Merge pull request #17430 from jellyfin/drain-stderr

Drain stderr and stdout concurrently for encoder validation

MediaBrowser.MediaEncoding/Encoder/EncoderValidator.cs

@@ -8,6 +8,7 @@ using System.Linq;
 using System.Runtime.Versioning;
 using System.Text;
 using System.Text.RegularExpressions;
+using System.Threading.Tasks;
 using MediaBrowser.Controller.MediaEncoding;
 using Microsoft.Extensions.Logging;
 
@@ -662,8 +663,15 @@ namespace MediaBrowser.MediaEncoding.Encoder
                     writer.Write(testKey);
                 }
 
-                using var reader = readStdErr ? process.StandardError : process.StandardOutput;
-                return reader.ReadToEnd();
+                // Drain both streams concurrently to prevent pipe hanging, see #17429
+                using var standardOutput = process.StandardOutput;
+                using var standardError = process.StandardError;
+                var standardOutputTask = standardOutput.ReadToEndAsync();
+                var standardErrorTask = standardError.ReadToEndAsync();
+                process.WaitForExit();
+                Task.WaitAll(standardOutputTask, standardErrorTask);
+
+                return (readStdErr ? standardErrorTask : standardOutputTask).GetAwaiter().GetResult();
             }
         }