Modern video codecs do a much more efficient job when the horizontal and vertical framesize dimensions are multiples of 16. Good examples include:
SD (4:3) aspect ratios: 320x240, 432x320, 480x360, 576x432, 640x480, 720x540, 768x576
HD (16:9) aspect ratios: 432x240, 576x320, 640x360, 768x432, 848x480, 960x540, 1024x576, 1280x720, 1536x864, 1920x1080
In 4:2:0 H.264/AVC coding, each block contains 4 luminance samples (Y), 1 blue sample (Cb), and 1 red sample (Cr). Modern video decoding chips (GPUs) are optimized for playback of 16x16 macroblocking.
For HD videos, please use high video profile, see tags below. HD videos may stutter during playback on older computers or devices with low-end graphics hardware.
PROFILES
Baseline - for low definition (LD) 320x240 or smaller, compatible with older 3G mobiles
Main - for standard definition (SD) to 640x480, good for modern smartphones and tablets
High - for high definition (HD) to 1920x1080, best for big screens with a good decoder
