Chromium Blog: Chrome 90 Beta: AV1 Encoder for WebRTC, New Origin Trials, and More

Chromium Blog

News and developments from the open source browser project

Chrome 90 Beta: AV1 Encoder for WebRTC, New Origin Trials, and More

jueves, 11 de marzo de 2021

Unless otherwise noted, changes described below apply to the newest Chrome beta channel release for Android, Chrome OS, Linux, macOS, and Windows. Learn more about the features listed here through the provided links or from the list on ChromeStatus.com. Chrome 90 is beta as of March 11, 2021.AV1 EncoderAn AV1 encoder is shipping in Chrome desktop that is specifically optimized for video conferencing with WebRTC integration. The benefits of AV1 include:

Better compression efficiency than other types of video encoding, reducing bandwidth consumption and improve visual quality

Enabling video for users on very low bandwidth networks (offering video at 30kbps and lower)

Significant screen sharing efficiency improvements over VP9 and other codecs.

This is an important addition to WebRTC especially since it recently became an official W3C and IETF standard.Origin TrialsThis version of Chrome introduces the origin trials described below. Origin trials allow you to try new features and give feedback on usability, practicality, and effectiveness to the web standards community. To register for any of the origin trials currently supported in Chrome, including the ones described below, visit the Chrome Origin Trials dashboard. To learn more about origin trials in Chrome, visit the Origin Trials Guide for Web Developers. Microsoft Edge runs its own origin trials separate from Chrome. To learn more, see the Microsoft Edge Origin Trials Developer Console. New Origin TrialsgetCurrentBrowsingContextMedia()The mediaDevices.getCurrentBrowsingContextMedia() method allows capturing a MediaStream with the current tab's video (and potentially audio), similar to getDisplayMedia(). Unlike getDisplayMedia(), calling this new method will eventually present the user with a simple accept/reject dialog box. If the user accepts, the current tab is captured. However, this will require some additional security measures which are still being finalized. Until then, or if the call is made with these measures absent, a dialog is displayed to the user that allows the selection of any source, but highlights the option of the current tab (whereas normally getDisplayMedia highlights the option of entire-screen).MediaStreamTrack Insertable Streams (a.k.a. Breakout Box)An API for manipulating raw media carried by MediaStreamTracks such as the output of a camera, microphone, screen capture, or the decoder part of a codec and the input to the decoder part of a codec. It uses WebCodecs interfaces to represent raw media frames and exposes them using streams, similar to the way the WebRTC Insertable Streams API exposes encoded data from RTCPeerConnections. This is intended to support use cases such as:

Funny Hats: Refers to manipulation of media either before encoding and after decoding to provide effects such as background removal, funny hats, voice effects.

Machine Learning: Refers to applications such as real-time object identification/annotation.

This origin trial is expected to run through Chrome 92.Subresource Loading with Web BundlesSubresource loading with Web Bundles provides a new approach to loading a large number of resources efficiently using a format that allows multiple resources to be bundled., e.g. Web Bundles.The output of JavaScript bundlers (e.g. webpack) doesn't interact well with browsers. They are good tools but:

Their output can't interact with the HTTP cache at any finer grain than the bundle itself (not solved with this origin trial). This can make them incompatible with new requirements like dynamic bundling (e.g. small edit with tree shaking could invalidate everything).

They force compilation and execution to wait until all bytes have arrived. Ideally loading multiple subresources should be able to utilize full streaming and parallelization, but that's not possible if all resources are bundled as one javascript. (This origin trial allows compilation to proceed in parallel. For JavaScript modules, execution still needs to wait for the entire tree due to the current deterministic execution model).

They can require non-JS resources like stylesheets and images to be encoded as JS strings, which forces them to be parsed twice and can increase their size. This origin trial allows those resources to be loaded in their original form.

This origin trial also allows a bundle to include the source for an opaque-origin iframe as urn:uuid: resources. The scheme for these resources is expected to change in Chrome 91.This origin trial is expected to run through Chrome 92.WebAssembly Exception HandlingWebAssembly now provides exception handling support. Exception handling allows code to break control flow when an exception is thrown. The exception can be any that is known by the WebAssembly module, or it may be an unknown exception that was thrown by a called imported function. This origin trial is expected to run through Chrome 94.Completed Origin TrialsThe following features, previously in a Chrome origin trial, are now enabled by default.WebXR AR Lighting EstimationLighting estimation allows sites to query for estimates of the environmental lighting conditions within WebXR sessions. This exposes both spherical harmonics representing the ambient lighting, as well as a cubemap texture representing "reflections". Adding Lighting Estimation can make your models feel more natural and like they "fit" better with the user's environment.Other Features in this ReleaseCSSaspect-ratio InterpolationThe aspect-ratio property allows for automatically computing the other dimension if only one of width or height is specified on any element. This property was originally launched as non-interpolable (meaning that it would snap to the target value) when animated. This feature provides smooth interpolation from one aspect ratio to another.Custom State Pseudo ClassesCustom elements now expose their states via the state CSS pseudo class. Built-in elements have states that can change over time depending on user interaction and other factors, which are exposed to web authors through pseudo classes. For example, some form controls have the "invalid" state, which is exposed through the :invalid pseudo class. Since custom elements also have states it makes sense to expose their states in a manner similar to built-in elements.Implement 'auto' value for appearance and -webkit-appearanceThe default values of CSS property appearance and -webkit-appearance for the following form controls are changed to 'auto'.

<input type=color> and <select>

Android only: <input type=date>, <input type=datetime-local>, <input type=month>, <input type=time>, and <input type=week>

Note that the default rendering of these controls are not changed.overflow: clip PropertyThe clip value for overflow results in a box's content being clipped to the box's overflow clip edge. In addition, no scrolling interface is provided, and the content cannot be scrolled by the user or programmatically. Additionally the box is not considered a scroll container, and does not start a new formatting context. As a result, this value has better performance than overflow: hidden.overflow-clip-margin PropertyThe overflow-clip-margin property enables specifying how far outside the bounds an element is allowed to paint before being clipped. It also allows the developer to expand the clip border. This is particularly useful for cases where there is ink overflow that should be visible.Permissions-Policy HeaderThe Permissions-Policy HTTP header replaces the existing Feature-Policy header for controlling delegation of permissions and powerful features. The header allows sites to more tightly restrict which origins can be granted access to features.The Feature Policy API, introduced in Chrome 74, was recently renamed to "Permissions Policy", and the HTTP header has been renamed along with it. At the same time, the community has settled on a new syntax, based on structured field values for HTTP.Protect application/x-protobuffer via Cross-Origin-Read-Blocking Protect application/x-protobuffer from speculative execution attacks by adding it to the list of never sniffed MIME types used by Cross-Origin-Read-Blocking. application/x-protobuf is already protected as a never sniffed mime type. application/x-protobuffer is another commonly used MIME type that is defined as an "ALT_CONTENT_TYPE" by the protobuf library. Seeking Past the End of a File in the File System Access APIWhen data is passed to FileSystemWritableFileStream.write() that would extend past the end of the file, the file is now extended by writing 0x00 (NUL). This enables creating sparse files and greatly simplifies saving content to a file when the data to be written is received out of order.
Without this functionality, applications that receive file contents out of order (for example, BiTtorrent downloads) would have to manually resize the file either ahead of time or when needed during writing.StaticRange ConstructorCurrently, Range is the only constructible range type available to web authors. However, Range objects are "live" and maintaining them can be expensive. For every tree change, all affected Range objects need to be updated. The new StaticRange objects are not live and represent a lightweight range type that is not subject to the same maintenance cost as Range. Making StaticRange constructible allows web authors to use them for ranges that do not need to be updated on every DOM tree change.Support Specifying Width and Height on <source> Elements for <picture>The <source> element now supports width and height properties when used inside a <picture> element. This allows Chrome to compute an aspect ratio for <picture> elements. This matches similar behavior for <img>, <canvas> and <video> elements.WebAudio: OscillatorOptions.periodicWave is Not NullableIt is no longer possible to set periodicWave to null when creating a new OscillatorNode object. This value is set on the options object passed to the OscillatorNode() constructor. The WebAudio spec doesn't allow setting this value to null. Chrome now matches both the spec and Firefox. JavaScriptThis version of Chrome incorporates version 9.0 of the V8 JavaScript engine. It specifically includes the changes listed below. You can find a complete list of recent features in the V8 release notes.Relative Indexing Method for Array, String, and TypedArraysArray, String, and TypedArray now support the at() method, which supports relative indexing with negative numbers. For example, the code below returns the last item in the given array.let arr = [1,2,3,4]; arr.at(-1); Deprecations, and RemovalsThis version of Chrome introduces the deprecations and removals listed below. Visit ChromeStatus.com for lists of current deprecations and previous removals.Remove Content Security Policy Directive 'plugin-types'The 'plugin-types' directive allows developers to restrict which types of plugin can be loaded via <embed> or <object> html elements. This allowed developers to block Flash in their pages. Since Flash support has been discontinued, there is no longer any need for this policy directive.Remove WebRTC RTP Data ChannelsChrome has removed support for the non-standard RTP data channels in WebRTC. Users should use the standard SCTP-based data channels instead.Return Empty for navigator.plugins and navigator.mimeTypesChrome now returns empty for navigator.plugins and navigator.mimeTypes. With the removal of Flash, there is no longer the need to return anything for these properties.