Whether you are encoding to QuickTime or Flash Video, it is a best practice to ensure that the width and height of your video is evenly divisible by 16. Although some modern codecs do not require this, it is best to keep it in mind for all your projects to guarantee the best results.
In many codecs if a side is not divisible by 16 evenly, it will then have to keep splitting the macro blocks into smaller and smaller chunks until it finds a common denominator. This can result in lots of tiny little blocks in your video, and horrible encodes, especially for high action and/or animation sequences.
Robert Reinhardt has posted a table listing the optimal frame dimensions for flash video for both 16:9 and 4:3 aspect ratios. This information is a great resource for every compressionist.
http://www.flashsupport.com/books/fvst/files/tools/video_sizes.html
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4 Comments
Thanks for great information. I have one qustion: Should it divisible by 16 before or after croping? Should the crop be even?
Your final encoded frame size should be evenly divisible by 16 (after cropping, scaling, etc)
So how come 1080p standard is not evenly divisible? (1080/16=67.5)
That is a good question… it is evenly divisible by 4 and 8 though. From what I understand the 16x macroblock issue only applies to MP4 codecs, so it is not really specific to HD or SD.