Block Structures and Parallelism Features in HEVC - High Efficiency Video Coding (HEVC) - page 51

Mode-, Quadtree-,
Motion- and
Filter Information

Encoder Control

Coding Quadtree
with
Coding Blocks

Residual Quadtree
with
Transform Blocks

Output

CABAC
Entropy
Coding

Transform,
Scaling &
Quantization

010110...

- Bitstream

Quantized
Transform
Coefficients

Decoder

Subdivision into
Coding Tree Blocks

Scaling &
Inverse Transform

Intra-Picture
Prediction

In-Loop Filter

Inter-Picture
Prediction

Output
Video Signal

Input

Prediction Blocks

Video Signal

Motion Estimation

Decoded Picture Buffer

Fig. 3.1 Block diagram of an HEVC encoder with built-in decoder ( gray shaded )

new features of tiles and wavefront parallel processing (WPP). Also, it is described
how these picture partitioning features can be used together with the concept of
slice segments for improved bitstream access. Section 3.3.3 deals with the same
combination of tools but from the different perspective of support for ultra-low delay
applications. Finally, in Sect. 3.3.4 , the assets and drawbacks of tiles and WPP are
discussed. The whole chapter is concluded in Sect. 3.4 .

3.2 Block Partitioning for Prediction and Transform Coding

All ITU-T and ISO/IEC video coding standards since H.261 [ 14 ] follow the
approach of block-based hybrid video coding, as it was already briefly discussed
above and illustrated in Fig. 3.1 . One significant difference between the different
generations of video coding standards is that they provide different sets of coding
modes for a block of samples. On the one hand, the selected coding mode determines
whether the block of samples is predicted using intra-picture or inter-picture
prediction. On the other hand, it can also determine the subdivision of a given block
into subblocks used for prediction and/or transform coding. Blocks that are used for
prediction are typically additionally associated with prediction parameters, such as
motion vectors or intra prediction modes.