NHK Expands On 8K Concert Streaming Project

By Bob Raikes

Back in December 2023, NHK Technologies,Inc. of Japan, the national broadcaster that has been leading many of the developments in 8K TV, captured and streamed a concert of Beethoven’s 9th Symphony, performed by the NHK Symphony Orchestra. The concert took place in Tokyo, but was also intended to be viewed by an audience in Hiroshima in an immersive way. The Hiroshima viewing was watched on a 330 inch 8K projected image with 5.1channel (ch) audio.

We contacted NHK and interviewed Wada-san of that organisation who coordinated the live streaming. Our interview was assisted by Spin Digital Asia Pacific Inc. , the company that supplied the compression technology for the event. The concert was also received and displayed by equipment maker Astrodesign in Tokyo, in 8K with an 8K projector and 22.2ch multi audio and by Spin Digital in Berlin. The Berlin showing used a 8K monitor and 5.1 audio.

8KA: Cinematographers that have used 8K (such as Pawel Achtel who has talked about this) make the point that 8K is a new medium and needs to allow the viewer more time to appreciate the experience. Is this NHK Technologies,Inc.’s view?

NHK-Tech: Yes. The aim of the demonstration was to allow a feeling of immersion, of ‘being there’ for the audience in Hiroshima. If the camera was constantly changing viewpoint, this would not have been successful. It is better with such an 8K image that the viewer’s eyes perform the ‘pan’, not the cameraman. The audience in Hiroshima was not used to 8K and was very impressed. The viewing included bean bag seating to allow some disabled people to join. They might not have been comfortable in a traditional concert hall.

8KA: Were there any special lenses or camera equipment used?

NHK-Tech: It was important from NHK-Tech’s point of view that the live concert was also enjoyable for the audience in the concert hall, so a single small camera with a wide angle lens was required. Special lighting was to be avoided and so the camera needed to be very quiet (with no fan) but also perform will with low video noise at quite low levels of luminance.

 8KA: The signal was streamed using the HEVC codec. Why was that codec chosen?

NHK-Tech: The choice of HEVC rather than, for example, VVC was because of the maturity of the HEVC technology and equipment. HEVC is well developed and understood whereas 8K VVC is still relatively new and being optimized. The content was being streamed to multiple locations and this has not been done so widely or as often with VVC yet.

8KA: How was the video stream delivered? Was there a private network?

NHK-Tech: The stream was delivered over the public internet with a bitrate of 130Mbps and was received well in all the sites.

8KA: In a static camera with orchestra, there is not a lot of large area movement, but a lot of small motions from many players. Did that need any optimisation of the compression parameters?

NHK-Tech: The audio side was more challenging, as it was being distributed in a lossless format but the video side was used with standard parameters and no specific optimization in the codec for this event.

8KA: In the past, the writer was told that when 3D TV was being developed, the audio side was more complicated. Was that the case for the 8K with immersive audio?

NHK-Tech: Yes. There were about 120 microphones to capture the audio from the instruments and the auditorium and they were mapped to the 3D space. The audio was streamed in the 24 ch with metadata and then rendered to the format used (22.2, 5.1 and stereo) at the different locations. 

8KA: Did you get feedback on the immersiveness of the audio?

NHK-Tech: The 22.2ch multi sound was very immersive and the 5.1ch surround presentation gave some sense of presence. However, the stereo sound did not really give a sense of space. In the future, we may look at trying to use binaural stereo to give better depth.

8KA: Do you have plans for this kind of event in the future?

NHK-Tech: We don’t have a fixed plan, but we are very interested in creating premium events that might be available in other parts of the world, perhaps on a pay-per-view basis.