I want to crop of the Pillarboxing that is added to SD video when Downscaling from HD. Most software like the Adobe Suit, Final Cut and QuickTime adds 9 frames on each side. The Source is always 720x576 or 720x486 Therefore I use this command for PAL.
-vf "crop=702:576:9:0:" and define the output resolution with "-s 720x576".
The problem is that the encoded video is pushed ONE Pixel to the right all the time. Which also means that there is one Column of black pixel to the left. If I do the same but only crop of 8 pixels on each side it seems to be centered just fine.
Also worth noting is that there are no error messages when I crop 8 pixels on each side. But when I crop 9 Pixels ffmpeg gives me this varning, "Warning: data is not aligned! This can lead to a speedloss".