AOMediaCodec / av1-spec

….6.3

Bump jekyll from 3.3.1 to 3.6.3

Bumps [jekyll](https://github.com/jekyll/jekyll) from 3.3.1 to 3.6.3.
- [Release notes](https://github.com/jekyll/jekyll/releases)
- [Changelog](https://github.com/jekyll/jekyll/blob/master/History.markdown)
- [Commits](jekyll/jekyll@v3.3.1...v3.6.3)

Signed-off-by: dependabot[bot] <support@github.com>

…ash-4.17.19

Bump lodash from 4.17.11 to 4.17.19

Bumps [lodash](https://github.com/lodash/lodash) from 4.17.11 to 4.17.19.
- [Release notes](https://github.com/lodash/lodash/releases)
- [Commits](lodash/lodash@4.17.11...4.17.19)

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BUG=aomedia:2372

Add a definition of the term "tier" to Section 2.

BUG=aomedia:2380

RTC SG clarifications on high-level syntax

OBU ordering clarification

The decoder model tracks which reference frames can be freed.
This correction ensures that all relevant frames are freed instead of just checking the first one. 

BUG=aomedia:2370

Change 1/0 values in layer-specific table entries to Y/N. Changed T35 layer-specific info from application-specific to payload-specific.

[Editorial] remove mask blend 4:4:0 condition

subsampling_x = 0 and subsampling_y = 1 corresponds to 4:4:0, this is a left over from vp9.
https://crbug.com/aomedia/2399

Apply only to frame-related OBUs.

https://crbug.com/aomedia/2295

BUG=aomedia:2328

"n-bit" implies a fixed length, so it contradicts "Variable length" in the description. Also, the variable 'n' does not appear in the description of uvlc().

Clarifications on the use of OBU extension header in various OBU types as well as the scope of metadata OBUs.

VP9 allowed information to be used from the tile above.
This has been corrected in AV1 so the note is no longer needed.

The two for loops in the reference frame update process do not have any dependency between them and therefore can be merged.

Add PATENTS file, as Markdown text

* Create file and add text from https://aomedia.org/license/patent-license/
* Convert fancy glyphs to plain
* Markdown-ify text

Do not capitalize the syntax element name "reference_select", even when it appears at the beginning of a sentence. This is the style used in the spec.

setup_past_independence() does not need to set GmType[ ref ] to IDENTITY.

See https://crbug.com/aomedia/2301. Although it is harmless to set a field unnecessarily, it may mislead someone who is trying to analyze the spec. I propose we remove this line to avoid potential misunderstanding during spec analysis.

BUG=aomedia:2301

Make it clear that the segmentation map specifies a segment affiliation for each 4x4 block in the frame.

BUG=aomedia:2314

The tile width and area limits were expressed using "less".  
This should have used less than or equal to allow the maximum tile dimensions to be reached.

Change "segment map" to "segmentation map" (the prevalent form used in the spec) for consistency.