diff --git a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
index 27d235affa..e4a8a4cb5c 100644
--- a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
+++ b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
@@ -1578,14 +1578,15 @@ namespace MediaBrowser.Controller.MediaEncoding
 
             int bitrate = state.OutputVideoBitrate.Value;
 
-            // Bit rate under 1000k is not allowed in h264_qsv
+            // Bit rate under 1000k is not allowed in h264_qsv.
             if (string.Equals(videoCodec, "h264_qsv", StringComparison.OrdinalIgnoreCase))
             {
                 bitrate = Math.Max(bitrate, 1000);
             }
 
-            // Currently use the same buffer size for all encoders
-            int bufsize = bitrate * 2;
+            // Currently use the same buffer size for all non-QSV encoders.
+            // Use long arithmetic to prevent int32 overflow for very high bitrate values.
+            int bufsize = (int)Math.Min((long)bitrate * 2, int.MaxValue);
 
             if (string.Equals(videoCodec, "libsvtav1", StringComparison.OrdinalIgnoreCase))
             {
@@ -1613,9 +1614,27 @@ namespace MediaBrowser.Controller.MediaEncoding
                     mbbrcOpt = " -mbbrc 1";
                 }
 
+                // Some less powerful H.264 HW decoders require strict CPB size
+                // So bufsize optimizations should not be applied to them
+                int factor = 2;
+                var codec = state.ActualOutputVideoCodec;
+                var level = state.GetRequestedLevel(codec);
+                if (string.Equals(codec, "h264", StringComparison.OrdinalIgnoreCase)
+                    && double.TryParse(level, CultureInfo.InvariantCulture, out double requestedLevel)
+                    && requestedLevel < 51)
+                {
+                    factor = 1;
+                }
+
                 // Set (maxrate == bitrate + 1) to trigger VBR for better bitrate allocation
                 // Set (rc_init_occupancy == 2 * bitrate) and (bufsize == 4 * bitrate) to deal with drastic scene changes
-                return FormattableString.Invariant($"{mbbrcOpt} -b:v {bitrate} -maxrate {bitrate + 1} -rc_init_occupancy {bitrate * 2} -bufsize {bitrate * 4}");
+                // Use long arithmetic and clamp to int.MaxValue to prevent int32 overflow
+                // (e.g. bitrate * 4 wraps to a negative value for bitrates above ~537 million)
+                int qsvMaxrate = (int)Math.Min((long)bitrate + 1, int.MaxValue);
+                int qsvInitOcc = (int)Math.Min((long)bitrate * 1 * factor, int.MaxValue);
+                int qsvBufsize = (int)Math.Min((long)bitrate * 2 * factor, int.MaxValue);
+
+                return FormattableString.Invariant($"{mbbrcOpt} -b:v {bitrate} -maxrate {qsvMaxrate} -rc_init_occupancy {qsvInitOcc} -bufsize {qsvBufsize}");
             }
 
             if (string.Equals(videoCodec, "h264_amf", StringComparison.OrdinalIgnoreCase)