Update AppStorePreview.md

publishing/AppStorePreview.md

@@ -2,6 +2,6 @@ App Store Preview
 
 - use ios simulator to record screen
 - use iMoive to speed up video (App Preview project)
-- use Adobe online service to resize the video
-- make sure the h246 level not too high `ffmpeg -i input.00.mp4 -s 1200x1600 -filter:v fps=30,scale=1200:1600,setsar=1  -c:v libx264 -profile:v main -level:v 3.1 -c:a copy output.mp4`
-- `ffprobe -loglevel error -show_streams GPlates-App-preview-age-grid.mp4`
+- insert a silent audio channel `ffmpeg -i input.mp4 -f lavfi -i anullsrc -c:v copy -c:a aac -shortest silent.mp4`
+- resize, make sure the h246 level and fps not too high `ffmpeg -i silent.mp4 -filter:v fps=30,scale=1200:1600,setsar=1 -c:v libx264 -profile:v main -level:v 3.1 -c:a copy output.mp4`
+- Check the final video `ffprobe -loglevel error -show_streams GPlates-App-preview-age-grid.mp4`