Texas Instruments DM365, User Manual

Page: 21 / 131

Introduction
1-9
H.264 Encoder defines in-loop filtering to avoid blocks across the 4x4 block
boundaries. It is the second most computational task of H.264 encoding
process after motion estimation. In-loop filtering is applied on all 4x4 edges
as a post-process and the operations depend upon the edge strength of
the particular edge.
H.264 Encoder applies entropy coding methods to use context based
adaptivity, which in turn improves the coding performance. All the macro
blocks, which belong to a slice, must be encoded in a raster scan order.
Baseline profile uses the Context Adaptive Variable Length Coding
(CAVLC). CAVLC is the stage where transformed and quantized
coefficients are entropy coded using context adaptive table switching
across different symbols. The syntax defined by the H.264 Encoder stores
the information at 4x4 block level.
The following figure depicts the working of the encoder.
Figure 1-4. Block Diagram of H.264 Encoder.
From this point onwards, all references to H.264 Encoder mean H.264
Base/Main/High Profile Encoder only.
Entropy
Coding
Coder
Control
Transform /
Scal / Quant
Deblocking
Filter
Reconstructed
Picture
Intra-frame
Prediction
Motion-
Compensation
Motion-
Estimation
Decoder
Scaling and Inv.
Transform
Control
Data
Quant
Transf coeffs
Output
Picture
Motion
Data
Input
Picture