Nokia Explains Random Access in Video Coding Standards

Nokia Oyj has provided an in-depth explanation of how random access functions within modern video coding standards such as AVC, HEVC, and VVC. This technology is fundamental to enabling smooth video experiences, including features like fast-forwarding, channel surfing, and joining video conferences mid-stream.

Random access allows video decoding without requiring the playback of all preceding content. This is achieved through specific frame types, including Instantaneous Decoding Refresh (IDR) frames and Clean Random Access (CRA) frames. An IDR frame is self-contained, while a CRA frame allows for greater compression efficiency without sacrificing quality, as it can be followed by frames that precede it in display order.

Nokia highlights that implementing random access can come at the cost of compression efficiency because it doesn't leverage the temporal correlation between video frames. Recent standards aim to balance this challenge, with CRA frames potentially reducing bitrate by up to nine percent compared to IDR frames.

The company also discusses Gradual Decoding Refresh (GDR), a method where frame content is refreshed over multiple frames. GDR is particularly suited for low-latency applications such as cloud gaming and 5G networks, as it helps avoid bitrate fluctuations and enables low end-to-end latency.

These advancements, according to Nokia, are essential for efficiently supporting the ever-increasing consumption of video content and new applications across various network conditions.