2.360 度视频的流式传输技术

Streaming techniques for 360-degree videos have evolved from full-view equal quality (viewport-independent) methods to more sophisticated approaches like viewport-only equal quality or full-view non-equal quality (viewport-dependent) modes, as well as tile-based strategies. Unlike regular video encoding, a 360-degree video is encoded to capture a complete omnidirectional scene.

To provide adaptive 360-degree video streaming, the Dynamic Adaptive Streaming over HTTP (DASH) framework is commonly used for bitrate adaptation. This allows the video streaming system to dynamically adjust the quality of the video based on the viewer’s network conditions and device capabilities.

Let’s delve a bit deeper into these concepts:

1. Evolution of 360-Degree Video Streaming:

   • Full-View Equal Quality (Viewport-Independent): In the early stages of 360-degree video streaming, videos were encoded with equal quality across the entire sphere, regardless of the viewer’s perspective. This approach consumes a lot of bandwidth, as all parts of the video are encoded at the same quality.

   • Viewport-Only Equal Quality (Viewport-Dependent): As technology advanced, streaming methods began to prioritize encoding the portion of the video currently in the viewer’s field of view at a higher quality. The quality of the non-viewable areas could be reduced, saving bandwidth and improving efficiency.

   • Full-View Non-Equal Quality (Viewport-Dependent): Some methods focus on encoding the entire 360-degree video but allocate more bits to the visible parts while reducing the quality of the non-visible areas, offering a compromise between quality and bandwidth efficiency.

   • Tile-Based Strategies: A more recent development involves dividing the 360-degree video into tiles, where each tile can be encoded separately. The level of detail can be adjusted for each tile based on the viewer’s perspective. This approach enhances streaming efficiency by concentrating data where the viewer is looking.

2. Dynamic Adaptive Streaming over HTTP (DASH):

   • DASH is a streaming protocol that allows for adaptive bitrate streaming. It segments video content into smaller, discrete files and offers multiple bitrates and resolutions for each segment. These segments are then made available over HTTP. When a viewer watches a video using DASH, their device continuously monitors the network conditions and device capabilities.

   • DASH enables seamless bitrate adaptation during playback. If network conditions degrade, DASH can switch to a lower quality bitrate, ensuring uninterrupted viewing. Conversely, if conditions improve, DASH can increase the quality to provide a better viewing experience.

   • For 360-degree video streaming, DASH can be particularly valuable, as it allows the system to dynamically adjust the quality of the video based on the viewer’s changing perspective and network conditions. It’s a key technology for optimizing the delivery of 360-degree content to viewers with varying devices and network connections.

In summary, the evolution of 360-degree video streaming has involved various techniques to optimize bandwidth usage while maintaining video quality. Dynamic Adaptive Streaming over HTTP (DASH) is a widely adopted framework that enables adaptive streaming, making it possible to tailor the viewing experience to the viewer’s device and network conditions. This is especially valuable in the context of 360-degree video, where the viewer’s perspective is constantly changing, and bandwidth efficiency is crucial.