If ReadBits(0) == 0, the value of max_symbol is set to the alphabet size
for each symbol type.
See vp8l_dec.c, ReadHuffmanCode(), which passes alphabet_size to
ReadHuffmanCodeLengths() as num_symbols, and ReadHuffmanCodeLengths()
then sets max_symbol to that.
Bug: webp:611
Change-Id: I662bd1d7f372e7f2e9c71cc86f87aefd02f36647
Make Entropy Image and Interpretation of Meta Prefix Codes their own
section for ease of reference.
Bug: webp:611
Change-Id: I2dba7b4efd02d8bb250810ebff42ac1687262804
follow up to:
29c9f2d4 webp-lossless-bitstream-spec: minor wording updates
Universally use 'transform' over 'transformation'. The doc generally
uses 'transform' to talk about the individual transforms themselves as
well as their related data.
Bug: webp:611
Change-Id: I097701873bbc440bd399ab5440a914a14f7c62f6
The last use of #decoding-the-code-lengths was removed in:
86f94ee0 Update lossless spec with Huffman codes.
Also remove the redundant section header associated with it.
Bug: webp:611
Change-Id: I7f6bb1a1b75255324f185f4591313d9e6d49d1e9
Remove the ambiguous 'should' which in other contexts might result in
questions as to whether it is a SHOULD or a MUST.
Change-Id: I9b396187ebde5ea5a0dbaf42daee6acf541258cd
Within the 'Entropy image' subsection, its clear this is what is being
described in the following paragraphs. Remove 'as described below' from
the first sentence.
Bug: webp:611
Change-Id: I365d69c8f6963cd826849ebdd96e46206d38b55d
Move this to the top-level of the "Details" section as prefix codes are
discussed in both "Decoding and Building the Prefix Codes" and "Decoding
of Meta Prefix Codes"
Bug: webp:611
Change-Id: Ide2dfedf081d6c94122ac16ecded968ed760f90c
in the Transformations section describing decoding of the transform
data followed by the image data. The section numbers were adjusted by 1
in:
337cf69f webp-lossless-bitstream-spec: mv Nomenclature after Intro
Bug: webp:611
Change-Id: I4eede0d068fabdef51a140a0268436ab6629e8bb
Give some examples of repetition and binary value notation to limit the
need to follow the ABNF reference.
Bug: webp:611
Change-Id: I5b5a7632f011e1523b4a528653fe3630afba3e3e
in 6.2.3 Decoding Entropy-Coded Image Data.
The copying of distance code pixels cause some confusion during the
AUTH48 portion of the RFC review process.
Bug: webp:611
Change-Id: I78f547ae10c95f180355a4c93ec6d48acdc09141
Mostly grammatical and addition/subtraction of commas from the AUTH48
portion of the RFC review process.
The serial comma changes are based on the Chicago Manual of Style
(CMOS), 17th edition.
Bug: webp:611
Change-Id: I5ae2d1cc0196009dbf3a4c2195cc73c2ef809b49
Reference the section by number, rather than 'this section'. Fixes a
lint warning:
Style notice: Write unique, descriptive link text that makes sense
without the surrounding text. Don't use phrases such as this document,
this article, or click here.
https://developers.google.com/style/link-text?hl=en#write-link-text
Change-Id: Iab33e4980528dddb5eed4404d25a4a746705131a
remove AMENDED-notes (the last functional spec change to match with the
implementation is from 2014, other amendments are clarifications)
Bug: webp:581
Change-Id: Ic47739be0fd5a975fd734d6813567ca615304f1d
Have this match simple-prefix-code and redirect to "Normal Code Length
Code" as the added indirection to 'code-length-code' and the undefined
'encoded-code-lengths' doesn't add much.
spotted by thakis@
Change-Id: Icd6b64a47c4e0001e93271d9ae5585be4a6d5906
- add missing '(' in DIV_ROUND_UP
- in 6.2.2, rename 'pos' variable reference to match definition
('position')
spotted by thakis@
Change-Id: Ida3ed281c2c753ebbb0e1eb3c4ed04dadc79ca24
for fixes to the distance_map pseudo-code, the inverse color transform
description and the num_code_lengths check.
Bug: webp:448
Bug: webp:551
Change-Id: Id7e791b97704dd64bb9519657ce48b92cb457ae4
The prose describing the process was missed in:
44dd765d webp-lossless-bitstream-spec: fix ColorTransform impl
Bug: webp:448
Bug: webp:551
Change-Id: If5fb95103ffedeed113e3ad62510f3a19bfd280e
in the 'Normal Code Length Code' description the number of valid code
lengths is 19, not 18.
Bug: webp:448
Bug: webp:551
Change-Id: Id929604e1d771cb09b2d0ac617e83f21077f21de
'zero alpha pixels' was a bit hard to parse; replace this with something
more explicit
Bug: webp:448
Change-Id: Ifc8c93af5520ffdafc58e3fc311dfb4cb19626e9
this is similar to an earlier change for most of the code examples:
7a0a9935 doc/*.txt: restrict code to 69 columns
some renderers may limit output to 72 and use a 3 space indent; this
avoids overflowing into the margin
Bug: webp:448
Change-Id: I2e8d66f598889c7bd824e911ea01fd70f98a4130
The distance code read from the bitstream is reduced by 1 before doing
the lookup. The prose describing the lookup was correct, the pseudocode
failed to subtract 1 and used x/y instead of xi/yi from the lookup.
Bug: webp:448
Change-Id: I152477b888c26a0473a35373d3d331fddd14237f
this has a better canonical reference [1] and is preferred in IETF docs
[1] https://www.rfc-editor.org/rfc/rfc5234
Bug: webp:448
Change-Id: I3f0bd34d3ca4c62b255d5d6cbae0c55e2940dfb5
some renderers may limit output to 72 and use a 3 space indent; this
avoids overflowing into the margin
Change-Id: Iaf4e8b71be27ef00fccd1d82b79bf96c01040f10
... since no guarantee of Huffman coding can be introduced at decoding
time and encoding didn't actually use Huffman coding in the first place
Bug: webp:551
Change-Id: I400466bb3b4a1d5506353eb3f287d658603164ee
for recent changes to color transform, simple code length code, image
structure and details of decoding prefix codes
Bug: webp:551
Change-Id: I36a4d1ee3e25b8a56f5d926f4770374ace99bc2f
