AOMedia AV1 video codec has been in the works for several years, and has strong industry backing since it's open-source, royalty-free and delivers compression similar or even superior to H.265. Some services like YouTube and Netflix have already started using AV1 on PCs where the CPU is powerful enough to handle software video decoding.
But relying on software video decoding is not ideal on typical Arm-based devices, either because of battery life concerns (e.g. phones) or simply impossible because the processor won't be able to cope. The latter is especially the case on TV boxes who are not usually