jellyfin/MediaBrowser.Api/Playback/Hls/DynamicHlsService.cs

using System;
using System.Collections.Generic;
using System.Globalization;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using MediaBrowser.Common.Net;
using MediaBrowser.Controller.Configuration;
using MediaBrowser.Controller.Devices;
using MediaBrowser.Controller.Dlna;
using MediaBrowser.Controller.Library;
using MediaBrowser.Controller.MediaEncoding;
using MediaBrowser.Controller.Net;
using MediaBrowser.Model.Configuration;
using MediaBrowser.Model.Dlna;
using MediaBrowser.Model.Entities;
using MediaBrowser.Model.IO;
using MediaBrowser.Model.Serialization;
using MediaBrowser.Model.Services;
using Microsoft.Extensions.Logging;
using MimeTypes = MediaBrowser.Model.Net.MimeTypes;

namespace MediaBrowser.Api.Playback.Hls
{
    /// <summary>
    /// Options is needed for chromecast. Threw Head in there since it's related
    /// </summary>
    [Route("/Videos/{Id}/master.m3u8", "GET", Summary = "Gets a video stream using HTTP live streaming.")]
    [Route("/Videos/{Id}/master.m3u8", "HEAD", Summary = "Gets a video stream using HTTP live streaming.")]
    public class GetMasterHlsVideoPlaylist : VideoStreamRequest, IMasterHlsRequest
    {
        public bool EnableAdaptiveBitrateStreaming { get; set; }

        public GetMasterHlsVideoPlaylist()
        {
            EnableAdaptiveBitrateStreaming = true;
        }
    }

    [Route("/Audio/{Id}/master.m3u8", "GET", Summary = "Gets an audio stream using HTTP live streaming.")]
    [Route("/Audio/{Id}/master.m3u8", "HEAD", Summary = "Gets an audio stream using HTTP live streaming.")]
    public class GetMasterHlsAudioPlaylist : StreamRequest, IMasterHlsRequest
    {
        public bool EnableAdaptiveBitrateStreaming { get; set; }

        public GetMasterHlsAudioPlaylist()
        {
            EnableAdaptiveBitrateStreaming = true;
        }
    }

    public interface IMasterHlsRequest
    {
        bool EnableAdaptiveBitrateStreaming { get; set; }
    }

    [Route("/Videos/{Id}/main.m3u8", "GET", Summary = "Gets a video stream using HTTP live streaming.")]
    public class GetVariantHlsVideoPlaylist : VideoStreamRequest
    {
    }

    [Route("/Audio/{Id}/main.m3u8", "GET", Summary = "Gets an audio stream using HTTP live streaming.")]
    public class GetVariantHlsAudioPlaylist : StreamRequest
    {
    }

    [Route("/Videos/{Id}/hls1/{PlaylistId}/{SegmentId}.{SegmentContainer}", "GET")]
    public class GetHlsVideoSegment : VideoStreamRequest
    {
        public string PlaylistId { get; set; }

        /// <summary>
        /// Gets or sets the segment id.
        /// </summary>
        /// <value>The segment id.</value>
        public string SegmentId { get; set; }
    }

    [Route("/Audio/{Id}/hls1/{PlaylistId}/{SegmentId}.{SegmentContainer}", "GET")]
    public class GetHlsAudioSegment : StreamRequest
    {
        public string PlaylistId { get; set; }

        /// <summary>
        /// Gets or sets the segment id.
        /// </summary>
        /// <value>The segment id.</value>
        public string SegmentId { get; set; }
    }

    [Authenticated]
    public class DynamicHlsService : BaseHlsService
    {
        public DynamicHlsService(
            ILogger logger,
            IServerConfigurationManager serverConfigurationManager,
            IHttpResultFactory httpResultFactory,
            IUserManager userManager,
            ILibraryManager libraryManager,
            IIsoManager isoManager,
            IMediaEncoder mediaEncoder,
            IFileSystem fileSystem,
            IDlnaManager dlnaManager,
            IDeviceManager deviceManager,
            IMediaSourceManager mediaSourceManager,
            IJsonSerializer jsonSerializer,
            IAuthorizationContext authorizationContext,
            INetworkManager networkManager,
            EncodingHelper encodingHelper)
            : base(
                logger,
                serverConfigurationManager,
                httpResultFactory,
                userManager,
                libraryManager,
                isoManager,
                mediaEncoder,
                fileSystem,
                dlnaManager,
                deviceManager,
                mediaSourceManager,
                jsonSerializer,
                authorizationContext,
                encodingHelper)
        {
            NetworkManager = networkManager;
        }

        protected INetworkManager NetworkManager { get; private set; }

        public Task<object> Get(GetMasterHlsVideoPlaylist request)
        {
            return GetMasterPlaylistInternal(request, "GET");
        }

        public Task<object> Head(GetMasterHlsVideoPlaylist request)
        {
            return GetMasterPlaylistInternal(request, "HEAD");
        }

        public Task<object> Get(GetMasterHlsAudioPlaylist request)
        {
            return GetMasterPlaylistInternal(request, "GET");
        }

        public Task<object> Head(GetMasterHlsAudioPlaylist request)
        {
            return GetMasterPlaylistInternal(request, "HEAD");
        }

        public Task<object> Get(GetVariantHlsVideoPlaylist request)
        {
            return GetVariantPlaylistInternal(request, true, "main");
        }

        public Task<object> Get(GetVariantHlsAudioPlaylist request)
        {
            return GetVariantPlaylistInternal(request, false, "main");
        }

        public Task<object> Get(GetHlsVideoSegment request)
        {
            return GetDynamicSegment(request, request.SegmentId);
        }

        public Task<object> Get(GetHlsAudioSegment request)
        {
            return GetDynamicSegment(request, request.SegmentId);
        }

        private async Task<object> GetDynamicSegment(StreamRequest request, string segmentId)
        {
            if ((request.StartTimeTicks ?? 0) > 0)
            {
                throw new ArgumentException("StartTimeTicks is not allowed.");
            }

            var cancellationTokenSource = new CancellationTokenSource();
            var cancellationToken = cancellationTokenSource.Token;

            var requestedIndex = int.Parse(segmentId, NumberStyles.Integer, CultureInfo.InvariantCulture);

            var state = await GetState(request, cancellationToken).ConfigureAwait(false);

            var playlistPath = Path.ChangeExtension(state.OutputFilePath, ".m3u8");

            var segmentPath = GetSegmentPath(state, playlistPath, requestedIndex);

            var segmentExtension = GetSegmentFileExtension(state.Request);

            TranscodingJob job = null;

            if (File.Exists(segmentPath))
            {
                job = ApiEntryPoint.Instance.OnTranscodeBeginRequest(playlistPath, TranscodingJobType);
                Logger.LogDebug("returning {0} [it exists, try 1]", segmentPath);
                return await GetSegmentResult(state, playlistPath, segmentPath, segmentExtension, requestedIndex, job, cancellationToken).ConfigureAwait(false);
            }

            var transcodingLock = ApiEntryPoint.Instance.GetTranscodingLock(playlistPath);
            await transcodingLock.WaitAsync(cancellationTokenSource.Token).ConfigureAwait(false);
            var released = false;
            var startTranscoding = false;

            try
            {
                if (File.Exists(segmentPath))
                {
                    job = ApiEntryPoint.Instance.OnTranscodeBeginRequest(playlistPath, TranscodingJobType);
                    transcodingLock.Release();
                    released = true;
                    Logger.LogDebug("returning {0} [it exists, try 2]", segmentPath);
                    return await GetSegmentResult(state, playlistPath, segmentPath, segmentExtension, requestedIndex, job, cancellationToken).ConfigureAwait(false);
                }
                else
                {
                    var currentTranscodingIndex = GetCurrentTranscodingIndex(playlistPath, segmentExtension);
                    var segmentGapRequiringTranscodingChange = 24 / state.SegmentLength;

                    if (currentTranscodingIndex == null)
                    {
                        Logger.LogDebug("Starting transcoding because currentTranscodingIndex=null");
                        startTranscoding = true;
                    }
                    else if (requestedIndex < currentTranscodingIndex.Value)
                    {
                        Logger.LogDebug("Starting transcoding because requestedIndex={0} and currentTranscodingIndex={1}", requestedIndex, currentTranscodingIndex);
                        startTranscoding = true;
                    }
                    else if (requestedIndex - currentTranscodingIndex.Value > segmentGapRequiringTranscodingChange)
                    {
                        Logger.LogDebug("Starting transcoding because segmentGap is {0} and max allowed gap is {1}. requestedIndex={2}", requestedIndex - currentTranscodingIndex.Value, segmentGapRequiringTranscodingChange, requestedIndex);
                        startTranscoding = true;
                    }
                    if (startTranscoding)
                    {
                        // If the playlist doesn't already exist, startup ffmpeg
                        try
                        {
                            await ApiEntryPoint.Instance.KillTranscodingJobs(request.DeviceId, request.PlaySessionId, p => false);

                            if (currentTranscodingIndex.HasValue)
                            {
                                DeleteLastFile(playlistPath, segmentExtension, 0);
                            }

                            request.StartTimeTicks = GetStartPositionTicks(state, requestedIndex);

                            state.WaitForPath = segmentPath;
                            job = await StartFfMpeg(state, playlistPath, cancellationTokenSource).ConfigureAwait(false);
                        }
                        catch
                        {
                            state.Dispose();
                            throw;
                        }

                        //await WaitForMinimumSegmentCount(playlistPath, 1, cancellationTokenSource.Token).ConfigureAwait(false);
                    }
                    else
                    {
                        job = ApiEntryPoint.Instance.OnTranscodeBeginRequest(playlistPath, TranscodingJobType);
                        if (job.TranscodingThrottler != null)
                        {
                            await job.TranscodingThrottler.UnpauseTranscoding();
                        }
                    }
                }
            }
            finally
            {
                if (!released)
                {
                    transcodingLock.Release();
                }
            }

            //Logger.LogInformation("waiting for {0}", segmentPath);
            //while (!File.Exists(segmentPath))
            //{
            //    await Task.Delay(50, cancellationToken).ConfigureAwait(false);
            //}

            Logger.LogDebug("returning {0} [general case]", segmentPath);
            job = job ?? ApiEntryPoint.Instance.OnTranscodeBeginRequest(playlistPath, TranscodingJobType);
            return await GetSegmentResult(state, playlistPath, segmentPath, segmentExtension, requestedIndex, job, cancellationToken).ConfigureAwait(false);
        }

        private const int BufferSize = 81920;

        private long GetStartPositionTicks(StreamState state, int requestedIndex)
        {
            double startSeconds = 0;
            var lengths = GetSegmentLengths(state);

            if (requestedIndex >= lengths.Length)
            {
                var msg = string.Format("Invalid segment index requested: {0} - Segment count: {1}", requestedIndex, lengths.Length);
                throw new ArgumentException(msg);
            }

            for (var i = 0; i < requestedIndex; i++)
            {
                startSeconds += lengths[i];
            }

            var position = TimeSpan.FromSeconds(startSeconds).Ticks;
            return position;
        }

        private long GetEndPositionTicks(StreamState state, int requestedIndex)
        {
            double startSeconds = 0;
            var lengths = GetSegmentLengths(state);

            if (requestedIndex >= lengths.Length)
            {
                var msg = string.Format("Invalid segment index requested: {0} - Segment count: {1}", requestedIndex, lengths.Length);
                throw new ArgumentException(msg);
            }

            for (var i = 0; i <= requestedIndex; i++)
            {
                startSeconds += lengths[i];
            }

            var position = TimeSpan.FromSeconds(startSeconds).Ticks;
            return position;
        }

        private double[] GetSegmentLengths(StreamState state)
        {
            var result = new List<double>();

            var ticks = state.RunTimeTicks ?? 0;

            var segmentLengthTicks = TimeSpan.FromSeconds(state.SegmentLength).Ticks;

            while (ticks > 0)
            {
                var length = ticks >= segmentLengthTicks ? segmentLengthTicks : ticks;

                result.Add(TimeSpan.FromTicks(length).TotalSeconds);

                ticks -= length;
            }

            return result.ToArray();
        }

        public int? GetCurrentTranscodingIndex(string playlist, string segmentExtension)
        {
            var job = ApiEntryPoint.Instance.GetTranscodingJob(playlist, TranscodingJobType);

            if (job == null || job.HasExited)
            {
                return null;
            }

            var file = GetLastTranscodingFile(playlist, segmentExtension, FileSystem);

            if (file == null)
            {
                return null;
            }

            var playlistFilename = Path.GetFileNameWithoutExtension(playlist);

            var indexString = Path.GetFileNameWithoutExtension(file.Name).Substring(playlistFilename.Length);

            return int.Parse(indexString, NumberStyles.Integer, CultureInfo.InvariantCulture);
        }

        private void DeleteLastFile(string playlistPath, string segmentExtension, int retryCount)
        {
            var file = GetLastTranscodingFile(playlistPath, segmentExtension, FileSystem);

            if (file != null)
            {
                DeleteFile(file.FullName, retryCount);
            }
        }

        private void DeleteFile(string path, int retryCount)
        {
            if (retryCount >= 5)
            {
                return;
            }

            Logger.LogDebug("Deleting partial HLS file {path}", path);

            try
            {
                FileSystem.DeleteFile(path);
            }
            catch (IOException ex)
            {
                Logger.LogError(ex, "Error deleting partial stream file(s) {path}", path);

                var task = Task.Delay(100);
                Task.WaitAll(task);
                DeleteFile(path, retryCount + 1);
            }
            catch (Exception ex)
            {
                Logger.LogError(ex, "Error deleting partial stream file(s) {path}", path);
            }
        }

        private static FileSystemMetadata GetLastTranscodingFile(string playlist, string segmentExtension, IFileSystem fileSystem)
        {
            var folder = Path.GetDirectoryName(playlist);

            var filePrefix = Path.GetFileNameWithoutExtension(playlist) ?? string.Empty;

            try
            {
                return fileSystem.GetFiles(folder, new[] { segmentExtension }, true, false)
                    .Where(i => Path.GetFileNameWithoutExtension(i.Name).StartsWith(filePrefix, StringComparison.OrdinalIgnoreCase))
                    .OrderByDescending(fileSystem.GetLastWriteTimeUtc)
                    .FirstOrDefault();
            }
            catch (IOException)
            {
                return null;
            }
        }

        protected override int GetStartNumber(StreamState state)
        {
            return GetStartNumber(state.VideoRequest);
        }

        private int GetStartNumber(VideoStreamRequest request)
        {
            var segmentId = "0";

            if (request is GetHlsVideoSegment segmentRequest)
            {
                segmentId = segmentRequest.SegmentId;
            }

            return int.Parse(segmentId, NumberStyles.Integer, CultureInfo.InvariantCulture);
        }

        private string GetSegmentPath(StreamState state, string playlist, int index)
        {
            var folder = Path.GetDirectoryName(playlist);

            var filename = Path.GetFileNameWithoutExtension(playlist);

            return Path.Combine(folder, filename + index.ToString(CultureInfo.InvariantCulture) + GetSegmentFileExtension(state.Request));
        }

        private async Task<object> GetSegmentResult(StreamState state,
            string playlistPath,
            string segmentPath,
            string segmentExtension,
            int segmentIndex,
            TranscodingJob transcodingJob,
            CancellationToken cancellationToken)
        {
            var segmentExists = File.Exists(segmentPath);
            if (segmentExists)
            {
                if (transcodingJob != null && transcodingJob.HasExited)
                {
                    // Transcoding job is over, so assume all existing files are ready
                    Logger.LogDebug("serving up {0} as transcode is over", segmentPath);
                    return await GetSegmentResult(state, segmentPath, segmentIndex, transcodingJob).ConfigureAwait(false);
                }

                var currentTranscodingIndex = GetCurrentTranscodingIndex(playlistPath, segmentExtension);

                // If requested segment is less than transcoding position, we can't transcode backwards, so assume it's ready
                if (segmentIndex < currentTranscodingIndex)
                {
                    Logger.LogDebug("serving up {0} as transcode index {1} is past requested point {2}", segmentPath, currentTranscodingIndex, segmentIndex);
                    return await GetSegmentResult(state, segmentPath, segmentIndex, transcodingJob).ConfigureAwait(false);
                }
            }

            var nextSegmentPath = GetSegmentPath(state, playlistPath, segmentIndex + 1);
            if (transcodingJob != null)
            {
                while (!cancellationToken.IsCancellationRequested && !transcodingJob.HasExited)
                {
                    // To be considered ready, the segment file has to exist AND
                    // either the transcoding job should be done or next segment should also exist
                    if (segmentExists)
                    {
                        if (transcodingJob.HasExited || File.Exists(nextSegmentPath))
                        {
                            Logger.LogDebug("serving up {0} as it deemed ready", segmentPath);
                            return await GetSegmentResult(state, segmentPath, segmentIndex, transcodingJob).ConfigureAwait(false);
                        }
                    }
                    else
                    {
                        segmentExists = File.Exists(segmentPath);
                        if (segmentExists)
                        {
                            continue; // avoid unnecessary waiting if segment just became available
                        }
                    }

                    await Task.Delay(100, cancellationToken).ConfigureAwait(false);
                }

                if (!File.Exists(segmentPath))
                {
                    Logger.LogWarning("cannot serve {0} as transcoding quit before we got there", segmentPath);
                }
                else
                {
                    Logger.LogDebug("serving {0} as it's on disk and transcoding stopped", segmentPath);
                }
                cancellationToken.ThrowIfCancellationRequested();
            }
            else
            {
                Logger.LogWarning("cannot serve {0} as it doesn't exist and no transcode is running", segmentPath);
            }

            return await GetSegmentResult(state, segmentPath, segmentIndex, transcodingJob).ConfigureAwait(false);
        }

        private Task<object> GetSegmentResult(StreamState state, string segmentPath, int index, TranscodingJob transcodingJob)
        {
            var segmentEndingPositionTicks = GetEndPositionTicks(state, index);

            return ResultFactory.GetStaticFileResult(Request, new StaticFileResultOptions
            {
                Path = segmentPath,
                FileShare = FileShare.ReadWrite,
                OnComplete = () =>
                {
                    Logger.LogDebug("finished serving {0}", segmentPath);
                    if (transcodingJob != null)
                    {
                        transcodingJob.DownloadPositionTicks = Math.Max(transcodingJob.DownloadPositionTicks ?? segmentEndingPositionTicks, segmentEndingPositionTicks);
                        ApiEntryPoint.Instance.OnTranscodeEndRequest(transcodingJob);
                    }
                }
            });
        }

        private async Task<object> GetMasterPlaylistInternal(StreamRequest request, string method)
        {
            var state = await GetState(request, CancellationToken.None).ConfigureAwait(false);

            if (string.IsNullOrEmpty(request.MediaSourceId))
            {
                throw new ArgumentException("MediaSourceId is required");
            }

            var playlistText = string.Empty;

            if (string.Equals(method, "GET", StringComparison.OrdinalIgnoreCase))
            {
                var audioBitrate = state.OutputAudioBitrate ?? 0;
                var videoBitrate = state.OutputVideoBitrate ?? 0;

                playlistText = GetMasterPlaylistFileText(state, videoBitrate + audioBitrate);
            }

            return ResultFactory.GetResult(playlistText, MimeTypes.GetMimeType("playlist.m3u8"), new Dictionary<string, string>());
        }

        private string GetMasterPlaylistFileText(StreamState state, int totalBitrate)
        {
            var builder = new StringBuilder();

            builder.AppendLine("#EXTM3U");

            var isLiveStream = state.IsSegmentedLiveStream;

            var queryStringIndex = Request.RawUrl.IndexOf('?');
            var queryString = queryStringIndex == -1 ? string.Empty : Request.RawUrl.Substring(queryStringIndex);

            // from universal audio service
            if (queryString.IndexOf("SegmentContainer", StringComparison.OrdinalIgnoreCase) == -1 && !string.IsNullOrWhiteSpace(state.Request.SegmentContainer))
            {
                queryString += "&SegmentContainer=" + state.Request.SegmentContainer;
            }
            // from universal audio service
            if (!string.IsNullOrWhiteSpace(state.Request.TranscodeReasons) && queryString.IndexOf("TranscodeReasons=", StringComparison.OrdinalIgnoreCase) == -1)
            {
                queryString += "&TranscodeReasons=" + state.Request.TranscodeReasons;
            }

            // Main stream
            var playlistUrl = isLiveStream ? "live.m3u8" : "main.m3u8";

            playlistUrl += queryString;

            var request = state.Request;

            var subtitleStreams = state.MediaSource
                .MediaStreams
                .Where(i => i.IsTextSubtitleStream)
                .ToList();

            var subtitleGroup = subtitleStreams.Count > 0 &&
                request is GetMasterHlsVideoPlaylist &&
                (state.SubtitleDeliveryMethod == SubtitleDeliveryMethod.Hls || state.VideoRequest.EnableSubtitlesInManifest) ?
                "subs" :
                null;

            // If we're burning in subtitles then don't add additional subs to the manifest
            if (state.SubtitleStream != null && state.SubtitleDeliveryMethod == SubtitleDeliveryMethod.Encode)
            {
                subtitleGroup = null;
            }

            if (!string.IsNullOrWhiteSpace(subtitleGroup))
            {
                AddSubtitles(state, subtitleStreams, builder);
            }

            AppendPlaylist(builder, state, playlistUrl, totalBitrate, subtitleGroup);

            if (EnableAdaptiveBitrateStreaming(state, isLiveStream))
            {
                var requestedVideoBitrate = state.VideoRequest == null ? 0 : state.VideoRequest.VideoBitRate ?? 0;

                // By default, vary by just 200k
                var variation = GetBitrateVariation(totalBitrate);

                var newBitrate = totalBitrate - variation;
                var variantUrl = ReplaceBitrate(playlistUrl, requestedVideoBitrate, requestedVideoBitrate - variation);
                AppendPlaylist(builder, state, variantUrl, newBitrate, subtitleGroup);

                variation *= 2;
                newBitrate = totalBitrate - variation;
                variantUrl = ReplaceBitrate(playlistUrl, requestedVideoBitrate, requestedVideoBitrate - variation);
                AppendPlaylist(builder, state, variantUrl, newBitrate, subtitleGroup);
            }

            return builder.ToString();
        }

        private string ReplaceBitrate(string url, int oldValue, int newValue)
        {
            return url.Replace(
                "videobitrate=" + oldValue.ToString(CultureInfo.InvariantCulture),
                "videobitrate=" + newValue.ToString(CultureInfo.InvariantCulture),
                StringComparison.OrdinalIgnoreCase);
        }

        private void AddSubtitles(StreamState state, IEnumerable<MediaStream> subtitles, StringBuilder builder)
        {
            var selectedIndex = state.SubtitleStream == null || state.SubtitleDeliveryMethod != SubtitleDeliveryMethod.Hls ? (int?)null : state.SubtitleStream.Index;

            foreach (var stream in subtitles)
            {
                const string format = "#EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID=\"subs\",NAME=\"{0}\",DEFAULT={1},FORCED={2},AUTOSELECT=YES,URI=\"{3}\",LANGUAGE=\"{4}\"";

                var name = stream.DisplayTitle;

                var isDefault = selectedIndex.HasValue && selectedIndex.Value == stream.Index;
                var isForced = stream.IsForced;

                var url = string.Format("{0}/Subtitles/{1}/subtitles.m3u8?SegmentLength={2}&api_key={3}",
                    state.Request.MediaSourceId,
                    stream.Index.ToString(CultureInfo.InvariantCulture),
                    30.ToString(CultureInfo.InvariantCulture),
                    AuthorizationContext.GetAuthorizationInfo(Request).Token);

                var line = string.Format(format,
                    name,
                    isDefault ? "YES" : "NO",
                    isForced ? "YES" : "NO",
                    url,
                    stream.Language ?? "Unknown");

                builder.AppendLine(line);
            }
        }

        private bool EnableAdaptiveBitrateStreaming(StreamState state, bool isLiveStream)
        {
            // Within the local network this will likely do more harm than good.
            if (Request.IsLocal || NetworkManager.IsInLocalNetwork(Request.RemoteIp))
            {
                return false;
            }

            if (state.Request is IMasterHlsRequest request && !request.EnableAdaptiveBitrateStreaming)
            {
                return false;
            }

            if (isLiveStream || string.IsNullOrWhiteSpace(state.MediaPath))
            {
                // Opening live streams is so slow it's not even worth it
                return false;
            }

            if (string.Equals(state.OutputVideoCodec, "copy", StringComparison.OrdinalIgnoreCase))
            {
                return false;
            }

            if (string.Equals(state.OutputAudioCodec, "copy", StringComparison.OrdinalIgnoreCase))
            {
                return false;
            }

            if (!state.IsOutputVideo)
            {
                return false;
            }

            // Having problems in android
            return false;
            //return state.VideoRequest.VideoBitRate.HasValue;
        }

        private void AppendPlaylist(StringBuilder builder, StreamState state, string url, int bitrate, string subtitleGroup)
        {
            var header = "#EXT-X-STREAM-INF:BANDWIDTH=" + bitrate.ToString(CultureInfo.InvariantCulture) + ",AVERAGE-BANDWIDTH=" + bitrate.ToString(CultureInfo.InvariantCulture);

            // tvos wants resolution, codecs, framerate
            //if (state.TargetFramerate.HasValue)
            //{
            //    header += string.Format(",FRAME-RATE=\"{0}\"", state.TargetFramerate.Value.ToString(CultureInfo.InvariantCulture));
            //}

            if (!string.IsNullOrWhiteSpace(subtitleGroup))
            {
                header += string.Format(",SUBTITLES=\"{0}\"", subtitleGroup);
            }

            builder.AppendLine(header);
            builder.AppendLine(url);
        }

        private int GetBitrateVariation(int bitrate)
        {
            // By default, vary by just 50k
            var variation = 50000;

            if (bitrate >= 10000000)
            {
                variation = 2000000;
            }
            else if (bitrate >= 5000000)
            {
                variation = 1500000;
            }
            else if (bitrate >= 3000000)
            {
                variation = 1000000;
            }
            else if (bitrate >= 2000000)
            {
                variation = 500000;
            }
            else if (bitrate >= 1000000)
            {
                variation = 300000;
            }
            else if (bitrate >= 600000)
            {
                variation = 200000;
            }
            else if (bitrate >= 400000)
            {
                variation = 100000;
            }

            return variation;
        }

        private async Task<object> GetVariantPlaylistInternal(StreamRequest request, bool isOutputVideo, string name)
        {
            var state = await GetState(request, CancellationToken.None).ConfigureAwait(false);

            var segmentLengths = GetSegmentLengths(state);

            var builder = new StringBuilder();

            builder.AppendLine("#EXTM3U");
            builder.AppendLine("#EXT-X-PLAYLIST-TYPE:VOD");
            builder.AppendLine("#EXT-X-VERSION:3");
            builder.AppendLine("#EXT-X-TARGETDURATION:" + Math.Ceiling(segmentLengths.Length > 0 ? segmentLengths.Max() : state.SegmentLength).ToString(CultureInfo.InvariantCulture));
            builder.AppendLine("#EXT-X-MEDIA-SEQUENCE:0");

            var queryStringIndex = Request.RawUrl.IndexOf('?');
            var queryString = queryStringIndex == -1 ? string.Empty : Request.RawUrl.Substring(queryStringIndex);

            //if ((Request.UserAgent ?? string.Empty).IndexOf("roku", StringComparison.OrdinalIgnoreCase) != -1)
            //{
            //    queryString = string.Empty;
            //}

            var index = 0;

            foreach (var length in segmentLengths)
            {
                builder.AppendLine("#EXTINF:" + length.ToString("0.0000", CultureInfo.InvariantCulture) + ", nodesc");

                builder.AppendLine(string.Format("hls1/{0}/{1}{2}{3}",

                    name,
                    index.ToString(CultureInfo.InvariantCulture),
                    GetSegmentFileExtension(request),
                    queryString));

                index++;
            }

            builder.AppendLine("#EXT-X-ENDLIST");

            var playlistText = builder.ToString();

            return ResultFactory.GetResult(playlistText, MimeTypes.GetMimeType("playlist.m3u8"), new Dictionary<string, string>());
        }

        protected override string GetAudioArguments(StreamState state, EncodingOptions encodingOptions)
        {
            var audioCodec = EncodingHelper.GetAudioEncoder(state);

            if (!state.IsOutputVideo)
            {
                if (string.Equals(audioCodec, "copy", StringComparison.OrdinalIgnoreCase))
                {
                    return "-acodec copy";
                }

                var audioTranscodeParams = new List<string>();

                audioTranscodeParams.Add("-acodec " + audioCodec);

                if (state.OutputAudioBitrate.HasValue)
                {
                    audioTranscodeParams.Add("-ab " + state.OutputAudioBitrate.Value.ToString(CultureInfo.InvariantCulture));
                }

                if (state.OutputAudioChannels.HasValue)
                {
                    audioTranscodeParams.Add("-ac " + state.OutputAudioChannels.Value.ToString(CultureInfo.InvariantCulture));
                }

                if (state.OutputAudioSampleRate.HasValue)
                {
                    audioTranscodeParams.Add("-ar " + state.OutputAudioSampleRate.Value.ToString(CultureInfo.InvariantCulture));
                }

                audioTranscodeParams.Add("-vn");
                return string.Join(" ", audioTranscodeParams.ToArray());
            }

            if (string.Equals(audioCodec, "copy", StringComparison.OrdinalIgnoreCase))
            {
                var videoCodec = EncodingHelper.GetVideoEncoder(state, encodingOptions);

                if (string.Equals(videoCodec, "copy", StringComparison.OrdinalIgnoreCase) && state.EnableBreakOnNonKeyFrames(videoCodec))
                {
                    return "-codec:a:0 copy -copypriorss:a:0 0";
                }

                return "-codec:a:0 copy";
            }

            var args = "-codec:a:0 " + audioCodec;

            var channels = state.OutputAudioChannels;

            if (channels.HasValue)
            {
                args += " -ac " + channels.Value;
            }

            var bitrate = state.OutputAudioBitrate;

            if (bitrate.HasValue)
            {
                args += " -ab " + bitrate.Value.ToString(CultureInfo.InvariantCulture);
            }

            if (state.OutputAudioSampleRate.HasValue)
            {
                args += " -ar " + state.OutputAudioSampleRate.Value.ToString(CultureInfo.InvariantCulture);
            }

            args += " " + EncodingHelper.GetAudioFilterParam(state, encodingOptions, true);

            return args;
        }

        protected override string GetVideoArguments(StreamState state, EncodingOptions encodingOptions)
        {
            if (!state.IsOutputVideo)
            {
                return string.Empty;
            }

            var codec = EncodingHelper.GetVideoEncoder(state, encodingOptions);

            var args = "-codec:v:0 " + codec;

            // if (state.EnableMpegtsM2TsMode)
            // {
            //     args += " -mpegts_m2ts_mode 1";
            // }

            // See if we can save come cpu cycles by avoiding encoding
            if (string.Equals(codec, "copy", StringComparison.OrdinalIgnoreCase))
            {
                if (state.VideoStream != null && !string.Equals(state.VideoStream.NalLengthSize, "0", StringComparison.OrdinalIgnoreCase))
                {
                    string bitStreamArgs = EncodingHelper.GetBitStreamArgs(state.VideoStream);
                    if (!string.IsNullOrEmpty(bitStreamArgs))
                    {
                        args += " " + bitStreamArgs;
                    }
                }

                //args += " -flags -global_header";
            }
            else
            {
                var gopArg = string.Empty;
                var keyFrameArg = string.Format(
                    CultureInfo.InvariantCulture,
                    " -force_key_frames:0 \"expr:gte(t,{0}+n_forced*{1})\"",
                    GetStartNumber(state) * state.SegmentLength,
                    state.SegmentLength);

                var framerate = state.VideoStream?.RealFrameRate;

                if (framerate != null && framerate.HasValue)
                {
                    // This is to make sure keyframe interval is limited to our segment,
                    // as forcing keyframes is not enough.
                    // Example: we encoded half of desired length, then codec detected
                    // scene cut and inserted a keyframe; next forced keyframe would
                    // be created outside of segment, which breaks seeking
                    // -sc_threshold 0 is used to prevent the hardware encoder from post processing to break the set keyframe
                    gopArg = string.Format(
                        CultureInfo.InvariantCulture,
                        " -g {0} -keyint_min {0} -sc_threshold 0",
                        Math.Ceiling(state.SegmentLength * framerate.Value)
                    );
                }

                args += " " + EncodingHelper.GetVideoQualityParam(state, codec, encodingOptions, GetDefaultEncoderPreset());

                // Unable to force key frames using these hw encoders, set key frames by GOP
                if (string.Equals(codec, "h264_qsv", StringComparison.OrdinalIgnoreCase)
                    || string.Equals(codec, "h264_nvenc", StringComparison.OrdinalIgnoreCase)
                    || string.Equals(codec, "h264_amf", StringComparison.OrdinalIgnoreCase))
                {
                    args += " " + gopArg;
                }
                else
                {
                    args += " " + keyFrameArg + gopArg;
                }

                //args += " -mixed-refs 0 -refs 3 -x264opts b_pyramid=0:weightb=0:weightp=0";

                var hasGraphicalSubs = state.SubtitleStream != null && !state.SubtitleStream.IsTextSubtitleStream && state.SubtitleDeliveryMethod == SubtitleDeliveryMethod.Encode;

                // This is for graphical subs
                if (hasGraphicalSubs)
                {
                    args += EncodingHelper.GetGraphicalSubtitleParam(state, encodingOptions, codec);
                }
                // Add resolution params, if specified
                else
                {
                    args += EncodingHelper.GetOutputSizeParam(state, encodingOptions, codec);
                }

                // -start_at_zero is necessary to use with -ss when seeking,
                // otherwise the target position cannot be determined.
                if (!(state.SubtitleStream != null && state.SubtitleStream.IsExternal && !state.SubtitleStream.IsTextSubtitleStream))
                {
                    args += " -start_at_zero";
                }

                //args += " -flags -global_header";
            }

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

            args += EncodingHelper.GetOutputFFlags(state);

            return args;
        }

        protected override string GetCommandLineArguments(string outputPath, EncodingOptions encodingOptions, StreamState state, bool isEncoding)
        {
            var videoCodec = EncodingHelper.GetVideoEncoder(state, encodingOptions);

            var threads = EncodingHelper.GetNumberOfThreads(state, encodingOptions, videoCodec);

            if (state.BaseRequest.BreakOnNonKeyFrames)
            {
                // FIXME: this is actually a workaround, as ideally it really should be the client which decides whether non-keyframe
                //        breakpoints are supported; but current implementation always uses "ffmpeg input seeking" which is liable
                //        to produce a missing part of video stream before first keyframe is encountered, which may lead to
                //        awkward cases like a few starting HLS segments having no video whatsoever, which breaks hls.js
                Logger.LogInformation("Current HLS implementation doesn't support non-keyframe breaks but one is requested, ignoring that request");
                state.BaseRequest.BreakOnNonKeyFrames = false;
            }

            var inputModifier = EncodingHelper.GetInputModifier(state, encodingOptions);

            // If isEncoding is true we're actually starting ffmpeg
            var startNumber = GetStartNumber(state);
            var startNumberParam = isEncoding ? startNumber.ToString(CultureInfo.InvariantCulture) : "0";

            var mapArgs = state.IsOutputVideo ? EncodingHelper.GetMapArgs(state) : string.Empty;

            var outputTsArg = Path.Combine(Path.GetDirectoryName(outputPath), Path.GetFileNameWithoutExtension(outputPath)) + "%d" + GetSegmentFileExtension(state.Request);

            var segmentFormat = GetSegmentFileExtension(state.Request).TrimStart('.');
            if (string.Equals(segmentFormat, "ts", StringComparison.OrdinalIgnoreCase))
            {
                segmentFormat = "mpegts";
            }

            return string.Format(
                "{0} {1} -map_metadata -1 -map_chapters -1 -threads {2} {3} {4} {5} -copyts -avoid_negative_ts disabled -f hls -max_delay 5000000 -hls_time {6} -individual_header_trailer 0 -hls_segment_type {7} -start_number {8} -hls_segment_filename \"{9}\" -hls_playlist_type vod -hls_list_size 0 -y \"{10}\"",
                inputModifier,
                EncodingHelper.GetInputArgument(state, encodingOptions),
                threads,
                mapArgs,
                GetVideoArguments(state, encodingOptions),
                GetAudioArguments(state, encodingOptions),
                state.SegmentLength.ToString(CultureInfo.InvariantCulture),
                segmentFormat,
                startNumberParam,
                outputTsArg,
                outputPath
            ).Trim();
        }
    }
}