Metadata key ignore case

Bmp.Core/FFMpeg/CsCorePorts/FFMpegWrap/AvFormatContext.cs

@@ -83,13 +83,13 @@ internal class AvFormatContext : IDisposable
         BestAudioStreamIndex = FfmpegCalls.AvFindBestStreamInfo(_formatContext);
         _stream = new AvStream((nint)_formatContext->streams[BestAudioStreamIndex]);
 
-        Metadata = new Dictionary<string, string>();
+        Metadata = new Dictionary<string, string>(StringComparer.OrdinalIgnoreCase);
         if (_formatContext->metadata != null)
         {
             var metadata = _formatContext->metadata->Elements;
             foreach (var element in metadata)
             {
-                Metadata.Add(element.Key, element.Value);
+                Metadata[element.Key]= element.Value;
             }
         }
     }