From 1204e4ae9b0d5114157422457147ba09c97169ce Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Melvyn=20La=C3=AFly?= <melvyn.laily@gmail.com>
Date: Sun, 22 Apr 2018 17:26:32 +0200
Subject: [PATCH] Fix some bugs

---
 MovieBarCodeGenerator/FfmpegWrapper.cs | 24 +++++++++++++++++++-----
 MovieBarCodeGenerator/MainForm.cs      |  1 +
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/MovieBarCodeGenerator/FfmpegWrapper.cs b/MovieBarCodeGenerator/FfmpegWrapper.cs
index 94a6685..31472bb 100644
--- a/MovieBarCodeGenerator/FfmpegWrapper.cs
+++ b/MovieBarCodeGenerator/FfmpegWrapper.cs
@@ -20,7 +20,7 @@ public FfmpegWrapper(string ffmpegExecutablePath)
             FfmpegExecutablePath = ffmpegExecutablePath;
         }
 
-        private Process StartFfmpegInstance(string args)
+        private Process StartFfmpegInstance(string args, bool redirectError = false)
         {
             try
             {
@@ -28,8 +28,11 @@ private Process StartFfmpegInstance(string args)
                 {
                     FileName = FfmpegExecutablePath,
                     Arguments = args,
+                    // Warning: if a standard stread is redirected but is not read,
+                    // its buffer might fill up and block the whole process.
+                    // Only redirect a standard stream if you read it!
                     RedirectStandardOutput = true,
-                    RedirectStandardError = true,
+                    RedirectStandardError = redirectError,
                     UseShellExecute = false,
                     CreateNoWindow = true,
                 });
@@ -45,12 +48,14 @@ public TimeSpan GetMediaDuration(string inputPath, CancellationToken cancellatio
         {
             var args = $"-i \"{inputPath}\"";
 
-            var process = StartFfmpegInstance(args);
+            var process = StartFfmpegInstance(args, redirectError: true);
 
             using (cancellationToken.Register(() => process.Kill()))
             {
                 var output = process.StandardError.ReadToEnd();
 
+                cancellationToken.ThrowIfCancellationRequested();
+
                 var match = Regex.Match(output, @"Duration: (.*?),");
                 if (match.Success)
                 {
@@ -75,10 +80,19 @@ public IEnumerable<Bitmap> GetImagesFromMedia(string inputPath, int frameCount,
 
             var process = StartFfmpegInstance(args);
 
-            using (cancellationToken.Register(() => process.Kill()))
+            IEnumerable<Bitmap> GetLazyStream()
             {
-                return ReadBitmapStream(process.StandardOutput.BaseStream);
+                using (cancellationToken.Register(() => process.Kill()))
+                {
+                    foreach (var item in ReadBitmapStream(process.StandardOutput.BaseStream))
+                    {
+                        yield return item;
+                    }
+                    cancellationToken.ThrowIfCancellationRequested();
+                }
             }
+
+            return GetLazyStream();
         }
 
         private IEnumerable<Bitmap> ReadBitmapStream(Stream stdout)
diff --git a/MovieBarCodeGenerator/MainForm.cs b/MovieBarCodeGenerator/MainForm.cs
index 07f7671..3a62b2f 100644
--- a/MovieBarCodeGenerator/MainForm.cs
+++ b/MovieBarCodeGenerator/MainForm.cs
@@ -61,6 +61,7 @@ private async void generateButton_Click(object sender, EventArgs e)
                 _cancellationTokenSource.Cancel();
                 _cancellationTokenSource = null;
                 generateButton.Text = GenerateButtonText;
+                progressBar1.Value = progressBar1.Minimum;
                 return;
             }