private async Task AcquireResources(StreamState state, CancellationTokenSource cancellationTokenSource)
        {
            if (state.VideoType == VideoType.Iso && state.IsoType.HasValue && IsoManager.CanMount(state.MediaPath))
            {
                state.IsoMount = await IsoManager.Mount(state.MediaPath, cancellationTokenSource.Token).ConfigureAwait(false);
            }

            if (state.MediaSource.RequiresOpening && string.IsNullOrWhiteSpace(state.Request.LiveStreamId))
            {
                var liveStreamResponse = await MediaSourceManager.OpenLiveStream(new LiveStreamRequest
                {
                    OpenToken = state.MediaSource.OpenToken

                }, false, cancellationTokenSource.Token).ConfigureAwait(false);

                AttachMediaSourceInfo(state, liveStreamResponse.MediaSource, state.VideoRequest, state.RequestedUrl);

                if (state.VideoRequest != null)
                {
                    TryStreamCopy(state, state.VideoRequest);
                }
            }

            if (state.MediaSource.BufferMs.HasValue)
            {
                await Task.Delay(state.MediaSource.BufferMs.Value, cancellationTokenSource.Token).ConfigureAwait(false);
            }
        }

        /// <summary>
        /// Starts the FFMPEG.
        /// </summary>
        /// <param name="state">The state.</param>
        /// <param name="outputPath">The output path.</param>
        /// <param name="cancellationTokenSource">The cancellation token source.</param>
        /// <returns>Task.</returns>
        /// <exception cref="System.InvalidOperationException">ffmpeg was not found at  + MediaEncoder.EncoderPath</exception>
        protected async Task StartFfMpeg(StreamState state, string outputPath, CancellationTokenSource cancellationTokenSource)
        {
            if (!File.Exists(MediaEncoder.EncoderPath))
            {
                throw new InvalidOperationException("ffmpeg was not found at " + MediaEncoder.EncoderPath);
            }

            Directory.CreateDirectory(Path.GetDirectoryName(outputPath));

            await AcquireResources(state, cancellationTokenSource).ConfigureAwait(false);

            var commandLineArgs = GetCommandLineArguments(outputPath, state, true);

            if (ServerConfigurationManager.Configuration.EnableDebugEncodingLogging)
            {
                commandLineArgs = "-loglevel debug " + commandLineArgs;
            }

            var process = new Process
            {
                StartInfo = new ProcessStartInfo
                {
                    CreateNoWindow = true,
                    UseShellExecute = false,

                    // Must consume both stdout and stderr or deadlocks may occur
                    RedirectStandardOutput = true,
                    RedirectStandardError = true,
                    RedirectStandardInput = true,

                    FileName = MediaEncoder.EncoderPath,
                    WorkingDirectory = Path.GetDirectoryName(MediaEncoder.EncoderPath),
                    Arguments = commandLineArgs,

                    WindowStyle = ProcessWindowStyle.Hidden,
                    ErrorDialog = false
                },

                EnableRaisingEvents = true
            };

            ApiEntryPoint.Instance.OnTranscodeBeginning(outputPath,
                TranscodingJobType,
                process,
                state.Request.DeviceId,
                state,
                cancellationTokenSource);

            var commandLineLogMessage = process.StartInfo.FileName + " " + process.StartInfo.Arguments;
            Logger.Info(commandLineLogMessage);

            var logFilePath = Path.Combine(ServerConfigurationManager.ApplicationPaths.LogDirectoryPath, "transcode-" + Guid.NewGuid() + ".txt");
            Directory.CreateDirectory(Path.GetDirectoryName(logFilePath));

            // FFMpeg writes debug/error info to stderr. This is useful when debugging so let's put it in the log directory.
            state.LogFileStream = FileSystem.GetFileStream(logFilePath, FileMode.Create, FileAccess.Write, FileShare.Read, true);

            var commandLineLogMessageBytes = Encoding.UTF8.GetBytes(commandLineLogMessage + Environment.NewLine + Environment.NewLine);
            await state.LogFileStream.WriteAsync(commandLineLogMessageBytes, 0, commandLineLogMessageBytes.Length, cancellationTokenSource.Token).ConfigureAwait(false);

            process.Exited += (sender, args) => OnFfMpegProcessExited(process, state, outputPath);

            try
            {
                process.Start();
            }
            catch (Exception ex)
            {
                Logger.ErrorException("Error starting ffmpeg", ex);

                ApiEntryPoint.Instance.OnTranscodeFailedToStart(outputPath, TranscodingJobType, state);

                throw;
            }

            // MUST read both stdout and stderr asynchronously or a deadlock may occurr
            process.BeginOutputReadLine();

            // Important - don't await the log task or we won't be able to kill ffmpeg when the user stops playback
            StartStreamingLog(state, process.StandardError.BaseStream, state.LogFileStream);

            // Wait for the file to exist before proceeeding
            while (!File.Exists(outputPath))
            {
                await Task.Delay(100, cancellationTokenSource.Token).ConfigureAwait(false);
            }
        }

 /// <summary>
 /// Gets the command line arguments.
 /// </summary>
 /// <param name="outputPath">The output path.</param>
 /// <param name="state">The state.</param>
 /// <param name="isEncoding">if set to <c>true</c> [is encoding].</param>
 /// <returns>System.String.</returns>
 protected abstract string GetCommandLineArguments(string outputPath, StreamState state, bool isEncoding);

        /// <summary>
        /// Gets the internal graphical subtitle param.
        /// </summary>
        /// <param name="state">The state.</param>
        /// <param name="outputVideoCodec">The output video codec.</param>
        /// <returns>System.String.</returns>
        protected string GetGraphicalSubtitleParam(StreamState state, string outputVideoCodec)
        {
            var outputSizeParam = string.Empty;

            var request = state.VideoRequest;

            // Add resolution params, if specified
            if (request.Width.HasValue || request.Height.HasValue || request.MaxHeight.HasValue || request.MaxWidth.HasValue)
            {
                outputSizeParam = GetOutputSizeParam(state, outputVideoCodec, CancellationToken.None).TrimEnd('"');
                outputSizeParam = "," + outputSizeParam.Substring(outputSizeParam.IndexOf("scale", StringComparison.OrdinalIgnoreCase));
            }

            var videoSizeParam = string.Empty;

            if (state.VideoStream != null && state.VideoStream.Width.HasValue && state.VideoStream.Height.HasValue)
            {
                videoSizeParam = string.Format(",scale={0}:{1}", state.VideoStream.Width.Value.ToString(UsCulture), state.VideoStream.Height.Value.ToString(UsCulture));
            }

            return string.Format(" -filter_complex \"[0:{0}]format=yuva444p{3},lut=u=128:v=128:y=gammaval(.3)[sub] ; [0:{1}] [sub] overlay{2}\"",
                state.SubtitleStream.Index,
                state.VideoStream.Index,
                outputSizeParam,
                videoSizeParam);
        }

        /// <summary>
        /// Gets the input argument.
        /// </summary>
        /// <param name="state">The state.</param>
        /// <returns>System.String.</returns>
        protected virtual string GetInputArgument(StreamState state)
        {
            var protocol = state.InputProtocol;

            var inputPath = new[] { state.MediaPath };

            if (state.IsInputVideo)
            {
                if (!(state.VideoType == VideoType.Iso && state.IsoMount == null))
                {
                    inputPath = MediaEncoderHelpers.GetInputArgument(state.MediaPath, state.InputProtocol, state.IsoMount, state.PlayableStreamFileNames);
                }
            }

            return MediaEncoder.GetInputArgument(inputPath, protocol);
        }

        /// <summary>
        /// Gets the video bitrate to specify on the command line
        /// </summary>
        /// <param name="state">The state.</param>
        /// <param name="videoCodec">The video codec.</param>
        /// <param name="isHls">if set to <c>true</c> [is HLS].</param>
        /// <returns>System.String.</returns>
        protected string GetVideoQualityParam(StreamState state, string videoCodec, bool isHls)
        {
            var param = string.Empty;

            var isVc1 = state.VideoStream != null &&
                string.Equals(state.VideoStream.Codec, "vc1", StringComparison.OrdinalIgnoreCase);

            var qualitySetting = GetQualitySetting();

            if (string.Equals(videoCodec, "libx264", StringComparison.OrdinalIgnoreCase))
            {
                switch (qualitySetting)
                {
                    case EncodingQuality.HighSpeed:
                        param = "-preset superfast";
                        break;
                    case EncodingQuality.HighQuality:
                        param = "-preset superfast";
                        break;
                    case EncodingQuality.MaxQuality:
                        param = "-preset superfast";
                        break;
                }

                switch (qualitySetting)
                {
                    case EncodingQuality.HighSpeed:
                        param += " -crf 23";
                        break;
                    case EncodingQuality.HighQuality:
                        param += " -crf 20";
                        break;
                    case EncodingQuality.MaxQuality:
                        param += " -crf 18";
                        break;
                }
            }

            // webm
            else if (string.Equals(videoCodec, "libvpx", StringComparison.OrdinalIgnoreCase))
            {
                // Values 0-3, 0 being highest quality but slower
                var profileScore = 0;

                string crf;

                switch (qualitySetting)
                {
                    case EncodingQuality.HighSpeed:
                        crf = "12";
                        profileScore = 2;
                        break;
                    case EncodingQuality.HighQuality:
                        crf = "8";
                        profileScore = 1;
                        break;
                    case EncodingQuality.MaxQuality:
                        crf = "4";
                        break;
                    default:
                        throw new ArgumentException("Unrecognized quality setting");
                }

                if (isVc1)
                {
                    profileScore++;
                    // Max of 2
                    profileScore = Math.Min(profileScore, 2);
                }

                // http://www.webmproject.org/docs/encoder-parameters/
                param = string.Format("-speed 16 -quality good -profile:v {0} -slices 8 -crf {1}",
                    profileScore.ToString(UsCulture),
                    crf);
            }

            else if (string.Equals(videoCodec, "mpeg4", StringComparison.OrdinalIgnoreCase))
            {
                param = "-mbd rd -flags +mv4+aic -trellis 2 -cmp 2 -subcmp 2 -bf 2";
            }

            // asf/wmv
            else if (string.Equals(videoCodec, "wmv2", StringComparison.OrdinalIgnoreCase))
            {
                param = "-qmin 2";
            }

            else if (string.Equals(videoCodec, "msmpeg4", StringComparison.OrdinalIgnoreCase))
            {
                param = "-mbd 2";
            }

            param += GetVideoBitrateParam(state, videoCodec, isHls);
//.........这里部分代码省略.........

        /// <summary>
        /// If we're going to put a fixed size on the command line, this will calculate it
        /// </summary>
        /// <param name="state">The state.</param>
        /// <param name="outputVideoCodec">The output video codec.</param>
        /// <param name="allowTimeStampCopy">if set to <c>true</c> [allow time stamp copy].</param>
        /// <param name="cancellationToken">The cancellation token.</param>
        /// <returns>System.String.</returns>
        protected string GetOutputSizeParam(StreamState state,
            string outputVideoCodec,
            CancellationToken cancellationToken,
            bool allowTimeStampCopy = true)
        {
            // http://sonnati.wordpress.com/2012/10/19/ffmpeg-the-swiss-army-knife-of-internet-streaming-part-vi/

            var request = state.VideoRequest;

            var filters = new List<string>();

            if (state.DeInterlace)
            {
                filters.Add("yadif=0:-1:0");
            }

            // If fixed dimensions were supplied
            if (request.Width.HasValue && request.Height.HasValue)
            {
                var widthParam = request.Width.Value.ToString(UsCulture);
                var heightParam = request.Height.Value.ToString(UsCulture);

                filters.Add(string.Format("scale=trunc({0}/2)*2:trunc({1}/2)*2", widthParam, heightParam));
            }

            // If Max dimensions were supplied, for width selects lowest even number between input width and width req size and selects lowest even number from in width*display aspect and requested size
            else if (request.MaxWidth.HasValue && request.MaxHeight.HasValue)
            {
                var maxWidthParam = request.MaxWidth.Value.ToString(UsCulture);
                var maxHeightParam = request.MaxHeight.Value.ToString(UsCulture);

                filters.Add(string.Format("scale=trunc(min(iw\\,{0})/2)*2:trunc(min((iw/dar)\\,{1})/2)*2", maxWidthParam, maxHeightParam));
            }

            // If a fixed width was requested
            else if (request.Width.HasValue)
            {
                var widthParam = request.Width.Value.ToString(UsCulture);

                filters.Add(string.Format("scale={0}:trunc(ow/a/2)*2", widthParam));
            }

            // If a fixed height was requested
            else if (request.Height.HasValue)
            {
                var heightParam = request.Height.Value.ToString(UsCulture);

                filters.Add(string.Format("scale=trunc(oh*a*2)/2:{0}", heightParam));
            }

            // If a max width was requested
            else if (request.MaxWidth.HasValue && (!request.MaxHeight.HasValue || state.VideoStream == null))
            {
                var maxWidthParam = request.MaxWidth.Value.ToString(UsCulture);

                filters.Add(string.Format("scale=min(iw\\,{0}):trunc(ow/dar/2)*2", maxWidthParam));
            }

            // If a max height was requested
            else if (request.MaxHeight.HasValue && (!request.MaxWidth.HasValue || state.VideoStream == null))
            {
                var maxHeightParam = request.MaxHeight.Value.ToString(UsCulture);

                filters.Add(string.Format("scale=trunc(oh*a*2)/2:min(ih\\,{0})", maxHeightParam));
            }

            else if (request.MaxWidth.HasValue ||
                request.MaxHeight.HasValue ||
                request.Width.HasValue ||
                request.Height.HasValue)
            {
                if (state.VideoStream != null)
                {
                    // Need to perform calculations manually

                    // Try to account for bad media info
                    var currentHeight = state.VideoStream.Height ?? request.MaxHeight ?? request.Height ?? 0;
                    var currentWidth = state.VideoStream.Width ?? request.MaxWidth ?? request.Width ?? 0;

                    var outputSize = DrawingUtils.Resize(currentWidth, currentHeight, request.Width, request.Height, request.MaxWidth, request.MaxHeight);

                    var manualWidthParam = outputSize.Width.ToString(UsCulture);
                    var manualHeightParam = outputSize.Height.ToString(UsCulture);

                    filters.Add(string.Format("scale=trunc({0}/2)*2:trunc({1}/2)*2", manualWidthParam, manualHeightParam));
                }
            }

            var output = string.Empty;

            if (state.SubtitleStream != null && state.SubtitleStream.IsTextSubtitleStream)
            {
//.........这里部分代码省略.........

        protected double? GetFramerateParam(StreamState state)
        {
            if (state.VideoRequest != null)
            {
                if (state.VideoRequest.Framerate.HasValue)
                {
                    return state.VideoRequest.Framerate.Value;
                }

                var maxrate = state.VideoRequest.MaxFramerate ?? 23.97602;

                if (state.VideoStream != null)
                {
                    var contentRate = state.VideoStream.AverageFrameRate ?? state.VideoStream.RealFrameRate;

                    if (contentRate.HasValue && contentRate.Value > maxrate)
                    {
                        return maxrate;
                    }
                }
            }

            return null;
        }

        /// <summary>
        /// Gets the output file path.
        /// </summary>
        /// <param name="state">The state.</param>
        /// <returns>System.String.</returns>
        private string GetOutputFilePath(StreamState state)
        {
            var folder = ServerConfigurationManager.ApplicationPaths.TranscodingTempPath;

            var outputFileExtension = GetOutputFileExtension(state);

            var data = GetCommandLineArguments("dummy\\dummy", state, false);

            data += "-" + (state.Request.DeviceId ?? string.Empty);

            return Path.Combine(folder, data.GetMD5().ToString("N") + (outputFileExtension ?? string.Empty).ToLower());
        }

        /// <summary>
        /// Gets the user agent param.
        /// </summary>
        /// <param name="state">The state.</param>
        /// <returns>System.String.</returns>
        private string GetUserAgentParam(StreamState state)
        {
            string useragent = null;

            state.RemoteHttpHeaders.TryGetValue("User-Agent", out useragent);

            if (!string.IsNullOrWhiteSpace(useragent))
            {
                return "-user-agent \"" + useragent + "\"";
            }

            return string.Empty;
        }

        /// <summary>
        /// Processes the exited.
        /// </summary>
        /// <param name="process">The process.</param>
        /// <param name="state">The state.</param>
        /// <param name="outputPath">The output path.</param>
        private void OnFfMpegProcessExited(Process process, StreamState state, string outputPath)
        {
            var job = ApiEntryPoint.Instance.GetTranscodingJob(outputPath, TranscodingJobType);

            if (job != null)
            {
                job.HasExited = true;
            }

            Logger.Debug("Disposing stream resources");
            state.Dispose();

            try
            {
                Logger.Info("FFMpeg exited with code {0}", process.ExitCode);
            }
            catch
            {
                Logger.Error("FFMpeg exited with an error.");
            }

            // This causes on exited to be called twice:
            //try
            //{
            //    // Dispose the process
            //    process.Dispose();
            //}
            //catch (Exception ex)
            //{
            //    Logger.ErrorException("Error disposing ffmpeg.", ex);
            //}
        }

 /// <summary>
 /// Gets the output file extension.
 /// </summary>
 /// <param name="state">The state.</param>
 /// <returns>System.String.</returns>
 protected virtual string GetOutputFileExtension(StreamState state)
 {
     return Path.GetExtension(state.RequestedUrl);
 }

        protected string GetVideoBitrateParam(StreamState state, string videoCodec, bool isHls)
        {
            var bitrate = state.OutputVideoBitrate;

            if (bitrate.HasValue)
            {
                var hasFixedResolution = state.VideoRequest.HasFixedResolution;

                if (string.Equals(videoCodec, "libvpx", StringComparison.OrdinalIgnoreCase))
                {
                    if (hasFixedResolution)
                    {
                        return string.Format(" -minrate:v ({0}*.90) -maxrate:v ({0}*1.10) -bufsize:v {0} -b:v {0}", bitrate.Value.ToString(UsCulture));
                    }

                    // With vpx when crf is used, b:v becomes a max rate
                    // https://trac.ffmpeg.org/wiki/vpxEncodingGuide. But higher bitrate source files -b:v causes judder so limite the bitrate but dont allow it to "saturate" the bitrate. So dont contrain it down just up.
                    return string.Format(" -maxrate:v {0} -bufsize:v ({0}*2) -b:v {0}", bitrate.Value.ToString(UsCulture));
                }

                if (string.Equals(videoCodec, "msmpeg4", StringComparison.OrdinalIgnoreCase))
                {
                    return string.Format(" -b:v {0}", bitrate.Value.ToString(UsCulture));
                }

                // H264
                if (hasFixedResolution)
                {
                    if (isHls)
                    {
                        return string.Format(" -b:v {0} -maxrate ({0}*.80) -bufsize {0}", bitrate.Value.ToString(UsCulture));
                    }

                    return string.Format(" -b:v {0}", bitrate.Value.ToString(UsCulture));
                }

                return string.Format(" -maxrate {0} -bufsize {1}",
                    bitrate.Value.ToString(UsCulture),
                    (bitrate.Value * 2).ToString(UsCulture));
            }

            return string.Empty;
        }

        /// <summary>
        /// Starts the FFMPEG.
        /// </summary>
        /// <param name="state">The state.</param>
        /// <param name="outputPath">The output path.</param>
        /// <param name="cancellationTokenSource">The cancellation token source.</param>
        /// <param name="workingDirectory">The working directory.</param>
        /// <returns>Task.</returns>
        protected async Task<TranscodingJob> StartFfMpeg(StreamState state,
            string outputPath,
            CancellationTokenSource cancellationTokenSource,
            string workingDirectory = null)
        {
            FileSystem.CreateDirectory(Path.GetDirectoryName(outputPath));

            await AcquireResources(state, cancellationTokenSource).ConfigureAwait(false);

            var transcodingId = Guid.NewGuid().ToString("N");
            var commandLineArgs = GetCommandLineArguments(outputPath, state, true);

            if (ApiEntryPoint.Instance.GetEncodingOptions().EnableDebugLogging)
            {
                commandLineArgs = "-loglevel debug " + commandLineArgs;
            }

            var process = new Process
            {
                StartInfo = new ProcessStartInfo
                {
                    CreateNoWindow = true,
                    UseShellExecute = false,

                    // Must consume both stdout and stderr or deadlocks may occur
                    RedirectStandardOutput = true,
                    RedirectStandardError = true,
                    RedirectStandardInput = true,

                    FileName = MediaEncoder.EncoderPath,
                    Arguments = commandLineArgs,

                    WindowStyle = ProcessWindowStyle.Hidden,
                    ErrorDialog = false
                },

                EnableRaisingEvents = true
            };

            if (!string.IsNullOrWhiteSpace(workingDirectory))
            {
                process.StartInfo.WorkingDirectory = workingDirectory;
            }

            var transcodingJob = ApiEntryPoint.Instance.OnTranscodeBeginning(outputPath,
                state.Request.PlaySessionId,
                state.MediaSource.LiveStreamId,
                transcodingId,
                TranscodingJobType,
                process,
                state.Request.DeviceId,
                state,
                cancellationTokenSource);

            var commandLineLogMessage = process.StartInfo.FileName + " " + process.StartInfo.Arguments;
            Logger.Info(commandLineLogMessage);

            var logFilePath = Path.Combine(ServerConfigurationManager.ApplicationPaths.LogDirectoryPath, "transcode-" + Guid.NewGuid() + ".txt");
            FileSystem.CreateDirectory(Path.GetDirectoryName(logFilePath));

            // FFMpeg writes debug/error info to stderr. This is useful when debugging so let's put it in the log directory.
            state.LogFileStream = FileSystem.GetFileStream(logFilePath, FileMode.Create, FileAccess.Write, FileShare.Read, true);

            var commandLineLogMessageBytes = Encoding.UTF8.GetBytes(Request.AbsoluteUri + Environment.NewLine + Environment.NewLine + JsonSerializer.SerializeToString(state.MediaSource) + Environment.NewLine + Environment.NewLine + commandLineLogMessage + Environment.NewLine + Environment.NewLine);
            await state.LogFileStream.WriteAsync(commandLineLogMessageBytes, 0, commandLineLogMessageBytes.Length, cancellationTokenSource.Token).ConfigureAwait(false);

            process.Exited += (sender, args) => OnFfMpegProcessExited(process, transcodingJob, state);

            try
            {
                process.Start();
            }
            catch (Exception ex)
            {
                Logger.ErrorException("Error starting ffmpeg", ex);

                ApiEntryPoint.Instance.OnTranscodeFailedToStart(outputPath, TranscodingJobType, state);

                throw;
            }

            // MUST read both stdout and stderr asynchronously or a deadlock may occurr
            process.BeginOutputReadLine();

            // Important - don't await the log task or we won't be able to kill ffmpeg when the user stops playback
            StartStreamingLog(transcodingJob, state, process.StandardError.BaseStream, state.LogFileStream);

            // Wait for the file to exist before proceeeding
			while (!FileSystem.FileExists(state.WaitForPath ?? outputPath) && !transcodingJob.HasExited)
            {
                await Task.Delay(100, cancellationTokenSource.Token).ConfigureAwait(false);
            }
//.........这里部分代码省略.........

        protected string GetInputModifier(StreamState state, bool genPts = true)
        {
            var inputModifier = string.Empty;

            var probeSize = GetProbeSizeArgument(state);
            inputModifier += " " + probeSize;
            inputModifier = inputModifier.Trim();

            var userAgentParam = GetUserAgentParam(state);

            if (!string.IsNullOrWhiteSpace(userAgentParam))
            {
                inputModifier += " " + userAgentParam;
            }

            inputModifier = inputModifier.Trim();

            inputModifier += " " + GetFastSeekCommandLineParameter(state.Request);
            inputModifier = inputModifier.Trim();

            if (state.VideoRequest != null && genPts)
            {
                inputModifier += " -fflags +genpts";
            }

            if (!string.IsNullOrEmpty(state.InputAudioSync))
            {
                inputModifier += " -async " + state.InputAudioSync;
            }

            if (!string.IsNullOrEmpty(state.InputVideoSync))
            {
                inputModifier += " -vsync " + state.InputVideoSync;
            }

            if (state.ReadInputAtNativeFramerate)
            {
                inputModifier += " -re";
            }

            return inputModifier;
        }

        /// <summary>
        /// Gets the state.
        /// </summary>
        /// <param name="request">The request.</param>
        /// <param name="cancellationToken">The cancellation token.</param>
        /// <returns>StreamState.</returns>
        protected async Task<StreamState> GetState(StreamRequest request, CancellationToken cancellationToken)
        {
            ParseDlnaHeaders(request);

            if (!string.IsNullOrWhiteSpace(request.Params))
            {
                ParseParams(request);
            }

            var url = Request.PathInfo;

            if (string.IsNullOrEmpty(request.AudioCodec))
            {
                request.AudioCodec = InferAudioCodec(url);
            }

            var state = new StreamState(LiveTvManager, Logger)
            {
                Request = request,
                RequestedUrl = url
            };

            if (!string.IsNullOrWhiteSpace(request.AudioCodec))
            {
                state.SupportedAudioCodecs = request.AudioCodec.Split(',').Where(i => !string.IsNullOrWhiteSpace(i)).ToList();
                state.Request.AudioCodec = state.SupportedAudioCodecs.FirstOrDefault();
            }

            var item = LibraryManager.GetItemById(request.Id);

            List<MediaStream> mediaStreams = null;

            state.ItemType = item.GetType().Name;

            if (item is ILiveTvRecording)
            {
                var recording = await LiveTvManager.GetInternalRecording(request.Id, cancellationToken).ConfigureAwait(false);

                state.VideoType = VideoType.VideoFile;
                state.IsInputVideo = string.Equals(recording.MediaType, MediaType.Video, StringComparison.OrdinalIgnoreCase);

                var path = recording.RecordingInfo.Path;
                var mediaUrl = recording.RecordingInfo.Url;

                var source = string.IsNullOrEmpty(request.MediaSourceId)
                    ? recording.GetMediaSources(false).First()
                    : recording.GetMediaSources(false).First(i => string.Equals(i.Id, request.MediaSourceId));

                mediaStreams = source.MediaStreams;

                // Just to prevent this from being null and causing other methods to fail
                state.MediaPath = string.Empty;

                if (!string.IsNullOrEmpty(path))
                {
                    state.MediaPath = path;
                    state.InputProtocol = MediaProtocol.File;
                }
                else if (!string.IsNullOrEmpty(mediaUrl))
                {
                    state.MediaPath = mediaUrl;
                    state.InputProtocol = MediaProtocol.Http;
                }
                else
                {
                    // No media info, so this is probably needed
                    state.DeInterlace = true;
                }

                if (recording.RecordingInfo.Status == RecordingStatus.InProgress)
                {
                    state.ReadInputAtNativeFramerate = true;
                }

                state.RunTimeTicks = recording.RunTimeTicks;

                state.OutputAudioSync = "1000";
                state.InputVideoSync = "-1";
                state.InputAudioSync = "1";
                state.InputContainer = recording.Container;
            }
            else if (item is LiveTvChannel)
            {
                var channel = LiveTvManager.GetInternalChannel(request.Id);

                state.VideoType = VideoType.VideoFile;
                state.IsInputVideo = string.Equals(channel.MediaType, MediaType.Video, StringComparison.OrdinalIgnoreCase);
                mediaStreams = new List<MediaStream>();

                state.ReadInputAtNativeFramerate = true;
                state.OutputAudioSync = "1000";
                state.DeInterlace = true;
                state.InputVideoSync = "-1";
                state.InputAudioSync = "1";
//.........这里部分代码省略.........

        /// <summary>
        /// Gets the number of threads.
        /// </summary>
        /// <returns>System.Int32.</returns>
        /// <exception cref="System.Exception">Unrecognized MediaEncodingQuality value.</exception>
        protected int GetNumberOfThreads(StreamState state, bool isWebm)
        {
            // Use more when this is true. -re will keep cpu usage under control
            if (state.ReadInputAtNativeFramerate)
            {
                if (isWebm)
                {
                    return Math.Max(Environment.ProcessorCount - 1, 2);
                }

                return 0;
            }

            // Webm: http://www.webmproject.org/docs/encoder-parameters/
            // The decoder will usually automatically use an appropriate number of threads according to how many cores are available but it can only use multiple threads 
            // for the coefficient data if the encoder selected --token-parts > 0 at encode time.

            switch (GetQualitySetting())
            {
                case EncodingQuality.HighSpeed:
                    return 2;
                case EncodingQuality.HighQuality:
                    return 2;
                case EncodingQuality.MaxQuality:
                    return isWebm ? Math.Max(Environment.ProcessorCount - 1, 2) : 0;
                default:
                    throw new Exception("Unrecognized MediaEncodingQuality value.");
            }
        }

        /// <summary>
        /// Gets the map args.
        /// </summary>
        /// <param name="state">The state.</param>
        /// <returns>System.String.</returns>
        protected virtual string GetMapArgs(StreamState state)
        {
            // If we don't have known media info
            // If input is video, use -sn to drop subtitles
            // Otherwise just return empty
            if (state.VideoStream == null && state.AudioStream == null)
            {
                return state.IsInputVideo ? "-sn" : string.Empty;
            }

            // We have media info, but we don't know the stream indexes
            if (state.VideoStream != null && state.VideoStream.Index == -1)
            {
                return "-sn";
            }

            // We have media info, but we don't know the stream indexes
            if (state.AudioStream != null && state.AudioStream.Index == -1)
            {
                return state.IsInputVideo ? "-sn" : string.Empty;
            }

            var args = string.Empty;

            if (state.VideoStream != null)
            {
                args += string.Format("-map 0:{0}", state.VideoStream.Index);
            }
            else
            {
                args += "-map -0:v";
            }

            if (state.AudioStream != null)
            {
                args += string.Format(" -map 0:{0}", state.AudioStream.Index);
            }

            else
            {
                args += " -map -0:a";
            }

            if (state.SubtitleStream == null)
            {
                args += " -map -0:s";
            }

            return args;
        }

        protected string GetAudioFilterParam(StreamState state, bool isHls)
        {
            var volParam = string.Empty;
            var audioSampleRate = string.Empty;

            var channels = state.OutputAudioChannels;

            // Boost volume to 200% when downsampling from 6ch to 2ch
            if (channels.HasValue && channels.Value <= 2)
            {
                if (state.AudioStream != null && state.AudioStream.Channels.HasValue && state.AudioStream.Channels.Value > 5)
                {
                    volParam = ",volume=" + ServerConfigurationManager.Configuration.DownMixAudioBoost.ToString(UsCulture);
                }
            }

            if (state.OutputAudioSampleRate.HasValue)