From c6e29647fcdf59ff6f94fc6313edc2e05c9cc32c Mon Sep 17 00:00:00 2001
From: gnattu <gnattuoc@me.com>
Date: Wed, 8 May 2024 08:33:23 +0800
Subject: [PATCH] Recalculate trickplay image height for anamorphic videos

Signed-off-by: gnattu <gnattuoc@me.com>
---
 .../MediaEncoding/EncodingHelper.cs           | 27 ++++++++++++-------
 .../Encoder/MediaEncoder.cs                   | 16 +++++++++++
 2 files changed, 33 insertions(+), 10 deletions(-)

diff --git a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
index 8a8912b2ab..411aafd916 100644
--- a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
+++ b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
@@ -3172,7 +3172,9 @@ namespace MediaBrowser.Controller.MediaEncoding
             int? requestedMaxHeight)
         {
             var isV4l2 = string.Equals(videoEncoder, "h264_v4l2m2m", StringComparison.OrdinalIgnoreCase);
+            var isMjpeg = videoEncoder is not null && videoEncoder.Contains("mjpeg", StringComparison.OrdinalIgnoreCase);
             var scaleVal = isV4l2 ? 64 : 2;
+            var targetAr = isMjpeg ? "(a*sar)" : "a"; // manually calculate AR when using mjpeg encoder
 
             // If fixed dimensions were supplied
             if (requestedWidth.HasValue && requestedHeight.HasValue)
@@ -3201,10 +3203,11 @@ namespace MediaBrowser.Controller.MediaEncoding
 
                 return string.Format(
                     CultureInfo.InvariantCulture,
-                    @"scale=trunc(min(max(iw\,ih*a)\,min({0}\,{1}*a))/{2})*{2}:trunc(min(max(iw/a\,ih)\,min({0}/a\,{1}))/2)*2",
+                    @"scale=trunc(min(max(iw\,ih*{3})\,min({0}\,{1}*{3}))/{2})*{2}:trunc(min(max(iw/{3}\,ih)\,min({0}/{3}\,{1}))/2)*2",
                     maxWidthParam,
                     maxHeightParam,
-                    scaleVal);
+                    scaleVal,
+                    targetAr);
             }
 
             // If a fixed width was requested
@@ -3220,8 +3223,9 @@ namespace MediaBrowser.Controller.MediaEncoding
 
                 return string.Format(
                     CultureInfo.InvariantCulture,
-                    "scale={0}:trunc(ow/a/2)*2",
-                    widthParam);
+                    "scale={0}:trunc(ow/{1}/2)*2",
+                    widthParam,
+                    targetAr);
             }
 
             // If a fixed height was requested
@@ -3231,9 +3235,10 @@ namespace MediaBrowser.Controller.MediaEncoding
 
                 return string.Format(
                     CultureInfo.InvariantCulture,
-                    "scale=trunc(oh*a/{1})*{1}:{0}",
+                    "scale=trunc(oh*{2}/{1})*{1}:{0}",
                     heightParam,
-                    scaleVal);
+                    scaleVal,
+                    targetAr);
             }
 
             // If a max width was requested
@@ -3243,9 +3248,10 @@ namespace MediaBrowser.Controller.MediaEncoding
 
                 return string.Format(
                     CultureInfo.InvariantCulture,
-                    @"scale=trunc(min(max(iw\,ih*a)\,{0})/{1})*{1}:trunc(ow/a/2)*2",
+                    @"scale=trunc(min(max(iw\,ih*{2})\,{0})/{1})*{1}:trunc(ow/{2}/2)*2",
                     maxWidthParam,
-                    scaleVal);
+                    scaleVal,
+                    targetAr);
             }
 
             // If a max height was requested
@@ -3255,9 +3261,10 @@ namespace MediaBrowser.Controller.MediaEncoding
 
                 return string.Format(
                     CultureInfo.InvariantCulture,
-                    @"scale=trunc(oh*a/{1})*{1}:min(max(iw/a\,ih)\,{0})",
+                    @"scale=trunc(oh*{2}/{1})*{1}:min(max(iw/{2}\,ih)\,{0})",
                     maxHeightParam,
-                    scaleVal);
+                    scaleVal,
+                    targetAr);
             }
 
             return string.Empty;
diff --git a/MediaBrowser.MediaEncoding/Encoder/MediaEncoder.cs b/MediaBrowser.MediaEncoding/Encoder/MediaEncoder.cs
index 8ea0f58ea3..387571cdb5 100644
--- a/MediaBrowser.MediaEncoding/Encoder/MediaEncoder.cs
+++ b/MediaBrowser.MediaEncoding/Encoder/MediaEncoder.cs
@@ -824,6 +824,22 @@ namespace MediaBrowser.MediaEncoding.Encoder
                 options.EnableTonemapping = false;
             }
 
+            if (imageStream.Width is not null && imageStream.Height is not null)
+            {
+                // For hardware trickplay encoders, we need to re-calculate the size because they used fixed scale dimensions
+                var darParts = imageStream.AspectRatio.Split(":");
+                var (wa, ha) = (int.Parse(darParts[0], CultureInfo.InvariantCulture), int.Parse(darParts[1], CultureInfo.InvariantCulture));
+                // When dimension / DAR does not equal to 1:1, then the frames are most likely stored stretched.
+                // Note: this might be incorrect for 3D videos as the SAR stored might be per eye instead of per video, but we really can do little about it.
+                var shouldResetHeight = imageStream.Width * ha != imageStream.Height * wa;
+                if (shouldResetHeight)
+                {
+                    // SAR = DAR * Height / Width
+                    // RealHeight = Height / SAR = Height / (DAR * Height / Width) = Width / DAR
+                    imageStream.Height = Convert.ToInt32(imageStream.Width.Value * (double)ha / wa);
+                }
+            }
+
             var baseRequest = new BaseEncodingJobOptions { MaxWidth = maxWidth, MaxFramerate = (float)(1.0 / interval.TotalSeconds) };
             var jobState = new EncodingJobInfo(TranscodingJobType.Progressive)
             {