Add loop filtering section to overview document.
Added section briefly covering loop filtering, cdef and loop
restoration filtering.
Change-Id: I38c994849818fdab113f76de70147ce5a0ccbe2e
diff --git a/doc/dev_guide/av1_encoder.dox b/doc/dev_guide/av1_encoder.dox
index 141673c..b1ae682 100644
--- a/doc/dev_guide/av1_encoder.dox
+++ b/doc/dev_guide/av1_encoder.dox
@@ -79,7 +79,8 @@
For a more detailed overview of AV1's encoding tools and a discussion of some
of the design considerations and hardware constraints that had to be
-accommodated, please refer to *** TODO link to Jingning's AV1 overview paper.
+accommodated, please refer to (TODO REF) <b>A Technical Overview of the AV1
+Standard</b> (TODO add link to Jingning's AV1 overview paper).
Figure 3 provides a slightly expanded but still simplistic view of the
AV1 encoder architecture with blocks that relate to some of the subsequent
@@ -1163,17 +1164,30 @@
See also \ref transform_search for more details.
-\section architecture_loop_filt Loop Filtering
+\section architecture_post_enc_filt Post Encode Loop Filtering
- Add details here.
+AV1 supports three types of post encode <b>in loop</b> filtering to improve
+the quality of the reconstructed video.
-\section architecture_loop_rest Loop Restoration Filtering
+- <b>Deblocking Filter</b> The first of these is a farily traditional boundary
+ deblocking filter that attempts to smooth discontinuities that may occur at
+ the boundaries between blocks. See also \ref in_loop_filter.
- Add details here.
+- <b>CDEF Filter</b> The constrained directional enhancement filter (CDEF)
+ allows the codec to apply a non-linear deringing filter along certain
+ (potentially oblique) directions. A primary filter is applied along the
+ selected direction, whilst a secondary filter is applied at 45° to the
+ primary direction. (See also \ref in_loop_cdef and (TODO REF)
+ <b>A Technical Overview of the AV1 Standard</b> (TODO add link to
+ Jingning's AV1 overview paper).
-\section architecture_cdef CDEF
-
- Add details here.
+- <b>Loop Restoration Filter</b> The loop restoration filter is applied after
+ any prior post filtering stages. It acts on units of either 64 × 64,
+ 128 × 128, or 256 × 256 pixel blocks, refered to as loop restoration units.
+ Each unit can independently select either to bypass filtering, use a Wiener
+ filter, or use a self-guided filter. (See also \ref in_loop_restoration and
+ (TODO REF) <b>A Technical Overview of the AV1 Standard</b> (TODO add link
+ to Jingning's AV1 overview paper).
\section architecture_entropy Entropy Coding
