Restrict first video frame probing to file protocol (#15557)

MediaBrowser.MediaEncoding/Encoder/MediaEncoder.cs

@@ -511,7 +511,7 @@ namespace MediaBrowser.MediaEncoding.Encoder
                 ? "{0} -i {1} -threads {2} -v warning -print_format json -show_streams -show_chapters -show_format"
                 : "{0} -i {1} -threads {2} -v warning -print_format json -show_streams -show_format";
 
-            if (!isAudio && _proberSupportsFirstVideoFrame)
+            if (protocol == MediaProtocol.File && !isAudio && _proberSupportsFirstVideoFrame)
             {
                 args += " -show_frames -only_first_vframe";
             }