Per spec, "While each frame is encoded as a raster scan of 16x16 macroblocks, the frame dimensions are not necessarily evenly divisible by 16. In this case, write ew = 16 - (width & 15) and eh = 16 - (height & 15) for the excess width and height, respectively."

https://cs.chromium.org/chromium/src/media/gpu/vp8_decoder.cc?type=cs&l=68
In vp8_decoder we should align frame size to 16x16, and set the original width and height from header as visible size.