Merge pull request #6222 from orryverducci/mbaff-interlace-detection

MediaBrowser.MediaEncoding/Probing/ProbeResultNormalizer.cs

@@ -649,11 +649,6 @@ namespace MediaBrowser.MediaEncoding.Probing
                 stream.IsAVC = false;
             }
 
-            if (!string.IsNullOrWhiteSpace(streamInfo.FieldOrder) && !string.Equals(streamInfo.FieldOrder, "progressive", StringComparison.OrdinalIgnoreCase))
-            {
-                stream.IsInterlaced = true;
-            }
-
             // Filter out junk
             if (!string.IsNullOrWhiteSpace(streamInfo.CodecTagString) && !streamInfo.CodecTagString.Contains("[0]", StringComparison.OrdinalIgnoreCase))
             {
@@ -725,6 +720,23 @@ namespace MediaBrowser.MediaEncoding.Probing
                 stream.AverageFrameRate = GetFrameRate(streamInfo.AverageFrameRate);
                 stream.RealFrameRate = GetFrameRate(streamInfo.RFrameRate);
 
+                // Some interlaced H.264 files in mp4 containers using MBAFF coding aren't flagged as being interlaced by FFprobe,
+                // so for H.264 files we also calculate the frame rate from the codec time base and check if it is double the reported
+                // frame rate (both rounded to the nearest integer) to determine if the file is interlaced
+                float roundedTimeBaseFPS = MathF.Round(1 / GetFrameRate(stream.CodecTimeBase) ?? 0);
+                float roundedDoubleFrameRate = MathF.Round(stream.AverageFrameRate * 2 ?? 0);
+
+                bool videoInterlaced = !string.IsNullOrWhiteSpace(streamInfo.FieldOrder)
+                    && !string.Equals(streamInfo.FieldOrder, "progressive", StringComparison.OrdinalIgnoreCase);
+                bool h264MbaffCoded = string.Equals(stream.Codec, "h264", StringComparison.OrdinalIgnoreCase)
+                    && string.IsNullOrWhiteSpace(streamInfo.FieldOrder)
+                    && roundedTimeBaseFPS == roundedDoubleFrameRate;
+
+                if (videoInterlaced || h264MbaffCoded)
+                {
+                    stream.IsInterlaced = true;
+                }
+
                 if (isAudio
                     || string.Equals(stream.Codec, "mjpeg", StringComparison.OrdinalIgnoreCase)
                     || string.Equals(stream.Codec, "gif", StringComparison.OrdinalIgnoreCase)