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webp-container-spec: consistently quote FourCCs

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from the AUTH48 portion of the RFC review process

Change-Id: I3aad4b32c95517735e98ffa0120228ee24be6a4d
This commit is contained in:
James Zern 2023-06-02 19:55:46 -07:00
parent 49918af32b
commit f6499943c4
1 changed files with 20 additions and 20 deletions
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40
doc/webp-container-spec.txt
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@ -188,10 +188,10 @@ Simple WebP (lossy) file format:
| WebP file header (12 bytes) | | WebP file header (12 bytes) |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: VP8 chunk : : 'VP8 ' Chunk :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
VP8 chunk: 'VP8 ' Chunk:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
@ -235,10 +235,10 @@ Simple WebP (lossless) file format:
| WebP file header (12 bytes) | | WebP file header (12 bytes) |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: VP8L chunk : : 'VP8L' Chunk :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
VP8L chunk: 'VP8L' Chunk:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
@ -266,17 +266,17 @@ Extended File Format
An extended format file consists of: An extended format file consists of:
* A 'VP8X' chunk with information about features used in the file. * A 'VP8X' Chunk with information about features used in the file.
* An optional 'ICCP' chunk with color profile. * An optional 'ICCP' Chunk with a color profile.
* An optional 'ANIM' chunk with animation control data. * An optional 'ANIM' Chunk with animation control data.
* Image data. * Image data.
* An optional 'EXIF' chunk with Exif metadata. * An optional 'EXIF' Chunk with Exif metadata.
* An optional 'XMP ' chunk with XMP metadata. * An optional 'XMP ' Chunk with XMP metadata.
* An optional list of [unknown chunks](#unknown-chunks). * An optional list of [unknown chunks](#unknown-chunks).
@ -295,7 +295,7 @@ appears in the wrong place, the file is invalid, but readers MAY parse the
file, ignoring the chunks that are out of order. file, ignoring the chunks that are out of order.
**Rationale:** Setting the order of chunks should allow quicker file **Rationale:** Setting the order of chunks should allow quicker file
parsing. For example, if an 'ALPH' chunk does not appear in its required parsing. For example, if an 'ALPH' Chunk does not appear in its required
position, a decoder can choose to stop searching for it. The rule of position, a decoder can choose to stop searching for it. The rule of
ignoring late chunks should make programs that need to do a full search ignoring late chunks should make programs that need to do a full search
give the same results as the ones stopping early. give the same results as the ones stopping early.
@ -343,7 +343,7 @@ XMP metadata (X): 1 bit
Animation (A): 1 bit Animation (A): 1 bit
: Set if this is an animated image. Data in 'ANIM' and 'ANMF' chunks should be : Set if this is an animated image. Data in 'ANIM' and 'ANMF' Chunks should be
used to control the animation. used to control the animation.
Reserved (R): 1 bit Reserved (R): 1 bit
@ -372,9 +372,9 @@ Future specifications may add more fields. Unknown fields MUST be ignored.
#### Animation #### Animation
An animation is controlled by ANIM and ANMF chunks. An animation is controlled by 'ANIM' and 'ANMF' Chunks.
ANIM Chunk: 'ANIM' Chunk:
{:#anim_chunk} {:#anim_chunk}
For an animated image, this chunk contains the _global parameters_ of the For an animated image, this chunk contains the _global parameters_ of the
@ -414,11 +414,11 @@ Loop Count: 16 bits (_uint16_)
: The number of times to loop the animation. If it is `0`, this means : The number of times to loop the animation. If it is `0`, this means
infinitely. infinitely.
This chunk MUST appear if the _Animation_ flag in the VP8X chunk is set. This chunk MUST appear if the _Animation_ flag in the 'VP8X' Chunk is set.
If the _Animation_ flag is not set and this chunk is present, it MUST be If the _Animation_ flag is not set and this chunk is present, it MUST be
ignored. ignored.
ANMF chunk: 'ANMF' Chunk:
For animated images, this chunk contains information about a _single_ frame. For animated images, this chunk contains information about a _single_ frame.
If the _Animation flag_ is not set, then this chunk SHOULD NOT be present. If the _Animation flag_ is not set, then this chunk SHOULD NOT be present.
@ -619,10 +619,10 @@ Alpha bitstream: _Chunk Size_ - `1` bytes
: Encoded alpha bitstream. : Encoded alpha bitstream.
This optional chunk contains encoded alpha data for this frame. A frame This optional chunk contains encoded alpha data for this frame. A frame
containing a 'VP8L' chunk SHOULD NOT contain this chunk. containing a 'VP8L' Chunk SHOULD NOT contain this chunk.
**Rationale**: The transparency information is already part of the 'VP8L' **Rationale**: The transparency information is already part of the 'VP8L'
chunk. Chunk.
The alpha channel data is stored as uncompressed raw data (when the The alpha channel data is stored as uncompressed raw data (when the
compression method is '0') or compressed using the lossless format compression method is '0') or compressed using the lossless format
@ -685,14 +685,14 @@ If this chunk is not present, sRGB SHOULD be assumed.
#### Metadata #### Metadata
Metadata can be stored in 'EXIF' or 'XMP ' chunks. Metadata can be stored in 'EXIF' or 'XMP ' Chunks.
There SHOULD be at most one chunk of each type ('EXIF' and 'XMP '). If there There SHOULD be at most one chunk of each type ('EXIF' and 'XMP '). If there
are more such chunks, readers MAY ignore all except the first one. are more such chunks, readers MAY ignore all except the first one.
The chunks are defined as follows: The chunks are defined as follows:
EXIF chunk: 'EXIF' Chunk:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
@ -707,7 +707,7 @@ Exif Metadata: _Chunk Size_ bytes
: Image metadata in Exif format. : Image metadata in Exif format.
XMP chunk: 'XMP ' Chunk:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1