NTT develops LSI-based 8K HEVC real-time encoder

Monday, February 15th, 2016
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NTT develops the worlds’ best performance 8K HEVC real-time encoder through dedicated LSI use

  • enabling immersive high-quality 8K video transmission at 85 Mbps

Nippon Telegraph and Telephone (NTT) Corporation (Head office, Chiyoda-ku, Tokyo, Japan; Hiroo Unoura, President and CEO) has developed the worlds’ best performance high-quality 8K HEVC real-time encoder through the use of dedicated LSI’s, which is the key to immersive high-quality 8K video services.

In March 2015, NTT announced a real-time 4K/60p ultra-high definition video encoder LSI (NARA) that conforms with H.265/HEVC (hereafter HEVC), the latest international video coding standard. NTT has developed a high-quality and high-efficiency 8K/60p HEVC real-time encoder operating in conjunction with four LSIs and performing mutual data transmission between them.

This 8K encoder enables immersive high-quality 8K video transmission at 85 Mbps and also enables the 8K encoding process to become economically feasible on one board. This accelerates 8K video distribution services, such as public viewing and ODS (Other Digital Stuff/Other Digital Sources), and 8K broadcast services, and contributes to new application creation in the medical and surveillance fields.

Development Background

Recently, ultra-high definition 4K video services with high realistic sensation have attracted attention. The NTT group has been participating in Japanese government-related business projects and working towards the promotion of ultra-high definition 4K/8K video services. From 2015 on 4K video services, such as satellite broadcasting, IPTV and CATV services, started to become widespread. But 8K video has four times as many pixels as 4K video and thus provides greater reality. It therefore requires a real-time encoder that not only has high compression efficiency but is also small and economical.

NTT laboratories have been researching and developing the technologies needed for 8K video services to become widespread. These technologies are based on those that have been cultivated in the development of encoder LSIs.

Technical Points

NTT laboratories have developed the worlds’ best performance high-quality 8K HEVC real-time encoder by using four chips of the HEVC real-time encoder LSI (NARA). The encoder was developed in order to enable high-quality 8K video services with high realistic sensation.

The encoder’s technical points are described below

(1) Highly efficient, high-quality encoding enabled by mutual data transfer among chips

This 8K encoder adopts a parallel encoding method in which 7,680 × 4,320 pixel images are divided into four images. The encoder LSIs, which are capable of 4K image processing, then encode the divided images in parallel. Video coding methods, including HEVC, generally reduce the amount of information by obtaining the difference between an input image and a coded image (reference image) in accordance with image motion. In this encoder the encoding, which covers the motion across the border of divided images, is achieved by transferring reference images among four chips. This enables high coding efficiency and prevents degradation (Fig. 1).

Data transfer in the encoder also enables other processes to be carried out, including filter de-blocking across image borders and rate control that unifies image quality between divided images. These processes enable high-quality 8K video transmission at 85 Mbps, in contrast to the H.264 standard whose required bitrate is 200-160 Mbps.

A previous example was cited in which 8K encoding was achieved in real time by parallel processing through 4K capable encoder LSIs. However, its coding efficiency and image quality were not good enough because it does not involve data transfer among chips. In another example 8K video was encoded by multiple FPGA based encoder boards involving mutual data transfer. Now, however, higher image quality and more efficient encoding is achieved by using four dedicated encoder LSIs with higher processing performance.

(Fig. 1)
Highly efficient, high-quality encoding enabled by mutual data transfer among chips (Fig. 1)

(2) Smaller size and more economical 8K video encoder (Fig. 2)

In this encoder, 8K real-time encoding is performed on one board on which four HEVC encoder LSIs and peripheral circuit are mounted. Multiple encoder boards have been required previously. The encoder’s size, about 5U (22.25 cm height) at 19 inch rack width makes it significantly smaller and more economical than previous encoders.

(Fig. 2)
Smaller size and more economical 8K video encoder (Fig. 2)

Future Plans

NTT is planning to proceed with trial experiments of ultra-high definition 8K video distribution services including public viewing, ODS, and medical field applications. It is forecast that by 2020 viewers from around the world will be able to watch and enjoy sports events by utilizing these services. NTT will contribute to realize various high-definition and immersive video services by utilizing this technology.