With necessary sketch explain hierarchical videostructure

Hierarchical video structure, also known as hierarchical video coding, is a type of video coding structure where video frames are organized in a hierarchical manner. This structure is used to improve the efficiency of video coding and to provide scalability in video streaming.

Here's a step-by-step explanation with a sketch:

1. Frame Types: In hierarchical video structure, there are three types of frames: I-frames (Intra-coded), P-frames (Predictive coded), and B-frames (Bi-directionally predictive coded). I-frames are the least compressible but don't require other video frames to decode. P-frames can use data from previous frames to decompress and are more compressible than I-frames. B-frames can use both previous and forward frames for data reference to get encoded and are the most compressible.

2. Hierarchical Structure: The frames are organized in a hierarchical structure, often represented as a tree. At the top level (Level 0), there is an I-frame. This frame is used as a reference by the next level of frames (Level 1), which are typically P-frames. These P-frames are then used as references for the next level (Level 2), which can be either P-frames or B-frames. This structure continues, creating a hierarchy of frames.

3. Sketch: Here's a simple sketch of a 3-level hierarchical video structure:

Level 0: I0------------------------I4------------------------I8
            |                        |                        |
Level 1:   P2------------------------P6------------------------P10
           / \                      / \                      / \
Level 2: B1   B3------------------B5   B7------------------B9   B11

In this sketch, I0, I4, and I8 are I-frames at Level 0. P2, P6, and P10 are P-frames at Level 1 that reference the I-frames. B1, B3, B5, B7, B9, and B11 are B-frames at Level 2 that reference both the I-frames and P-frames.

4. Benefits: The hierarchical video structure allows for more efficient video coding because it reduces the amount of data that needs to be transmitted. It also provides scalability in video streaming, as lower levels of the hierarchy can be dropped to adapt to the available bandwidth.

5. Applications: Hierarchical video structure is used in many video coding standards, including H.264, H.265, and VP9. It's also used in video streaming services like YouTube and Netflix to provide adaptive streaming.