This Recommendation describes requirements with regard to scalable video transmission system over cable network, which is one of the transmission methods for providing additional high resolution video services.
High resolution video formats such as 4K are expected to be one of the ultra-realistic video formats that will be applied to the future video services over cable network infrastructures. In the beginning of the 4K video [b-ITU-R BT.1769][b-ITU-R BT.2020] service, both services of HDTV and 4K video will be simultaneously provided.
Considering the cost of constructing the infrastructure, the current and new services will be provided over the same cable network infrastructure. Furthermore, in the case that 4K video service will be additionally provided over the existing cable network infrastructure, signal receiver (e.g. STB) should be replaced with a new one which supports 4K service. However, it is difficult to change all STB devices in the existing service at the same time Therefore, an additional 4K service will coexist with the current HDTV service.
Distribution systems using scalable video coding technology are one of the effective methods for achieving simultaneous services. Within a general scalable video coding method, the smallest resolution video is coded as the low layer, and then the higher resolution video(s) is/are coded as the higher layer(s) by encoding the difference information from the lower resolution video.
From the viewpoint of compatibility to the current cable services which employs RF-based broadcasting, one solution is that the existing HDTV service over RF is also used as the low layer, and then the difference information between 4K video and HDTV may be transmitted as the higher layer over the IP interface (DOCSIS [ITU-T J.222.0]).
This Recommendation includes requirements of general issues, scalability of video service, and system performance.