public async Task<EncodingJob> CreateJob(EncodingJobOptions options, bool isVideoRequest, IProgress<double> progress, CancellationToken cancellationToken)
        {
            var request = options;

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

            var state = new EncodingJob(_logger, _mediaSourceManager)
            {
                Options = options,
                IsVideoRequest = isVideoRequest,
                Progress = progress
            };

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

            var item = _libraryManager.GetItemById(request.ItemId);
            state.ItemType = item.GetType().Name;

            state.IsInputVideo = string.Equals(item.MediaType, MediaType.Video, StringComparison.OrdinalIgnoreCase);

            var mediaSources = await _mediaSourceManager.GetPlayackMediaSources(request.ItemId, null, false, new[] { MediaType.Audio, MediaType.Video }, cancellationToken).ConfigureAwait(false);

            var mediaSource = string.IsNullOrEmpty(request.MediaSourceId)
               ? mediaSources.First()
               : mediaSources.First(i => string.Equals(i.Id, request.MediaSourceId));

            AttachMediaStreamInfo(state, mediaSource, options);

            state.OutputAudioBitrate = GetAudioBitrateParam(request, state.AudioStream);
            state.OutputAudioSampleRate = request.AudioSampleRate;

            state.OutputAudioCodec = GetAudioCodec(request);

            state.OutputAudioChannels = GetNumAudioChannelsParam(request, state.AudioStream, state.OutputAudioCodec);

            if (isVideoRequest)
            {
                state.OutputVideoCodec = GetVideoCodec(request);
                state.OutputVideoBitrate = GetVideoBitrateParamValue(request, state.VideoStream);

                if (state.OutputVideoBitrate.HasValue)
                {
                    var resolution = ResolutionNormalizer.Normalize(state.OutputVideoBitrate.Value,
                        state.OutputVideoCodec,
                        request.MaxWidth,
                        request.MaxHeight);

                    request.MaxWidth = resolution.MaxWidth;
                    request.MaxHeight = resolution.MaxHeight;
                }
            }

            ApplyDeviceProfileSettings(state);

            TryStreamCopy(state, request);

            return state;
        }

        /// <summary>
        /// Enforces the resolution limit.
        /// </summary>
        /// <param name="state">The state.</param>
        /// <param name="videoRequest">The video request.</param>
        private static void EnforceResolutionLimit(EncodingJob state, EncodingJobOptions videoRequest)
        {
            // Switch the incoming params to be ceilings rather than fixed values
            videoRequest.MaxWidth = videoRequest.MaxWidth ?? videoRequest.Width;
            videoRequest.MaxHeight = videoRequest.MaxHeight ?? videoRequest.Height;

            videoRequest.Width = null;
            videoRequest.Height = null;
        }

        /// <summary>
        /// Gets the number of audio channels to specify on the command line
        /// </summary>
        /// <param name="request">The request.</param>
        /// <param name="audioStream">The audio stream.</param>
        /// <param name="outputAudioCodec">The output audio codec.</param>
        /// <returns>System.Nullable{System.Int32}.</returns>
        private int? GetNumAudioChannelsParam(EncodingJobOptions request, MediaStream audioStream, string outputAudioCodec)
        {
            var inputChannels = audioStream == null
                            ? null
                            : audioStream.Channels;

            if (inputChannels <= 0)
            {
                inputChannels = null;
            }

            var codec = outputAudioCodec ?? string.Empty;

            if (codec.IndexOf("wma", StringComparison.OrdinalIgnoreCase) != -1)
            {
                // wmav2 currently only supports two channel output
                return Math.Min(2, inputChannels ?? 2);
            }

            if (request.MaxAudioChannels.HasValue)
            {
                if (inputChannels.HasValue)
                {
                    return Math.Min(request.MaxAudioChannels.Value, inputChannels.Value);
                }

                var channelLimit = codec.IndexOf("mp3", StringComparison.OrdinalIgnoreCase) != -1
                    ? 2
                    : 6;

                // If we don't have any media info then limit it to 5 to prevent encoding errors due to asking for too many channels
                return Math.Min(request.MaxAudioChannels.Value, channelLimit);
            }

            return request.AudioChannels;
        }

        private int? GetVideoBitrateParamValue(EncodingJobOptions request, MediaStream videoStream, string outputVideoCodec)
        {
            var bitrate = request.VideoBitRate;

            if (videoStream != null)
            {
                var isUpscaling = request.Height.HasValue && videoStream.Height.HasValue &&
                                   request.Height.Value > videoStream.Height.Value;

                if (request.Width.HasValue && videoStream.Width.HasValue &&
                    request.Width.Value > videoStream.Width.Value)
                {
                    isUpscaling = true;
                }

                // Don't allow bitrate increases unless upscaling
                if (!isUpscaling)
                {
                    if (bitrate.HasValue && videoStream.BitRate.HasValue)
                    {
                        bitrate = Math.Min(bitrate.Value, videoStream.BitRate.Value);
                    }
                }
            }

            if (bitrate.HasValue)
            {
                var inputVideoCodec = videoStream == null ? null : videoStream.Codec;
                bitrate = ResolutionNormalizer.ScaleBitrate(bitrate.Value, inputVideoCodec, outputVideoCodec);

                // If a max bitrate was requested, don't let the scaled bitrate exceed it
                if (request.VideoBitRate.HasValue)
                {
                    bitrate = Math.Min(bitrate.Value, request.VideoBitRate.Value);
                }
            }

            return bitrate;
        }

        internal static void AttachMediaStreamInfo(EncodingJob state,
            MediaSourceInfo mediaSource,
            EncodingJobOptions videoRequest)
        {
            state.MediaPath = mediaSource.Path;
            state.InputProtocol = mediaSource.Protocol;
            state.InputContainer = mediaSource.Container;
            state.InputFileSize = mediaSource.Size;
            state.InputBitrate = mediaSource.Bitrate;
            state.RunTimeTicks = mediaSource.RunTimeTicks;
            state.RemoteHttpHeaders = mediaSource.RequiredHttpHeaders;

            if (mediaSource.ReadAtNativeFramerate)
            {
                state.ReadInputAtNativeFramerate = true;
            }

            if (mediaSource.VideoType.HasValue)
            {
                state.VideoType = mediaSource.VideoType.Value;
            }

            state.IsoType = mediaSource.IsoType;

            state.PlayableStreamFileNames = mediaSource.PlayableStreamFileNames.ToList();

            if (mediaSource.Timestamp.HasValue)
            {
                state.InputTimestamp = mediaSource.Timestamp.Value;
            }

            state.InputProtocol = mediaSource.Protocol;
            state.MediaPath = mediaSource.Path;
            state.RunTimeTicks = mediaSource.RunTimeTicks;
            state.RemoteHttpHeaders = mediaSource.RequiredHttpHeaders;
            state.InputBitrate = mediaSource.Bitrate;
            state.InputFileSize = mediaSource.Size;

            if (state.ReadInputAtNativeFramerate ||
                mediaSource.Protocol == MediaProtocol.File && string.Equals(mediaSource.Container, "wtv", StringComparison.OrdinalIgnoreCase))
            {
                state.OutputAudioSync = "1000";
                state.InputVideoSync = "-1";
                state.InputAudioSync = "1";
            }

            var mediaStreams = mediaSource.MediaStreams;

            if (videoRequest != null)
            {
                if (string.IsNullOrEmpty(videoRequest.VideoCodec))
                {
                    videoRequest.VideoCodec = InferVideoCodec(videoRequest.OutputContainer);
                }

                state.VideoStream = GetMediaStream(mediaStreams, videoRequest.VideoStreamIndex, MediaStreamType.Video);
                state.SubtitleStream = GetMediaStream(mediaStreams, videoRequest.SubtitleStreamIndex, MediaStreamType.Subtitle, false);
                state.AudioStream = GetMediaStream(mediaStreams, videoRequest.AudioStreamIndex, MediaStreamType.Audio);

                if (state.SubtitleStream != null && !state.SubtitleStream.IsExternal)
                {
                    state.InternalSubtitleStreamOffset = mediaStreams.Where(i => i.Type == MediaStreamType.Subtitle && !i.IsExternal).ToList().IndexOf(state.SubtitleStream);
                }

                if (state.VideoStream != null && state.VideoStream.IsInterlaced)
                {
                    state.DeInterlace = true;
                }

                EnforceResolutionLimit(state, videoRequest);
            }
            else
            {
                state.AudioStream = GetMediaStream(mediaStreams, null, MediaStreamType.Audio, true);
            }

            state.MediaSource = mediaSource;
        }

        /// <summary>
        /// Gets the name of the output audio codec
        /// </summary>
        /// <param name="request">The request.</param>
        /// <returns>System.String.</returns>
        private string GetAudioCodec(EncodingJobOptions request)
        {
            var codec = request.AudioCodec;

            if (string.Equals(codec, "aac", StringComparison.OrdinalIgnoreCase))
            {
                return "aac -strict experimental";
            }
            if (string.Equals(codec, "mp3", StringComparison.OrdinalIgnoreCase))
            {
                return "libmp3lame";
            }
            if (string.Equals(codec, "vorbis", StringComparison.OrdinalIgnoreCase))
            {
                return "libvorbis";
            }
            if (string.Equals(codec, "wma", StringComparison.OrdinalIgnoreCase))
            {
                return "wmav2";
            }

            return (codec ?? string.Empty).ToLower();
        }

        internal static bool CanStreamCopyVideo(EncodingJobOptions request, MediaStream videoStream)
        {
            if (videoStream.IsInterlaced)
            {
                return false;
            }

            if (videoStream.IsAnamorphic ?? false)
            {
                return false;
            }

            // Can't stream copy if we're burning in subtitles
            if (request.SubtitleStreamIndex.HasValue)
            {
                if (request.SubtitleMethod == SubtitleDeliveryMethod.Encode)
                {
                    return false;
                }
            }

            // Source and target codecs must match
            if (!string.Equals(request.VideoCodec, videoStream.Codec, StringComparison.OrdinalIgnoreCase))
            {
                return false;
            }

            // If client is requesting a specific video profile, it must match the source
            if (!string.IsNullOrEmpty(request.Profile))
            {
                if (string.IsNullOrEmpty(videoStream.Profile))
                {
                    return false;
                }

                if (!string.Equals(request.Profile, videoStream.Profile, StringComparison.OrdinalIgnoreCase))
                {
                    var currentScore = GetVideoProfileScore(videoStream.Profile);
                    var requestedScore = GetVideoProfileScore(request.Profile);

                    if (currentScore == -1 || currentScore > requestedScore)
                    {
                        return false;
                    }
                }
            }

            // Video width must fall within requested value
            if (request.MaxWidth.HasValue)
            {
                if (!videoStream.Width.HasValue || videoStream.Width.Value > request.MaxWidth.Value)
                {
                    return false;
                }
            }

            // Video height must fall within requested value
            if (request.MaxHeight.HasValue)
            {
                if (!videoStream.Height.HasValue || videoStream.Height.Value > request.MaxHeight.Value)
                {
                    return false;
                }
            }

            // Video framerate must fall within requested value
            var requestedFramerate = request.MaxFramerate ?? request.Framerate;
            if (requestedFramerate.HasValue)
            {
                var videoFrameRate = videoStream.AverageFrameRate ?? videoStream.RealFrameRate;

                if (!videoFrameRate.HasValue || videoFrameRate.Value > requestedFramerate.Value)
                {
                    return false;
                }
            }

            // Video bitrate must fall within requested value
            if (request.VideoBitRate.HasValue)
            {
                if (!videoStream.BitRate.HasValue || videoStream.BitRate.Value > request.VideoBitRate.Value)
                {
                    return false;
                }
            }

            if (request.MaxVideoBitDepth.HasValue)
            {
                if (videoStream.BitDepth.HasValue && videoStream.BitDepth.Value > request.MaxVideoBitDepth.Value)
                {
                    return false;
                }
            }

            if (request.MaxRefFrames.HasValue)
            {
                if (videoStream.RefFrames.HasValue && videoStream.RefFrames.Value > request.MaxRefFrames.Value)
                {
                    return false;
                }
//.........这里部分代码省略.........

        /// <summary>
        /// Gets the fast seek command line parameter.
        /// </summary>
        /// <param name="options">The options.</param>
        /// <returns>System.String.</returns>
        /// <value>The fast seek command line parameter.</value>
        protected string GetFastSeekCommandLineParameter(EncodingJobOptions options)
        {
            var time = options.StartTimeTicks;

            if (time.HasValue && time.Value > 0)
            {
                return string.Format("-ss {0}", MediaEncoder.GetTimeParameter(time.Value));
            }

            return string.Empty;
        }

 private void AttachMediaStreamInfo(EncodingJob state,
   MediaSourceInfo mediaSource,
   EncodingJobOptions videoRequest)
 {
     EncodingJobFactory.AttachMediaStreamInfo(state, mediaSource, videoRequest);
 }

        /// <summary>
        /// Gets the fast seek command line parameter.
        /// </summary>
        /// <param name="request">The request.</param>
        /// <returns>System.String.</returns>
        /// <value>The fast seek command line parameter.</value>
        protected string GetFastSeekCommandLineParameter(EncodingJobOptions request)
        {
            var time = request.StartTimeTicks ?? 0;

            if (time > 0)
            {
                return string.Format("-ss {0}", MediaEncoder.GetTimeParameter(time));
            }

            return string.Empty;
        }

 protected virtual string GetWorkingDirectory(EncodingJobOptions options)
 {
     return null;
 }

        /// <summary>
        /// Gets the number of audio channels to specify on the command line
        /// </summary>
        /// <param name="request">The request.</param>
        /// <param name="audioStream">The audio stream.</param>
        /// <param name="outputAudioCodec">The output audio codec.</param>
        /// <returns>System.Nullable{System.Int32}.</returns>
        private int? GetNumAudioChannelsParam(EncodingJobOptions request, MediaStream audioStream, string outputAudioCodec)
        {
            if (audioStream != null)
            {
                var codec = outputAudioCodec ?? string.Empty;

                if (audioStream.Channels > 2 && codec.IndexOf("wma", StringComparison.OrdinalIgnoreCase) != -1)
                {
                    // wmav2 currently only supports two channel output
                    return 2;
                }
            }

            if (request.MaxAudioChannels.HasValue)
            {
                if (audioStream != null && audioStream.Channels.HasValue)
                {
                    return Math.Min(request.MaxAudioChannels.Value, audioStream.Channels.Value);
                }

                // If we don't have any media info then limit it to 5 to prevent encoding errors due to asking for too many channels
                return Math.Min(request.MaxAudioChannels.Value, 5);
            }

            return request.AudioChannels;
        }

        public async Task<EncodingJob> CreateJob(EncodingJobOptions options, bool isVideoRequest, IProgress<double> progress, CancellationToken cancellationToken)
        {
            var request = options;

            if (string.IsNullOrEmpty(request.AudioCodec))
            {
                request.AudioCodec = InferAudioCodec(request.OutputContainer);
            } 
            
            var state = new EncodingJob(_logger, _liveTvManager)
            {
                Options = options,
                IsVideoRequest = isVideoRequest,
                Progress = progress
            };

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

            var item = _libraryManager.GetItemById(request.ItemId);

            List<MediaStream> mediaStreams = null;

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

            if (item is ILiveTvRecording)
            {
                var recording = await _liveTvManager.GetInternalRecording(request.ItemId, 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;
                }

                state.RunTimeTicks = recording.RunTimeTicks;
                state.DeInterlace = true;
                state.OutputAudioSync = "1000";
                state.InputVideoSync = "-1";
                state.InputAudioSync = "1";
                state.InputContainer = recording.Container;
                state.ReadInputAtNativeFramerate = source.ReadAtNativeFramerate;
            }
            else if (item is LiveTvChannel)
            {
                var channel = _liveTvManager.GetInternalChannel(request.ItemId);

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

                state.DeInterlace = true;

                // Just to prevent this from being null and causing other methods to fail
                state.MediaPath = string.Empty;
            }
            else if (item is IChannelMediaItem)
            {
                var mediaSource = await GetChannelMediaInfo(request.ItemId, request.MediaSourceId, cancellationToken).ConfigureAwait(false);
                state.IsInputVideo = string.Equals(item.MediaType, MediaType.Video, StringComparison.OrdinalIgnoreCase);
                state.InputProtocol = mediaSource.Protocol;
                state.MediaPath = mediaSource.Path;
                state.RunTimeTicks = item.RunTimeTicks;
                state.RemoteHttpHeaders = mediaSource.RequiredHttpHeaders;
                state.InputBitrate = mediaSource.Bitrate;
                state.InputFileSize = mediaSource.Size;
                state.ReadInputAtNativeFramerate = mediaSource.ReadAtNativeFramerate;
                mediaStreams = mediaSource.MediaStreams;
            }
            else
            {
                var hasMediaSources = (IHasMediaSources)item;
                var mediaSource = string.IsNullOrEmpty(request.MediaSourceId)
                    ? hasMediaSources.GetMediaSources(false).First()
                    : hasMediaSources.GetMediaSources(false).First(i => string.Equals(i.Id, request.MediaSourceId));

                mediaStreams = mediaSource.MediaStreams;
//.........这里部分代码省略.........

        internal static void AttachMediaStreamInfo(EncodingJob state,
            List<MediaStream> mediaStreams,
            EncodingJobOptions videoRequest)
        {
            if (videoRequest != null)
            {
                if (string.IsNullOrEmpty(videoRequest.VideoCodec))
                {
                    videoRequest.VideoCodec = InferVideoCodec(videoRequest.OutputContainer);
                }

                state.VideoStream = GetMediaStream(mediaStreams, videoRequest.VideoStreamIndex, MediaStreamType.Video);
                state.SubtitleStream = GetMediaStream(mediaStreams, videoRequest.SubtitleStreamIndex, MediaStreamType.Subtitle, false);
                state.AudioStream = GetMediaStream(mediaStreams, videoRequest.AudioStreamIndex, MediaStreamType.Audio);

                if (state.SubtitleStream != null && !state.SubtitleStream.IsExternal)
                {
                    state.InternalSubtitleStreamOffset = mediaStreams.Where(i => i.Type == MediaStreamType.Subtitle && !i.IsExternal).ToList().IndexOf(state.SubtitleStream);
                }

                if (state.VideoStream != null && state.VideoStream.IsInterlaced)
                {
                    state.DeInterlace = true;
                }

                EnforceResolutionLimit(state, videoRequest);
            }
            else
            {
                state.AudioStream = GetMediaStream(mediaStreams, null, MediaStreamType.Audio, true);
            }

            state.AllMediaStreams = mediaStreams;
        }

        private int? GetVideoBitrateParamValue(EncodingJobOptions request, MediaStream videoStream)
        {
            var bitrate = request.VideoBitRate;

            if (videoStream != null)
            {
                var isUpscaling = request.Height.HasValue && videoStream.Height.HasValue &&
                                   request.Height.Value > videoStream.Height.Value;

                if (request.Width.HasValue && videoStream.Width.HasValue &&
                    request.Width.Value > videoStream.Width.Value)
                {
                    isUpscaling = true;
                }

                // Don't allow bitrate increases unless upscaling
                if (!isUpscaling)
                {
                    if (bitrate.HasValue && videoStream.BitRate.HasValue)
                    {
                        bitrate = Math.Min(bitrate.Value, videoStream.BitRate.Value);
                    }
                }
            }

            return bitrate;
        }

        public async Task<EncodingJob> Start(EncodingJobOptions options,
            IProgress<double> progress,
            CancellationToken cancellationToken)
        {
            var encodingJob = await new EncodingJobFactory(Logger, LibraryManager, MediaSourceManager, ConfigurationManager)
                .CreateJob(options, IsVideoEncoder, progress, cancellationToken).ConfigureAwait(false);

            encodingJob.OutputFilePath = GetOutputFilePath(encodingJob);
            FileSystem.CreateDirectory(Path.GetDirectoryName(encodingJob.OutputFilePath));

            encodingJob.ReadInputAtNativeFramerate = options.ReadInputAtNativeFramerate;

            await AcquireResources(encodingJob, cancellationToken).ConfigureAwait(false);

            var commandLineArgs = GetCommandLineArguments(encodingJob);

            if (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
            };

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

            OnTranscodeBeginning(encodingJob);

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

            var logFilePath = Path.Combine(ConfigurationManager.CommonApplicationPaths.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.
            encodingJob.LogFileStream = FileSystem.GetFileStream(logFilePath, FileMode.Create, FileAccess.Write, FileShare.Read, true);

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

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

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

                OnTranscodeFailedToStart(encodingJob.OutputFilePath, encodingJob);

                throw;
            }

            cancellationToken.Register(() => Cancel(process, encodingJob));
            
            // 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
            new JobLogger(Logger).StartStreamingLog(encodingJob, process.StandardError.BaseStream, encodingJob.LogFileStream);

            // Wait for the file to exist before proceeeding
			while (!FileSystem.FileExists(encodingJob.OutputFilePath) && !encodingJob.HasExited)
            {
                await Task.Delay(100, cancellationToken).ConfigureAwait(false);
            }

            return encodingJob;
        }

        private int? GetAudioBitrateParam(EncodingJobOptions request, MediaStream audioStream)
        {
            if (request.AudioBitRate.HasValue)
            {
                // Make sure we don't request a bitrate higher than the source
                var currentBitrate = audioStream == null ? request.AudioBitRate.Value : audioStream.BitRate ?? request.AudioBitRate.Value;

                return request.AudioBitRate.Value;
                //return Math.Min(currentBitrate, request.AudioBitRate.Value);
            }

            return null;
        }

        public async Task<string> EncodeVideo(EncodingJobOptions options,
            IProgress<double> progress,
            CancellationToken cancellationToken)
        {
            var job = await new VideoEncoder(this,
                _logger,
                ConfigurationManager,
                FileSystem,
                LiveTvManager,
                IsoManager,
                LibraryManager,
                ChannelManager,
                SessionManager,
                SubtitleEncoder())
                .Start(options, progress, cancellationToken).ConfigureAwait(false);

            await job.TaskCompletionSource.Task.ConfigureAwait(false);

            return job.OutputFilePath;
        }

        /// <summary>
        /// Gets the name of the output video codec
        /// </summary>
        /// <param name="request">The request.</param>
        /// <returns>System.String.</returns>
        private string GetVideoCodec(EncodingJobOptions request)
        {
            var codec = request.VideoCodec;

            if (string.Equals(codec, "h264", StringComparison.OrdinalIgnoreCase))
            {
                return "libx264";
            }
            if (string.Equals(codec, "h265", StringComparison.OrdinalIgnoreCase))
            {
                return "libx265";
            }
            if (string.Equals(codec, "vpx", StringComparison.OrdinalIgnoreCase))
            {
                return "libvpx";
            }
            if (string.Equals(codec, "wmv", StringComparison.OrdinalIgnoreCase))
            {
                return "wmv2";
            }
            if (string.Equals(codec, "theora", StringComparison.OrdinalIgnoreCase))
            {
                return "libtheora";
            }

            return (codec ?? string.Empty).ToLower();
        }

        internal static void TryStreamCopy(EncodingJob state,
            EncodingJobOptions videoRequest)
        {
            if (state.IsVideoRequest)
            {
                if (state.VideoStream != null && CanStreamCopyVideo(videoRequest, state.VideoStream))
                {
                    state.OutputVideoCodec = "copy";
                }

                if (state.AudioStream != null && CanStreamCopyAudio(videoRequest, state.AudioStream, state.SupportedAudioCodecs))
                {
                    state.OutputAudioCodec = "copy";
                }
            }
        }