use output duration flag (#49)

* re-enable output duration flag

* calculate appropriate duration for offline image

ErsatzTV.Application/Streaming/Queries/GetPlayoutItemProcessByChannelNumberHandler.cs

@@ -10,7 +10,6 @@ using ErsatzTV.Core.FFmpeg;
 using ErsatzTV.Core.Interfaces.Repositories;
 using LanguageExt;
 using Microsoft.Extensions.Logging;
-using static LanguageExt.Prelude;
 
 namespace ErsatzTV.Application.Streaming.Queries
 {
@@ -69,18 +68,20 @@ namespace ErsatzTV.Application.Streaming.Queries
                         playoutItem.StartOffset,
                         now);
                 },
-                () =>
+                async () =>
                 {
                     if (channel.FFmpegProfile.Transcode)
                     {
-                        return Right<BaseError, Process>(_ffmpegProcessService.ForOfflineImage(ffmpegPath, channel))
-                            .AsTask();
+                        Option<TimeSpan> maybeDuration = await _playoutRepository.GetNextItemStart(channel.Id, now)
+                            .MapT(nextStart => nextStart - now);
+
+                        return _ffmpegProcessService.ForOfflineImage(ffmpegPath, channel, maybeDuration);
                     }
 
                     var message =
                         $"Unable to locate playout item for channel {channel.Number}; offline image is unavailable because transcoding is disabled in ffmpeg profile '{channel.FFmpegProfile.Name}'";
 
-                    return Left<BaseError, Process>(BaseError.New(message)).AsTask();
+                    return BaseError.New(message);
                 });
         }
 

ErsatzTV.Core/FFmpeg/FFmpegProcessBuilder.cs

@@ -227,10 +227,12 @@ namespace ErsatzTV.Core.FFmpeg
                 "1:a");
         }
 
-        public FFmpegProcessBuilder WithDuration(TimeSpan duration) =>
-            // _arguments.Add("-t");
-            // _arguments.Add($"{duration:c}");
-            this;
+        public FFmpegProcessBuilder WithDuration(TimeSpan duration)
+        {
+            _arguments.Add("-t");
+            _arguments.Add($"{duration:c}");
+            return this;
+        }
 
         public FFmpegProcessBuilder WithFormat(string format)
         {

ErsatzTV.Core/FFmpeg/FFmpegProcessService.cs

@@ -2,6 +2,7 @@
 using System.Diagnostics;
 using ErsatzTV.Core.Domain;
 using ErsatzTV.Core.Interfaces.FFmpeg;
+using LanguageExt;
 
 namespace ErsatzTV.Core.FFmpeg
 {
@@ -83,14 +84,14 @@ namespace ErsatzTV.Core.FFmpeg
                 .Build();
         }
 
-        public Process ForOfflineImage(string ffmpegPath, Channel channel)
+        public Process ForOfflineImage(string ffmpegPath, Channel channel, Option<TimeSpan> duration)
         {
             FFmpegPlaybackSettings playbackSettings =
                 _playbackSettingsCalculator.CalculateErrorSettings(channel.FFmpegProfile);
 
             IDisplaySize desiredResolution = channel.FFmpegProfile.Resolution;
 
-            return new FFmpegProcessBuilder(ffmpegPath)
+            FFmpegProcessBuilder builder = new FFmpegProcessBuilder(ffmpegPath)
                 .WithThreads(1)
                 .WithQuiet()
                 .WithFormatFlags(playbackSettings.FormatFlags)
@@ -102,10 +103,11 @@ namespace ErsatzTV.Core.FFmpeg
                 .WithPixfmt("yuv420p")
                 .WithPlaybackArgs(playbackSettings)
                 .WithMetadata(channel)
-                .WithFormat("mpegts")
-                .WithDuration(TimeSpan.FromSeconds(10)) // TODO: figure out when we're back online
-                .WithPipe()
-                .Build();
+                .WithFormat("mpegts");
+
+            duration.IfSome(d => builder = builder.WithDuration(d));
+
+            return builder.WithPipe().Build();
         }
 
         public Process ConcatChannel(string ffmpegPath, Channel channel, string scheme, string host)

ErsatzTV.Core/Interfaces/Repositories/IPlayoutRepository.cs

@@ -12,6 +12,7 @@ namespace ErsatzTV.Core.Interfaces.Repositories
         Task<Option<Playout>> Get(int id);
         Task<Option<Playout>> GetFull(int id);
         Task<Option<PlayoutItem>> GetPlayoutItem(int channelId, DateTimeOffset now);
+        Task<Option<DateTimeOffset>> GetNextItemStart(int channelId, DateTimeOffset now);
         Task<List<PlayoutItem>> GetPlayoutItems(int playoutId);
         Task<List<Playout>> GetAll();
         Task Update(Playout playout);

ErsatzTV.Infrastructure/Data/Repositories/PlayoutRepository.cs

@@ -44,8 +44,8 @@ namespace ErsatzTV.Infrastructure.Data.Repositories
                 .OrderBy(p => p.Id) // https://github.com/dotnet/efcore/issues/22579#issuecomment-694772289
                 .SingleOrDefaultAsync(p => p.Id == id);
 
-        public async Task<Option<PlayoutItem>> GetPlayoutItem(int channelId, DateTimeOffset now) =>
-            await _dbContext.PlayoutItems
+        public Task<Option<PlayoutItem>> GetPlayoutItem(int channelId, DateTimeOffset now) =>
+            _dbContext.PlayoutItems
                 .Where(pi => pi.Playout.ChannelId == channelId)
                 .Where(pi => pi.Start <= now.UtcDateTime && pi.Finish > now.UtcDateTime)
                 .Include(i => i.MediaItem)
@@ -55,7 +55,17 @@ namespace ErsatzTV.Infrastructure.Data.Repositories
                 .ThenInclude(mi => (mi as Movie).MediaVersions)
                 .ThenInclude(mv => mv.MediaFiles)
                 .AsNoTracking()
-                .SingleOrDefaultAsync();
+                .SingleOrDefaultAsync()
+                .Map(Optional);
+
+        public Task<Option<DateTimeOffset>> GetNextItemStart(int channelId, DateTimeOffset now) =>
+            _dbContext.PlayoutItems
+                .Where(pi => pi.Playout.ChannelId == channelId)
+                .Where(pi => pi.Finish > now.UtcDateTime)
+                .OrderBy(pi => pi.Finish)
+                .FirstOrDefaultAsync()
+                .Map(Optional)
+                .MapT(pi => pi.StartOffset);
 
         public Task<List<PlayoutItem>> GetPlayoutItems(int playoutId) =>
             _dbContext.PlayoutItems