In this paper we present an enhancement to the video quality estimation model described in ITU-T Recommendation G.1070 “Opinion model for video-telephony applications”, including the effect of video content in the G.1070 video quality function. This enhancement provides a much better approximation of the model results with respect to the perceptual MOS values. SAD (Sum of Absolute Differences) is used as an estimation of the video spatial-temporal activity. The results are based on more than 1500 processed video clips, coded in MPEG-2 and H.264/AVC, in bit rate ranges from 50 kb/s to 12 Mb/s, in SD, VGA, CIF and QCIF display formats.