This work presents a coding efficiency evaluation of the recently published first release of the video coding scheme of the Alliance for Open Media (AOM), so called AOM/AV1, in comparison to the video coding standards H.264/MPEG-AVC (Advanced Video Coding) and H.265/MPEG-HEVC (High-Efficiency Video Coding). As representatives of the two last-mentioned video coding standards, the corresponding reference software encoders of JM and HM were selected, and for HEVC, in addition, the Fraunhofer HHI HEVC commercial software encoder and the open source software implementation x265 were used. According to the experimental results, which were obtained by using similar configurations for all examined representative encoders, the H.265/MPEG-HEVC reference software implementation provides significant average bit-rate savings of 38.4 % and 32.8 % compared to AOM/AV1 and H.264/MPEG-AVC, respectively. Particularly, when directly compared to H.264/MPEG-AVC High Profile, the AOM/AV1 encoder produces an average bit-rate overhead of 10.5% at the same objective quality. In addition, it was observed that the AOM/AV1 encoding times are quite similar to those of the full-fledged HM and JM reference software encoders. On the other hand, the typical encoding times of the HM encoder are in the range of 30-300 times higher on average than those measured for the configurable HHI HEVC encoder, depending on its chosen trade-off between encoding speed and coding efficiency.