add hls segmenter initial segment count (#616)

CHANGELOG.md

@@ -14,6 +14,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Include `Series` category tag for all episodes in XMLTV
 - Include movie, episode (show), music video (artist) genres as `category` tags in XMLTV
 - Add framerate normalization to `HLS Segmenter` and `MPEG-TS` streaming modes
+- Add `HLS Segmenter Initial Segment Count` setting to allow segmenter to work ahead before allowing client playback
 
 ### Changed
 - Intermittent watermarks will now fade in and out

ErsatzTV.Application/FFmpegProfiles/Commands/UpdateFFmpegSettingsHandler.cs

@@ -119,6 +119,10 @@ namespace ErsatzTV.Application.FFmpegProfiles.Commands
                 ConfigElementKey.FFmpegWorkAheadSegmenters,
                 request.Settings.WorkAheadSegmenterLimit);
 
+            await _configElementRepository.Upsert(
+                ConfigElementKey.FFmpegInitialSegmentCount,
+                request.Settings.InitialSegmentCount);
+
             return Unit.Default;
         }
     }

ErsatzTV.Application/FFmpegProfiles/FFmpegSettingsViewModel.cs

@@ -11,5 +11,6 @@
         public int? GlobalFallbackFillerId { get; set; }
         public int HlsSegmenterIdleTimeout { get; set; }
         public int WorkAheadSegmenterLimit { get; set; }
+        public int InitialSegmentCount { get; set; }
     }
 }

ErsatzTV.Application/FFmpegProfiles/Queries/GetFFmpegSettingsHandler.cs

@@ -34,6 +34,8 @@ namespace ErsatzTV.Application.FFmpegProfiles.Queries
                 await _configElementRepository.GetValue<int>(ConfigElementKey.FFmpegSegmenterTimeout);
             Option<int> workAheadSegmenterLimit =
                 await _configElementRepository.GetValue<int>(ConfigElementKey.FFmpegWorkAheadSegmenters);
+            Option<int> initialSegmentCount =
+                await _configElementRepository.GetValue<int>(ConfigElementKey.FFmpegInitialSegmentCount);
 
             var result = new FFmpegSettingsViewModel
             {
@@ -44,6 +46,7 @@ namespace ErsatzTV.Application.FFmpegProfiles.Queries
                 PreferredLanguageCode = await preferredLanguageCode.IfNoneAsync("eng"),
                 HlsSegmenterIdleTimeout = await hlsSegmenterIdleTimeout.IfNoneAsync(60),
                 WorkAheadSegmenterLimit = await workAheadSegmenterLimit.IfNoneAsync(1),
+                InitialSegmentCount = await initialSegmentCount.IfNoneAsync(4)
             };
 
             foreach (int watermarkId in watermark)

ErsatzTV.Application/Streaming/Commands/StartFFmpegSessionHandler.cs

@@ -5,6 +5,7 @@ using System.Threading.Tasks;
 using ErsatzTV.Core;
 using ErsatzTV.Core.Domain;
 using ErsatzTV.Core.Errors;
+using ErsatzTV.Core.FFmpeg;
 using ErsatzTV.Core.Interfaces.FFmpeg;
 using ErsatzTV.Core.Interfaces.Metadata;
 using ErsatzTV.Core.Interfaces.Repositories;
@@ -50,7 +51,7 @@ namespace ErsatzTV.Application.Streaming.Commands
             TimeSpan idleTimeout = await _configElementRepository
                 .GetValue<int>(ConfigElementKey.FFmpegSegmenterTimeout)
                 .Map(maybeTimeout => maybeTimeout.Match(i => TimeSpan.FromSeconds(i), () => TimeSpan.FromMinutes(1)));
-            
+
             using IServiceScope scope = _serviceScopeFactory.CreateScope();
             HlsSessionWorker worker = scope.ServiceProvider.GetRequiredService<HlsSessionWorker>();
             _ffmpegSegmenterService.SessionWorkers.AddOrUpdate(request.ChannelNumber, _ => worker, (_, _) => worker);
@@ -68,12 +69,32 @@ namespace ErsatzTV.Application.Streaming.Commands
                 request.ChannelNumber,
                 "live.m3u8");
 
+            IConfigElementRepository repo = scope.ServiceProvider.GetRequiredService<IConfigElementRepository>();
+            int initialSegmentCount = await repo.GetValue<int>(ConfigElementKey.FFmpegInitialSegmentCount)
+                .Map(maybeCount => maybeCount.Match(identity, () => 4));
+
+            await WaitForPlaylistSegments(playlistFileName, initialSegmentCount, worker);
+
+            return Unit.Default;
+        }
+
+        private static async Task WaitForPlaylistSegments(string playlistFileName, int initialSegmentCount, IHlsSessionWorker worker)
+        {
             while (!File.Exists(playlistFileName))
             {
                 await Task.Delay(TimeSpan.FromMilliseconds(100));
             }
 
-            return Unit.Default;
+            var segmentCount = 0;
+            while (segmentCount < initialSegmentCount)
+            {
+                await Task.Delay(TimeSpan.FromMilliseconds(200));
+                
+                DateTimeOffset now = DateTimeOffset.Now.AddSeconds(-30);
+                string[] input = await File.ReadAllLinesAsync(playlistFileName);
+                TrimPlaylistResult result = HlsPlaylistFilter.TrimPlaylist(worker.PlaylistStart, now, input);
+                segmentCount = result.SegmentCount;
+            }
         }
 
         private Task<Validation<BaseError, Unit>> Validate(StartFFmpegSession request) =>

ErsatzTV.Application/Streaming/HlsSessionWorker.cs

@@ -231,16 +231,31 @@ namespace ErsatzTV.Application.Streaming
                 await File.WriteAllTextAsync(playlistFileName, trimResult.Playlist, cancellationToken);
 
                 // delete old segments
-                foreach (string file in Directory.GetFiles(
-                    Path.Combine(FileSystemLayout.TranscodeFolder, channelNumber),
-                    "*.ts"))
+                var allSegments = Directory.GetFiles(
+                        Path.Combine(FileSystemLayout.TranscodeFolder, channelNumber),
+                        "live*.ts")
+                    .Map(
+                        file =>
+                        {
+                            string fileName = Path.GetFileName(file);
+                            var sequenceNumber = int.Parse(fileName.Replace("live", string.Empty).Split('.')[0]);
+                            return new Segment(file, sequenceNumber);
+                        })
+                    .ToList();
+
+                var toDelete = allSegments.Filter(s => s.SequenceNumber < trimResult.Sequence).ToList();
+                // if (toDelete.Count > 0)
+                // {
+                    // _logger.LogInformation(
+                    //     "Deleting HLS segments {Min} to {Max} (less than {StartSequence})",
+                    //     toDelete.Map(s => s.SequenceNumber).Min(),
+                    //     toDelete.Map(s => s.SequenceNumber).Max(),
+                    //     trimResult.Sequence);
+                // }
+                    
+                foreach (Segment segment in toDelete)
                 {
-                    string fileName = Path.GetFileName(file);
-                    if (fileName.StartsWith("live") && int.Parse(fileName.Replace("live", string.Empty).Split('.')[0]) <
-                        trimResult.Sequence)
-                    {
-                        File.Delete(file);
-                    }
+                    File.Delete(segment.File);
                 }
 
                 _playlistStart = trimResult.PlaylistStart;
@@ -276,5 +291,7 @@ namespace ErsatzTV.Application.Streaming
             return await repo.GetValue<int>(ConfigElementKey.FFmpegWorkAheadSegmenters)
                 .Map(maybeCount => maybeCount.Match(identity, () => 1));
         }
+
+        private record Segment(string File, int SequenceNumber);
     }
 }

ErsatzTV.Core/Domain/ConfigElementKey.cs

@@ -16,6 +16,7 @@
         public static ConfigElementKey FFmpegGlobalFallbackFillerId => new("ffmpeg.global_fallback_filler_id");
         public static ConfigElementKey FFmpegSegmenterTimeout => new("ffmpeg.segmenter.timeout_seconds");
         public static ConfigElementKey FFmpegWorkAheadSegmenters => new("ffmpeg.segmenter.work_ahead_limit");
+        public static ConfigElementKey FFmpegInitialSegmentCount => new("ffmpeg.segmenter.initial_segment_count");
         public static ConfigElementKey SearchIndexVersion => new("search_index.version");
         public static ConfigElementKey HDHRTunerCount => new("hdhr.tuner_count");
         public static ConfigElementKey ChannelsPageSize => new("pages.channels.page_size");

ErsatzTV.Core/FFmpeg/HlsPlaylistFilter.cs

@@ -95,12 +95,13 @@ namespace ErsatzTV.Core.FFmpeg
                 i += 3;
             }
 
-            if (endWithDiscontinuity)
+            var playlist = output.ToString();
+            if (endWithDiscontinuity && !playlist.EndsWith($"#EXT-X-DISCONTINUITY{Environment.NewLine}"))
             {
-                output.AppendLine("#EXT-X-DISCONTINUITY");
+                playlist += "#EXT-X-DISCONTINUITY" + Environment.NewLine;
             }
 
-            return new TrimPlaylistResult(nextPlaylistStart, startSequence, output.ToString());
+            return new TrimPlaylistResult(nextPlaylistStart, startSequence, playlist, segments);
         }
 
         public static TrimPlaylistResult TrimPlaylistWithDiscontinuity(
@@ -112,5 +113,5 @@ namespace ErsatzTV.Core.FFmpeg
         }
     }
 
-    public record TrimPlaylistResult(DateTimeOffset PlaylistStart, int Sequence, string Playlist);
+    public record TrimPlaylistResult(DateTimeOffset PlaylistStart, int Sequence, string Playlist, int SegmentCount);
 }

ErsatzTV/Controllers/IptvController.cs

@@ -92,6 +92,11 @@ namespace ErsatzTV.Controllers
                 {
                     string[] input = await System.IO.File.ReadAllLinesAsync(fileName);
 
+                    // _logger.LogInformation(
+                    //     "Trimming playlist: {PlaylistStart} {FilterBefore}",
+                    //     worker.PlaylistStart,
+                    //     now);
+
                     TrimPlaylistResult result = HlsPlaylistFilter.TrimPlaylist(worker.PlaylistStart, now, input);
                     return Content(result.Playlist, "application/vnd.apple.mpegurl");
                 }

ErsatzTV/Pages/Settings.razor

@@ -94,6 +94,14 @@
                                       Required="true"
                                       RequiredError="Work-ahead HLS Segmenter limit is required!"/>
                     </MudElement>
+                    <MudElement HtmlTag="div" Class="mt-3">
+                        <MudTextField T="int"
+                                      Label="HLS Segmenter Initial Segment Count"
+                                      @bind-Value="_ffmpegSettings.InitialSegmentCount"
+                                      Validation="@(new Func<int, string>(ValidateInitialSegmentCount))"
+                                      Required="true"
+                                      RequiredError="HLS Segmenter initial segment count is required!"/>
+                    </MudElement>
                 </MudForm>
             </MudCardContent>
             <MudCardActions>
@@ -206,6 +214,8 @@
 
     private static string ValidateWorkAheadSegmenterLimit(int limit) => limit < 0 ? "Work-Ahead HLS Segmenter limit must be greater than or equal to 0" : null;
 
+    private static string ValidateInitialSegmentCount(int count) => count < 1 ? "HLS Segmenter initial segment count must be greater than or equal to 1" : null;
+
     private async Task LoadFFmpegProfilesAsync() =>
         _ffmpegProfiles = await _mediator.Send(new GetAllFFmpegProfiles());