add image encoder based on ffmpeg

MediaBrowser.MediaEncoding/Encoder/ImageEncoder.cs

@@ -0,0 +1,158 @@
+using MediaBrowser.Controller.MediaEncoding;
+using MediaBrowser.Model.Logging;
+using System;
+using System.Diagnostics;
+using System.Globalization;
+using System.IO;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace MediaBrowser.MediaEncoding.Encoder
+{
+    public class ImageEncoder
+    {
+        private readonly string _ffmpegPath;
+        private readonly ILogger _logger;
+        private readonly CultureInfo _usCulture = new CultureInfo("en-US");
+
+        private static readonly SemaphoreSlim ResourcePool = new SemaphoreSlim(5, 5);
+
+        public ImageEncoder(string ffmpegPath, ILogger logger)
+        {
+            _ffmpegPath = ffmpegPath;
+            _logger = logger;
+        }
+
+        public async Task<Stream> EncodeImage(ImageEncodingOptions options, CancellationToken cancellationToken)
+        {
+            ValidateInput(options);
+
+            var process = new Process
+            {
+                StartInfo = new ProcessStartInfo
+                {
+                    CreateNoWindow = true,
+                    UseShellExecute = false,
+                    FileName = _ffmpegPath,
+                    Arguments = GetArguments(options),
+                    WindowStyle = ProcessWindowStyle.Hidden,
+                    ErrorDialog = false,
+                    RedirectStandardOutput = true,
+                    RedirectStandardError = true
+                }
+            };
+
+            await ResourcePool.WaitAsync(cancellationToken).ConfigureAwait(false);
+
+            process.Start();
+
+            var memoryStream = new MemoryStream();
+
+#pragma warning disable 4014
+            // Important - don't await the log task or we won't be able to kill ffmpeg when the user stops playback
+            process.StandardOutput.BaseStream.CopyToAsync(memoryStream);
+#pragma warning restore 4014
+
+            // MUST read both stdout and stderr asynchronously or a deadlock may occurr
+            process.BeginErrorReadLine();
+
+            var ranToCompletion = process.WaitForExit(5000);
+
+            if (!ranToCompletion)
+            {
+                try
+                {
+                    _logger.Info("Killing ffmpeg process");
+
+                    process.Kill();
+
+                    process.WaitForExit(1000);
+                }
+                catch (Exception ex)
+                {
+                    _logger.ErrorException("Error killing process", ex);
+                }
+            }
+
+            ResourcePool.Release();
+
+            var exitCode = ranToCompletion ? process.ExitCode : -1;
+
+            process.Dispose();
+
+            if (exitCode == -1 || memoryStream.Length == 0)
+            {
+                memoryStream.Dispose();
+
+                var msg = string.Format("ffmpeg image encoding failed for {0}", options.InputPath);
+
+                _logger.Error(msg);
+
+                throw new ApplicationException(msg);
+            }
+
+            memoryStream.Position = 0;
+            return memoryStream;
+        }
+
+        private string GetArguments(ImageEncodingOptions options)
+        {
+            var vfScale = GetFilterGraph(options);
+            var outputFormat = GetOutputFormat(options);
+
+            return string.Format("-i file:\"{0}\" {1} -f {2}",
+                options.InputPath,
+                vfScale,
+                outputFormat);
+        }
+
+        private string GetFilterGraph(ImageEncodingOptions options)
+        {
+            if (!options.Width.HasValue &&
+                !options.Height.HasValue &&
+                !options.MaxHeight.HasValue &&
+                !options.MaxWidth.HasValue)
+            {
+                return string.Empty;
+            }
+
+            var widthScale = "-1";
+            var heightScale = "-1";
+
+            if (options.MaxWidth.HasValue)
+            {
+                widthScale = "min(iw," + options.MaxWidth.Value.ToString(_usCulture) + ")";
+            }
+            else if (options.Width.HasValue)
+            {
+                widthScale = options.Width.Value.ToString(_usCulture);
+            }
+
+            if (options.MaxHeight.HasValue)
+            {
+                heightScale = "min(ih," + options.MaxHeight.Value.ToString(_usCulture) + ")";
+            }
+            else if (options.Height.HasValue)
+            {
+                heightScale = options.Height.Value.ToString(_usCulture);
+            }
+
+            var scaleMethod = "lanczos";
+
+            return string.Format("-vf scale=\"{0}:{1}\" -sws_flags {2}", 
+                widthScale, 
+                heightScale,
+                scaleMethod);
+        }
+
+        private string GetOutputFormat(ImageEncodingOptions options)
+        {
+            return options.Format;
+        }
+
+        private void ValidateInput(ImageEncodingOptions options)
+        {
+
+        }
+    }
+}