Comprehensive test towards advanced terrestrial broadcasting services

NHK has conducted research and development of transmission and related technologies, with the goal of upgrading terrestrial broadcasting services. Comprehensive test was conducted in December 2022 to perform technical verification of a broadcast service to simultaneously transmit multiple 4K programs and 2K programs using a single channel, with the same bandwidth as the current Digital Terrestrial Television Broadcasting, and services integrating broadcast and broadband (Fig. 1).

Since 2019, NHK has been carrying out work for the Association for Promotion of Advanced Broadcasting Services (A-PAB), commissioned by Japan’s Ministry of Internal Affairs and Communications to carry out Technical Test Project*1. For the past four years, NHK has been working to investigate the practical application of new broadcasting services and verify these technologies through large-scale field trials.

In this test, the video and audio of the program were encoded in real time using the latest techniques: Versatile Video Coding (VVC) and MPEG-H 3D Audio. After being encoded, two 4K programs and two 2K programs were input into the software-based master control system*2 and multiplexed on a single IP stream. The multiplexed IP stream containing multiple programs was sent from STRL (Kinuta, Setagaya-ku, Tokyo) (acting as the broadcast station) to the experimental transmitter station (Shiba, Minato-ku, Tokyo) using a dedicated line. It was then sent as an experimental test signal using one channel of the UHF band, through a modulator compatible with the advanced terrestrial broadcasting system.

At the other end, the signal was demodulated using experimental equipment set up at STRL to represent an ordinary home. The 4K and 2K video and audio were decoded and input to a monitor and a 22.2 multichannel sound bar to confirm the video and audio (Fig. 2). The audio signal was compatible with object-based audio*3, demonstrating the potential of the new broadcast service allowing viewers to switch dialogue and adjust sound levels to their own preferences. With the home gateway developed by STRL, the video and audio output by the demodulator were distributed by WiFi. It was confirmed that this enables broadcast content to be viewed with a internet browser on a tunerless device, such as a tablet. It was also confirmed that emergency information output by the software-based master control system could be displayed instantly on the internet browser.

The test further confirmed the technical feasibility of broadcast and broadband integrated services, such as connecting the home gateway to the broadband network to get related content from the cloud; seamlessly switching to a different program in a short time; and viewing 360-degree virtual reality (VR) content synchronized with the broadcast on a tablet (Fig. 3.) These comprehensive tests were open to stakeholders. As well as sharing the progress of research and development towards advanced terrestrial broadcasting services, this has also contributed to a better understanding of research and development.

NHK will continue working on research into the use of broadcast and broadband to deliver services to everyone.

Figure 1. Block diagram of comprehensive test
Figure 2. Exhibition display of broadcast service transmitting 4K programs and 2K programs on a single channel
Figure 3. Exhibition display of broadcast and broadband integrated service
  1. Part of this research was conducted as part of the “Survey and Studies on Technical Measures for Effective Use of Broadcasting Frequencies” for the Technical Examination Services Concerning Frequency Crowding of the Ministry of Internal Affairs and Communications.
  2. A software-based system to implement some of the functions corresponding to a broadcaster’s master control facilities.
  3. An audio system where separate sound elements such as music and voices are transmitted with acoustic metadata, such as reproduction position and volume, then combined at each receiver to create the complete program audio.