From ea5956a2687e28398c6146430fc9e00c0287952f Mon Sep 17 00:00:00 2001
From: Jason Dove <1695733+jasongdove@users.noreply.github.com>
Date: Mon, 13 Oct 2025 16:26:06 -0500
Subject: [PATCH] improve stream startup (#2525)

---
 CHANGELOG.md                                  |  1 +
 .../Streaming/HlsSessionWorker.cs             |  4 +--
 ...layoutItemProcessByChannelNumberHandler.cs | 18 ++++++++++-
 .../Pipeline/PipelineBuilderBase.cs           | 31 +++++++++----------
 4 files changed, 33 insertions(+), 21 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2f36d61c1..c4d1c1c99 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -28,6 +28,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Fix playback troubleshooting selecting a subtitle even with no subtitle stream selected in the UI
 - Fix intermittent watermark opacity
 - Improve reliability of live remote streams; they should transcode closer to realtime in most cases
+- Dramatically improve stream startup time
 
 ### Changed
 - Do not use graphics engine for single, permanent watermark
diff --git a/ErsatzTV.Application/Streaming/HlsSessionWorker.cs b/ErsatzTV.Application/Streaming/HlsSessionWorker.cs
index 6a676e5f7..2a2ae3ca0 100644
--- a/ErsatzTV.Application/Streaming/HlsSessionWorker.cs
+++ b/ErsatzTV.Application/Streaming/HlsSessionWorker.cs
@@ -393,9 +393,7 @@ public class HlsSessionWorker : IHlsSessionWorker
         return result;
     }
 
-    private async Task<bool> Transcode(
-        bool realtime,
-        CancellationToken cancellationToken)
+    private async Task<bool> Transcode(bool realtime, CancellationToken cancellationToken)
     {
         try
         {
diff --git a/ErsatzTV.Application/Streaming/Queries/GetPlayoutItemProcessByChannelNumberHandler.cs b/ErsatzTV.Application/Streaming/Queries/GetPlayoutItemProcessByChannelNumberHandler.cs
index 06cdc330b..f1858110f 100644
--- a/ErsatzTV.Application/Streaming/Queries/GetPlayoutItemProcessByChannelNumberHandler.cs
+++ b/ErsatzTV.Application/Streaming/Queries/GetPlayoutItemProcessByChannelNumberHandler.cs
@@ -281,6 +281,22 @@ public class GetPlayoutItemProcessByChannelNumberHandler : FFmpegProcessHandler<
             DateTimeOffset effectiveNow = request.StartAtZero ? start : now;
             TimeSpan duration = finish - effectiveNow;
 
+            bool isComplete = true;
+
+            // if we are working ahead, limit to 45s
+            if (!request.HlsRealtime)
+            {
+                TimeSpan limit = TimeSpan.FromSeconds(45);
+
+                if (duration > limit)
+                {
+                    finish = effectiveNow + limit;
+                    outPoint = inPoint + limit;
+                    duration = limit;
+                    isComplete = false;
+                }
+            }
+
             if (_isDebugNoSync)
             {
                 Command doesNotExistProcess = await _ffmpegProcessService.ForError(
@@ -427,7 +443,7 @@ public class GetPlayoutItemProcessByChannelNumberHandler : FFmpegProcessHandler<
                 playoutItemResult.GraphicsEngineContext,
                 duration,
                 finish,
-                true);
+                isComplete);
 
             return Right<BaseError, PlayoutItemProcessModel>(result);
         }
diff --git a/ErsatzTV.FFmpeg/Pipeline/PipelineBuilderBase.cs b/ErsatzTV.FFmpeg/Pipeline/PipelineBuilderBase.cs
index 1d31d16c5..d8e6207c0 100644
--- a/ErsatzTV.FFmpeg/Pipeline/PipelineBuilderBase.cs
+++ b/ErsatzTV.FFmpeg/Pipeline/PipelineBuilderBase.cs
@@ -563,7 +563,7 @@ public abstract class PipelineBuilderBase : IPipelineBuilder
             : SetDecoder(videoInputFile, videoStream, ffmpegState, context);
 
         //SetStillImageInfiniteLoop(videoInputFile, videoStream, ffmpegState);
-        SetRealtimeInput(videoInputFile, desiredState);
+        SetRealtimeInput(videoInputFile, ffmpegState, desiredState);
         SetInfiniteLoop(videoInputFile, videoStream, ffmpegState, desiredState);
         SetFrameRateOutput(desiredState, pipelineSteps);
         SetVideoTrackTimescaleOutput(desiredState, pipelineSteps);
@@ -760,29 +760,26 @@ public abstract class PipelineBuilderBase : IPipelineBuilder
         }
     }
 
-    private void SetRealtimeInput(VideoInputFile videoInputFile, FrameState desiredState)
+    private void SetRealtimeInput(VideoInputFile videoInputFile, FFmpegState ffmpegState, FrameState desiredState)
     {
-        if (videoInputFile.StreamInputKind is StreamInputKind.Live)
+        if (videoInputFile.StreamInputKind is StreamInputKind.Live || !desiredState.Realtime)
         {
             return;
         }
 
-        int initialBurst;
-        if (!desiredState.Realtime)
-        {
-            initialBurst = 45;
-        }
-        else
+        AudioFilter filter = _audioInputFile
+            .Map(a => a.DesiredState.NormalizeLoudnessFilter)
+            .IfNone(AudioFilter.None);
+
+        int initialBurst = filter switch
         {
-            AudioFilter filter = _audioInputFile
-                .Map(a => a.DesiredState.NormalizeLoudnessFilter)
-                .IfNone(AudioFilter.None);
+            AudioFilter.LoudNorm => 5,
+            _ => 0
+        };
 
-            initialBurst = filter switch
-            {
-                AudioFilter.LoudNorm => 5,
-                _ => 0
-            };
+        if (ffmpegState.Finish.Any(finish => finish.TotalSeconds < initialBurst))
+        {
+            return;
         }
 
         _audioInputFile.Iter(a => a.AddOption(new ReadrateInputOption(_ffmpegCapabilities, initialBurst, _logger)));