Review usage of string.Substring (part 1)

Reduced allocations by replacing string.Substring with ReadOnlySpan<char>.Slice

1 files changed, 11 insertions, 12 deletions

diff --git a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
index ffbda42c3..18fd53ad6 100644
--- a/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
+++ b/MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs
@@ -1588,7 +1588,7 @@ namespace MediaBrowser.Controller.MediaEncoding
         {
             outputVideoCodec ??= string.Empty;
 
-            var outputSizeParam = string.Empty;
+            var outputSizeParam = ReadOnlySpan<char>.Empty;
             var request = state.BaseRequest;
 
             // Add resolution params, if specified
@@ -1602,28 +1602,28 @@ namespace MediaBrowser.Controller.MediaEncoding
                 var index = outputSizeParam.IndexOf("hwdownload", StringComparison.OrdinalIgnoreCase);
                 if (index != -1)
                 {
-                    outputSizeParam = outputSizeParam.Substring(index);
+                    outputSizeParam = outputSizeParam.Slice(index);
                 }
                 else
                 {
                     index = outputSizeParam.IndexOf("format", StringComparison.OrdinalIgnoreCase);
                     if (index != -1)
                     {
-                        outputSizeParam = outputSizeParam.Substring(index);
+                        outputSizeParam = outputSizeParam.Slice(index);
                     }
                     else
                     {
                         index = outputSizeParam.IndexOf("yadif", StringComparison.OrdinalIgnoreCase);
                         if (index != -1)
                         {
-                            outputSizeParam = outputSizeParam.Substring(index);
+                            outputSizeParam = outputSizeParam.Slice(index);
                         }
                         else
                         {
                             index = outputSizeParam.IndexOf("scale", StringComparison.OrdinalIgnoreCase);
                             if (index != -1)
                             {
-                                outputSizeParam = outputSizeParam.Substring(index);
+                                outputSizeParam = outputSizeParam.Slice(index);
                             }
                         }
                     }
@@ -1669,9 +1669,9 @@ namespace MediaBrowser.Controller.MediaEncoding
 
             // Setup default filtergraph utilizing FFMpeg overlay() and FFMpeg scale() (see the return of this function for index reference)
             // Always put the scaler before the overlay for better performance
-            var retStr = !string.IsNullOrEmpty(outputSizeParam) ?
-                " -filter_complex \"[{0}:{1}]{4}[sub];[0:{2}]{3}[base];[base][sub]overlay\"" :
-                " -filter_complex \"[{0}:{1}]{4}[sub];[0:{2}][sub]overlay\"";
+            var retStr = !outputSizeParam.IsEmpty
+                ? " -filter_complex \"[{0}:{1}]{4}[sub];[0:{2}]{3}[base];[base][sub]overlay\""
+                : " -filter_complex \"[{0}:{1}]{4}[sub];[0:{2}][sub]overlay\"";
 
             // When the input may or may not be hardware VAAPI decodable
             if (string.Equals(outputVideoCodec, "h264_vaapi", StringComparison.OrdinalIgnoreCase))
@@ -1705,7 +1705,7 @@ namespace MediaBrowser.Controller.MediaEncoding
                 */
                 if (isLinux)
                 {
-                    retStr = !string.IsNullOrEmpty(outputSizeParam) ?
+                    retStr = !outputSizeParam.IsEmpty ?
                         " -filter_complex \"[{0}:{1}]{4}[sub];[0:{2}]{3}[base];[base][sub]overlay_qsv\"" :
                         " -filter_complex \"[{0}:{1}]{4}[sub];[0:{2}][sub]overlay_qsv\"";
                 }
@@ -1717,7 +1717,7 @@ namespace MediaBrowser.Controller.MediaEncoding
                 mapPrefix,
                 subtitleStreamIndex,
                 state.VideoStream.Index,
-                outputSizeParam,
+                outputSizeParam.ToString(),
                 videoSizeParam);
         }
 
@@ -2090,7 +2090,7 @@ namespace MediaBrowser.Controller.MediaEncoding
             // Add software deinterlace filter before scaling filter
             if (state.DeInterlace("h264", true) || state.DeInterlace("h265", true) || state.DeInterlace("hevc", true))
             {
-                var deintParam = string.Empty;
+                string deintParam;
                 var inputFramerate = videoStream?.RealFrameRate;
 
                 // If it is already 60fps then it will create an output framerate that is much too high for roku and others to handle
@@ -2159,7 +2159,6 @@ namespace MediaBrowser.Controller.MediaEncoding
             return output;
         }
 
-
         /// <summary>
         /// Gets the number of threads.
         /// </summary>