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WebP Container:

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annotate specific sections as experimental

Change-Id: If43222cef1c4fc2a8164b5f6ca4e89033379757d
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Urvang Joshi 2012-11-15 11:01:41 -08:00
parent 4da788da3f
commit 6523e2d41d
1 changed files with 22 additions and 19 deletions
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doc/webp-container-spec.txt
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@ -13,9 +13,6 @@ end of this file.
WebP Container Specification WebP Container Specification
============================ ============================
_Working Draft, v1.0, 20121109_
* TOC placeholder * TOC placeholder
{:toc} {:toc}
@ -62,6 +59,12 @@ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC 2119][]. document are to be interpreted as described in [RFC 2119][].
**Note:** Out of the features mentioned above, lossy compression, lossless
compression and transparency are finalized and are to be considered stable.
On the other hand, metadata, color profile, animation and image fragmentation
are experimental as of now, and are open to discussion, feedback and comments.
The same is indicated using annotation "_status: experimental_" in the relevant
sections of this document.
Terminology & Basics Terminology & Basics
------------------------ ------------------------
@ -271,17 +274,17 @@ 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 color profile. _\[status: experimental\]_
* An optional 'ANIM' chunk with animation control data. * An optional 'ANIM' chunk with animation control data. _\[status: experimental\]_
* Image data. * Image data.
* An optional 'EXIF' chunk with EXIF metadata. * An optional 'EXIF' chunk with EXIF metadata. _\[status: experimental\]_
* An optional 'XMP ' chunk with XMP metadata. * An optional 'XMP ' chunk with XMP metadata. _\[status: experimental\]_
* An optional list of [unknown chunks](#unknown-chunks). * An optional list of [unknown chunks](#unknown-chunks). _\[status: experimental\]_
For a _still image_, the _image data_ consists of a single frame, whereas for For a _still image_, the _image data_ consists of a single frame, whereas for
an _animated image_, it consists of multiple frames. More details about frames an _animated image_, it consists of multiple frames. More details about frames
@ -322,7 +325,7 @@ Reserved (Rsv): 2 bits
: SHOULD be `0`. : SHOULD be `0`.
ICC profile (I): 1 bit ICC profile (I): 1 bit _\[status: experimental\]_
: Set if the file contains an ICC profile. : Set if the file contains an ICC profile.
@ -331,20 +334,20 @@ Alpha (L): 1 bit
: Set if any of the frames of the image contain transparency information : Set if any of the frames of the image contain transparency information
("alpha"). ("alpha").
EXIF metadata (E): 1 bit EXIF metadata (E): 1 bit _\[status: experimental\]_
: Set if the file contains EXIF metadata. : Set if the file contains EXIF metadata.
XMP metadata (X): 1 bit XMP metadata (X): 1 bit _\[status: experimental\]_
: Set if the file contains XMP metadata. : Set if the file contains XMP metadata.
Animation (A): 1 bit Animation (A): 1 bit _\[status: experimental\]_
: 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.
Image Fragmentation (F): 1 bit Image Fragmentation (F): 1 bit _\[status: experimental\]_
: Set if any of the frames in the image are represented by fragments. : Set if any of the frames in the image are represented by fragments.
@ -368,7 +371,7 @@ Future specifications MAY add more fields.
### Chunks ### Chunks
#### Animation #### Animation _\[status: experimental\]_
An animation is controlled by ANIM and ANMF chunks. An animation is controlled by ANIM and ANMF chunks.
@ -475,7 +478,7 @@ Frame Data: _Chunk Size_ - `16` bytes
* An optional list of [unknown chunks](#unknown-chunks). * An optional list of [unknown chunks](#unknown-chunks).
#### Fragments #### Fragments _\[status: experimental\]_
For images that are represented by fragments, this chunk contains data for For images that are represented by fragments, this chunk contains data for
a single fragment. If the _Image Fragmentation Flag_ is not set, then this chunk a single fragment. If the _Image Fragmentation Flag_ is not set, then this chunk
@ -641,7 +644,7 @@ The formats of VP8 and VP8L chunks are as described in sections
[Simple file format (lossy)](#simple-file-format-lossy) [Simple file format (lossy)](#simple-file-format-lossy)
and [Simple file format (lossless)](#simple-file-format-lossless) respectively. and [Simple file format (lossless)](#simple-file-format-lossless) respectively.
#### Color profile #### Color profile _\[status: experimental\]_
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
@ -663,7 +666,7 @@ See the [ICC Specification][iccspec] for details.
If this chunk is not present, sRGB SHOULD be assumed. If this chunk is not present, sRGB SHOULD be assumed.
#### Metadata #### Metadata _\[status: experimental\]_
Metadata can be stored in 'EXIF' or 'XMP ' chunks. Metadata can be stored in 'EXIF' or 'XMP ' chunks.
@ -705,7 +708,7 @@ XMP Metadata: _Chunk Size_ bytes
Additional guidance about handling metadata can be found in the Additional guidance about handling metadata can be found in the
Metadata Working Group's [Guidelines for Handling Metadata][metadata]. Metadata Working Group's [Guidelines for Handling Metadata][metadata].
#### Unknown Chunks #### Unknown Chunks _\[status: experimental\]_
A RIFF chunk (described in [this](#terminology-amp-basics) section) whose _chunk A RIFF chunk (described in [this](#terminology-amp-basics) section) whose _chunk
tag_ is different from any of the chunks described in this document, is tag_ is different from any of the chunks described in this document, is
@ -724,7 +727,7 @@ A file MAY contain unknown chunks:
Readers SHOULD ignore these chunks. Writers SHOULD preserve them in their Readers SHOULD ignore these chunks. Writers SHOULD preserve them in their
original order (unless they specifically intend to modify these chunks). original order (unless they specifically intend to modify these chunks).
### Assembling the Canvas from fragments/frames ### Assembling the Canvas from fragments/frames _\[status: experimental\]_
Here we provide an overview of how a reader should assemble a canvas in case Here we provide an overview of how a reader should assemble a canvas in case
of a fragmented-image and in case of an animated image. The notation of a fragmented-image and in case of an animated image. The notation