1 files changed, 159 insertions, 0 deletions
diff --git a/MediaBrowser.Api/Playback/TranscodingThrottler.cs b/MediaBrowser.Api/Playback/TranscodingThrottler.cs
new file mode 100644
index 000000000..943a4d065
--- /dev/null
+++ b/MediaBrowser.Api/Playback/TranscodingThrottler.cs
@@ -0,0 +1,159 @@
+using MediaBrowser.Controller.Diagnostics;
+using MediaBrowser.Model.Logging;
+using System;
+using System.IO;
+using System.Threading;
+
+namespace MediaBrowser.Api.Playback
+{
+    public class TranscodingThrottler : IDisposable
+    {
+        private readonly TranscodingJob _job;
+        private readonly ILogger _logger;
+        private readonly IProcessManager _processManager;
+        private Timer _timer;
+        private bool _isPaused;
+
+        private readonly long _gapLengthInTicks = TimeSpan.FromMinutes(2).Ticks;
+
+        public TranscodingThrottler(TranscodingJob job, ILogger logger, IProcessManager processManager)
+        {
+            _job = job;
+            _logger = logger;
+            _processManager = processManager;
+        }
+
+        public void Start()
+        {
+            _timer = new Timer(TimerCallback, null, 5000, 5000);
+        }
+
+        private void TimerCallback(object state)
+        {
+            if (_job.HasExited)
+            {
+                DisposeTimer();
+                return;
+            }
+
+            if (IsThrottleAllowed(_job))
+            {
+                PauseTranscoding();
+            }
+            else
+            {
+                UnpauseTranscoding();
+            }
+        }
+
+        private void PauseTranscoding()
+        {
+            if (!_isPaused)
+            {
+                _logger.Debug("Sending pause command to ffmpeg");
+
+                try
+                {
+                    _job.Process.StandardInput.Write("c");
+                    _isPaused = true;
+                }
+                catch (Exception ex)
+                {
+                    _logger.ErrorException("Error pausing transcoding", ex);
+                }
+            }
+        }
+
+        private void UnpauseTranscoding()
+        {
+            if (_isPaused)
+            {
+                _logger.Debug("Sending unpause command to ffmpeg");
+
+                try
+                {
+                    _job.Process.StandardInput.WriteLine();
+                    _isPaused = false;
+                }
+                catch (Exception ex)
+                {
+                    _logger.ErrorException("Error unpausing transcoding", ex);
+                }
+            }
+        }
+
+        private bool IsThrottleAllowed(TranscodingJob job)
+        {
+            var bytesDownloaded = job.BytesDownloaded ?? 0;
+            var transcodingPositionTicks = job.TranscodingPositionTicks ?? 0;
+            var downloadPositionTicks = job.DownloadPositionTicks ?? 0;
+
+            var path = job.Path;
+
+            if (downloadPositionTicks > 0 && transcodingPositionTicks > 0)
+            {
+                // HLS - time-based consideration
+
+                var targetGap = _gapLengthInTicks;
+                var gap = transcodingPositionTicks - downloadPositionTicks;
+
+                if (gap < targetGap)
+                {
+                    //_logger.Debug("Not throttling transcoder gap {0} target gap {1}", gap, targetGap);
+                    return false;
+                }
+
+                //_logger.Debug("Throttling transcoder gap {0} target gap {1}", gap, targetGap);
+                return true;
+            }
+
+            if (bytesDownloaded > 0 && transcodingPositionTicks > 0)
+            {
+                // Progressive Streaming - byte-based consideration
+
+                try
+                {
+                    var bytesTranscoded = job.BytesTranscoded ?? new FileInfo(path).Length;
+
+                    // Estimate the bytes the transcoder should be ahead
+                    double gapFactor = _gapLengthInTicks;
+                    gapFactor /= transcodingPositionTicks;
+                    var targetGap = bytesTranscoded * gapFactor;
+
+                    var gap = bytesTranscoded - bytesDownloaded;
+
+                    if (gap < targetGap)
+                    {
+                        //_logger.Debug("Not throttling transcoder gap {0} target gap {1} bytes downloaded {2}", gap, targetGap, bytesDownloaded);
+                        return false;
+                    }
+
+                    //_logger.Debug("Throttling transcoder gap {0} target gap {1} bytes downloaded {2}", gap, targetGap, bytesDownloaded);
+                    return true;
+                }
+                catch
+                {
+                    //_logger.Error("Error getting output size");
+                    return false;
+                }
+            }
+
+            //_logger.Debug("No throttle data for " + path);
+            return false;
+        }
+
+        public void Dispose()
+        {
+            DisposeTimer();
+        }
+
+        private void DisposeTimer()
+        {
+            if (_timer != null)
+            {
+                _timer.Dispose();
+                _timer = null;
+            }
+        }
+    }
+}