From 6523e2d41d91c1e927ba678fcbc44722a8660474 Mon Sep 17 00:00:00 2001 From: Urvang Joshi Date: Thu, 15 Nov 2012 11:01:41 -0800 Subject: [PATCH] WebP Container: annotate specific sections as experimental Change-Id: If43222cef1c4fc2a8164b5f6ca4e89033379757d --- doc/webp-container-spec.txt | 41 ++++++++++++++++++++----------------- 1 file changed, 22 insertions(+), 19 deletions(-) diff --git a/doc/webp-container-spec.txt b/doc/webp-container-spec.txt index 02fa893d..929d5fa4 100644 --- a/doc/webp-container-spec.txt +++ b/doc/webp-container-spec.txt @@ -13,9 +13,6 @@ end of this file. WebP Container Specification ============================ -_Working Draft, v1.0, 20121109_ - - * TOC placeholder {:toc} @@ -62,6 +59,12 @@ The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 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 ------------------------ @@ -271,17 +274,17 @@ An extended format file consists of: * 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. - * 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 an _animated image_, it consists of multiple frames. More details about frames @@ -322,7 +325,7 @@ Reserved (Rsv): 2 bits : SHOULD be `0`. -ICC profile (I): 1 bit +ICC profile (I): 1 bit _\[status: experimental\]_ : 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 ("alpha"). -EXIF metadata (E): 1 bit +EXIF metadata (E): 1 bit _\[status: experimental\]_ : 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. -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 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. @@ -368,7 +371,7 @@ Future specifications MAY add more fields. ### Chunks -#### Animation +#### Animation _\[status: experimental\]_ 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). -#### Fragments +#### Fragments _\[status: experimental\]_ 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 @@ -641,7 +644,7 @@ The formats of VP8 and VP8L chunks are as described in sections [Simple file format (lossy)](#simple-file-format-lossy) and [Simple file format (lossless)](#simple-file-format-lossless) respectively. -#### Color profile +#### Color profile _\[status: experimental\]_ 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 @@ -663,7 +666,7 @@ See the [ICC Specification][iccspec] for details. If this chunk is not present, sRGB SHOULD be assumed. -#### Metadata +#### Metadata _\[status: experimental\]_ 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 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 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 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 of a fragmented-image and in case of an animated image. The notation