What are possible bit-rates of video compressed according to the ITU H.261? Does H.263 yield higher or lower bit-rate than H.261? Write at least three improvements that H.263 has made compared to H.261. Explain why, in motion-compensated MPEG movies, I-frames typically require more bits than P- or B-frames? Write at least three differences (improvements) that MPEG-1 has compared to H.261