Allow fractional manual fps input, better err handling if encoding fails

Code/Data/Fraction.cs

@@ -219,6 +219,9 @@ namespace Flowframes.Data
 
         public float GetFloat()
         {
+            if (Denominator < 1)    // Avoid div by zero
+                return 0f;
+
             return (float)Numerator / (float)Denominator;
         }
 

Code/Form1.cs

@@ -280,22 +280,34 @@ namespace Flowframes
 
         private void fpsInTbox_TextChanged(object sender, EventArgs e)
         {
-            fpsInTbox.Text = fpsInTbox.Text.TrimNumbers(true);
+            UpdateUiFps();
-            UpdateOutputFPS();
         }
 
-        public void UpdateOutputFPS()
+        public void UpdateUiFps()
         {
-            float fpsOut = fpsInTbox.GetFloat() * interpFactorCombox.GetFloat();
+            if (fpsInTbox.Text.Contains("/"))   // Parse fraction
-            fpsOutTbox.Text = fpsOut.ToString();
+            {
+                string[] split = fpsInTbox.Text.Split('/');
+                Fraction frac = new Fraction(split[0].GetInt(), split[1].GetInt());
+                fpsInTbox.Text = frac.ToString();
+                fpsOutTbox.Text = (frac * interpFactorCombox.GetFloat()).ToString();
+
+                if (!fpsInTbox.ReadOnly)
+                    currInFps = frac;
+            }
+            else    // Parse float
+            {
+                fpsInTbox.Text = fpsInTbox.Text.TrimNumbers(true);
+                fpsOutTbox.Text = (fpsInTbox.GetFloat() * interpFactorCombox.GetFloat()).ToString();
 
                 if (!fpsInTbox.ReadOnly)
                     currInFps = new Fraction(fpsInTbox.GetFloat());
             }
+        }
 
         private void interpFactorCombox_SelectedIndexChanged(object sender, EventArgs e)
         {
-            UpdateOutputFPS();
+            UpdateUiFps();
             int guiInterpFactor = interpFactorCombox.GetInt();
             if (!initialized)
                 return;

Code/Main/CreateVideo.cs

@@ -218,6 +218,12 @@ namespace Flowframes.Main
 
         public static async Task MuxOutputVideo(string inputPath, string outVideo)
         {
+            if (!File.Exists(outVideo))
+            {
+                I.Cancel($"No video was encoded!\n\nFFmpeg Output:\n{AvProcess.lastOutputFfmpeg}");
+                return;
+            }
+
             if (!Config.GetBool("keepAudio") && !Config.GetBool("keepAudio"))
                 return;
 

Code/Main/InterpolateUtils.cs

@@ -323,7 +323,7 @@ namespace Flowframes.Main
             }
             if (passes && fpsOut.GetFloat() < 1f || fpsOut.GetFloat() > 1000f)
             {
-                ShowMessage("Invalid output frame rate - Must be 1-1000.");
+                ShowMessage($"Invalid output frame rate ({fpsOut.GetFloat()}).\nMust be 1-1000.");
                 passes = false;
             }
             if (!passes)