio and UsesVideo so that the frontend can decide how much work it needs to tell the core to do to fulfill the AVWriter's needs (fixes #593)

BizHawk.Client.EmuHawk/AVOut/AVSync.cs

@@ -175,6 +175,9 @@ namespace BizHawk.Client.EmuHawk
 	{
 		protected IVideoWriter w;
 
+		public bool UsesAudio { get { return w.UsesAudio; } }
+		public bool UsesVideo { get { return w.UsesVideo; } }
+
 		public void SetVideoCodecToken(IDisposable token)
 		{
 			w.SetVideoCodecToken(token);

BizHawk.Client.EmuHawk/AVOut/AviWriter.cs

@@ -857,6 +857,9 @@ namespace BizHawk.Client.EmuHawk
 		{
 			return "avi";
 		}
+
+		public bool UsesAudio { get { return parameters.has_audio; } }
+		public bool UsesVideo { get { return true; } }
 	}
 }
 

BizHawk.Client.EmuHawk/AVOut/FFmpegWriter.cs

@@ -291,5 +291,8 @@ namespace BizHawk.Client.EmuHawk
 		{
 			token = FFmpegWriterForm.FormatPreset.GetDefaultPreset();
 		}
+
+		public bool UsesAudio { get { return true; } }
+		public bool UsesVideo { get { return true; } }
 	}
 }

BizHawk.Client.EmuHawk/AVOut/GifWriter.cs

@@ -227,5 +227,8 @@ namespace BizHawk.Client.EmuHawk
 				f = null;
 			}
 		}
+
+		public bool UsesAudio { get { return false; } }
+		public bool UsesVideo { get { return true; } }
 	}
 }

BizHawk.Client.EmuHawk/AVOut/IVideoWriter.cs

@@ -19,6 +19,15 @@ namespace BizHawk.Client.EmuHawk
 		/// </summary>
 		void SetDefaultVideoCodecToken();
 
+		/// <summary>
+		/// Returns whether this videowriter dumps audio
+		/// </summary>
+		bool UsesAudio { get; }
+
+		/// <summary>
+		/// Returns whether this videowriter dumps video
+		/// </summary>
+		bool UsesVideo { get; }
 
 		// why no OpenFile(IEnumerator<string>) ?
 		// different video writers may have different ideas of how and why splitting is to occur

BizHawk.Client.EmuHawk/AVOut/ImageSequenceWriter.cs

@@ -24,6 +24,8 @@ namespace BizHawk.Client.EmuHawk
 		{
 		}
 
+		public bool UsesAudio { get { return false; } }
+		public bool UsesVideo { get { return true; } }
 
 		public void OpenFile(string baseName)
 		{

BizHawk.Client.EmuHawk/AVOut/JMDWriter.cs

@@ -790,5 +790,10 @@ namespace BizHawk.Client.EmuHawk
 		}
 
 		public void SetFrame(int frame) { }
+
+		public bool UsesAudio { get { return true; } }
+		public bool UsesVideo { get { return true; } }
 	}
+
+
 }

BizHawk.Client.EmuHawk/AVOut/NutWriter.cs

@@ -138,5 +138,8 @@ namespace BizHawk.Client.EmuHawk
 		{
 			// ignored
 		}
+
+		public bool UsesAudio { get { return true; } }
+		public bool UsesVideo { get { return true; } }
 	}
 }

BizHawk.Client.EmuHawk/AVOut/SynclessRecorder.cs

@@ -68,6 +68,9 @@ namespace BizHawk.Client.EmuHawk
 			wwv.Dispose();
 		}
 
+		public bool UsesAudio { get { return true; } }
+		public bool UsesVideo { get { return true; } }
+
 		class DummyDisposable : IDisposable { public void Dispose() { } }
 
 		public IDisposable AcquireVideoCodecToken(IWin32Window hwnd) { return new DummyDisposable(); }

BizHawk.Client.EmuHawk/AVOut/WavWriter.cs

@@ -205,6 +205,9 @@ namespace BizHawk.Client.EmuHawk
 		public void SetVideoParameters(int width, int height) { }
 		public void SetFrame(int frame) { }
 
+		public bool UsesAudio { get { return true; } }
+		public bool UsesVideo { get { return false; } }
+
 		class WavWriterVToken : IDisposable
 		{
 			public void Dispose() { }

BizHawk.Client.EmuHawk/MainForm.cs

@@ -2817,8 +2817,10 @@ namespace BizHawk.Client.EmuHawk
 					coreskipaudio = true;
 
 				{
-					bool render = !_throttle.skipnextframe || _currAviWriter != null;
+					bool render = !_throttle.skipnextframe;
 					bool renderSound = !coreskipaudio;
+					if (_currAviWriter != null && _currAviWriter.UsesVideo) render = true;
+					if (_currAviWriter != null && _currAviWriter.UsesAudio) renderSound = true;
 					Global.Emulator.FrameAdvance(render, renderSound);
 				}