Add delay_moov flag for progressive mp4 transcoding

MediaBrowser.Controller/MediaEncoding/EncodingHelper.cs

@@ -5569,7 +5569,7 @@ namespace MediaBrowser.Controller.MediaEncoding
                 && state.BaseRequest.Context == EncodingContext.Streaming)
             {
                 // Comparison: https://github.com/jansmolders86/mediacenterjs/blob/master/lib/transcoding/desktop.js
-                format = " -f mp4 -movflags frag_keyframe+empty_moov";
+                format = " -f mp4 -movflags frag_keyframe+empty_moov+delay_moov";
             }
 
             var threads = GetNumberOfThreads(state, encodingOptions, videoCodec);