Cleanup placeholder text and support statement
Change-Id: Icf4d5d30ec160d1ddf8b2dc7832065048e5cd92a
diff --git a/doc/dev_guide/av1_encoder.dox b/doc/dev_guide/av1_encoder.dox
index de563a6..30cb1fe 100644
--- a/doc/dev_guide/av1_encoder.dox
+++ b/doc/dev_guide/av1_encoder.dox
@@ -13,109 +13,7 @@
- \ref in_loop_cdef
- \ref in_loop_restoration
- \ref rate_control
-
- <b>[SAMPLE CONTEXT ONLY - copied from AV1 overview paper]:</b>
-
- In this paper, we present the core coding tools in AV1 that contribute to
- the majority of the 30% reduction in average bitrate compared with the most
- performant libvpx VP9 encoder at the same quality.
-
- \section partition Coding block partition
- VP9 uses a four-way partition tree starting from the 64x64 level down to 4x4
- level, with some additional restrictions for blocks below 8x8 where within an
- 8x8 block all the sub-blocks should have the same reference frame, as shown in
- the top half of Fig. 1, so as to ensure the chroma component can be
- processed in a minimum of 4x4 block unit. Note that partitions designated as
- “R” refer to as recursive in that the same partition tree is repeated at a
- lower scale until we reach the lowest 4x4 level.
-
- \image html partition.png "Fig. 1. Partition tree in VP9 and AV1"
-
- AV1 increases the largest coding block unit to 128x128 and expands the
- partition tree to support 10 possible outcomes to further include 4:1/1:4
- rectangular coding block sizes. Similar to VP9 only the square block is
- allowed for further subdivision. In addition, AV1 adds more flexibility to
- sub-8x8 coding blocks by allowing each unit has their own inter/intra mode and
- reference frame choice. To support such flexibility, it allows the use of 2x2
- inter prediction for chroma component, while retaining the minimum transform
- size as 4x4.
-
- \section intra_prediction Intra prediction
- VP9 supports 10 intra prediction modes, including eight directional modes
- corresponding to angles from 45 to 207 degrees, and two non-directional
- predictors: DC and true motion (TM) mode. In AV1, the potential of an intra
- coder is further explored in various ways: the granularity of directional
- extrapolation is upgraded, non-directional predictors are enriched by taking
- into account gradients and evolving correlations, coherence of luma and
- chroma signals is exploited, and tools are developed particularly for
- artificial content.
-
- -# Enhanced directional intra prediction\n
- To exploit more varieties of spatial redundancy in directional textures, in
- AV1, directional intra modes are extended to an angle set with finer
- granularity for blocks larger than 8x8. The original eight angles are made
- nominal angles, based on which fine angle variations in a step size of 3
- degrees are introduced, i.e. the prediction angle is presented by a nominal
- intra angle plus an angle delta, which is -3x3 multiples of the step size. To
- implement directional prediction modes in AV1 via a generic way, the 48
- extension modes are realized by a unified directional predictor that links
- each pixel to a reference sub-pixel location in the edge and interpolates
- the reference pixel by a 2-tap bilinear filter. In total, there are 56
- directional intra modes supported in AV1.
-
- Another enhancement for directional intra prediction in AV1 is that, a low-
- pass filter is applied to the reference pixel values before they are used
- to predict the target block. The filter strength is pre-defined based on
- the prediction angle and block size.
-
- -# New non-directional smooth intra predictors\n
- VP9 has two non-directional intra prediction modes: DC_PRED and TM_PRED.
- AV1 expands on this by adding three new prediction modes: SMOOTH_PRED,
- SMOOTH_V_PRED, and SMOOTH_H_PRED. Also a fourth new prediction mode
- PAETH_PRED replaces the existing mode TM_PRED. The new modes work as
- follows:
-
- - <b>SMOOTH_PRED</b>: Useful for predicting blocks that have a smooth
- gradient.
-
- - <b>SMOOTH_V_PRED</b>: Similar to SMOOTH_PRED, but uses quadratic
- interpolation only in the vertical direction.
-
- - <b>SMOOTH_H_PRED</b>: Similar to SMOOTH_PRED, but uses quadratic
- interpolation only in the horizontal direction.
-
- - <b>PAETH_PRED</b>: Calculate \f$base=left + top -top\_left\f$. Then
- predict this pixel as left, top, or top-left pixel depending on which of them
- is closest to “base”.
-
- \section inter_prediction Inter prediction
- Motion compensation is an essential module in video coding. AV1 has a more
- powerful inter coder, which largely extends the pool of reference frames and
- motion vectors, breaks the limitation of block-based translational prediction,
- also enhances compound prediction by using highly adaptable weighting
- algorithms as well as sources.
-
- -# Extended reference frames\n
- AV1 extends the number of references for each frame from 3 to 7. Figure 4
- demonstrates the multi-layer structure of a golden-frame group, in which an
- adaptive number of frames share the same GOLDEN and ALTREF frames. BWDREF
- is a look-ahead frame directly coded without applying temporal filtering,
- thus more applicable as a backward reference in a relatively shorter
- distance. ALTREF2 serves as an intermediate filtered future reference
- between GOLDEN and ALTREF.
-
- \image html gf_group.png "Fig. 4. Example of multi-layer structure of a golden-frame group"
-
- -# Advanced compound prediction\n
- A collection of new compound prediction tools is developed for AV1 to make
- its inter coder more versatile. In this section, any compound prediction
- operation can be generalized for a pixel \f$(i,j)\f$ as:
- \f$p_f(i,j)=m(i,j)p_1(i,j)+(1-m(i,j))p_2(i,j)\f$, where \f$p_1\f$ and
- \f$p_2\f$ are two predictors, and \f$p_f\f$ is the final joint prediction,
- with the weighting coefficients \f$m(i,j)\f$ in \f$[0,1]\f$ that are
- designed for different use cases and can be easily generated from predefined
- tables.
-*/
+ */
/*!\defgroup encoder_algo Encoder Algorithm
*
diff --git a/mainpage.dox b/mainpage.dox
index 7e10515..10924ac 100644
--- a/mainpage.dox
+++ b/mainpage.dox
@@ -50,10 +50,9 @@
<br>
\section main_support Support Options & FAQ
- The AOMedia project is an open source project supported by its community. For
- questions about this SDK, please mail the apps-devel@webmproject.org list.
- To contribute, see http://www.webmproject.org/code/contribute and mail
- codec-devel@webmproject.org.
+ The AOMedia project is an open source project supported by its community.
+ For questions about this SDK or for help, please visit http://aomedia.org/
+ and email the aomediacodec@jointdevelopment.kavi.com list.
*/
/*!\page changelog CHANGELOG
