I need to request a further extension of this origin trial, to end in M104 instead of the current end of 103.
While I've just sent the intent-to-ship for this feature <https://groups.google.com/a/chromium.org/g/blink-dev/c/FRY3F1v6Two> (with target milestone 105), I have just received a request from another major web developer for the origin trial to be extended into 104. The full implementation and stabilization of this feature didn't land until early in the 105 milestone due to some API changes requested by participants in the media workgroup discussions of this feature. While these changes in 105 are not expected to be part of the origin trial, the bulk of the MSE-in-Workers implementation remains usable via the origin-trial-feature "MediaSourceInWorkers" using the older API shape. The primary change in the API shape is to use a MediaSourceHandle for attaching a worker MediaSource instead of a MediaSource object URL. Extending the OT into 104 will enable experimentation as requested by the web developer. Please review this request and advise on next steps. Note, this is not intended to replace the intent to ship in 105 for this feature, but instead to let the feature continue to be experimented with in 104. Thank you, Matt On Wed, Feb 23, 2022 at 9:06 AM Matthew Wolenetz <wolen...@chromium.org> wrote: > Thank you. The results so far have been very encouraging, so I expect no > further extension would be necessary beyond 103. > > On Wed, Feb 23, 2022 at 5:18 AM Yoav Weiss <yoavwe...@chromium.org> wrote: > >> LGTM to continue experimenting till M103. Note that this will bring the >> OT to 9 releases, so it'd be good to wrap up experimentation by this >> extension's end. >> >> On Wednesday, February 16, 2022 at 11:03:08 PM UTC+1 Matthew Wolenetz >> wrote: >> >>> Hello blink-dev, >>> >>> We'd like to ask for an extension to our Origin Trial, from M99 to M103. >>> >>> There are two reasons extension is necessary: >>> >>> 1) A breaking error discovered in the middle of the trial (see >>> https://crbug.com/1268614) caused participation to drop before the 2021 >>> holiday period. While the fix landed by early 2022 and at least one >>> participant has reported excellent improvement in metrics in their >>> experiment since then, further stabilization is desired. >>> >>> 2) An API change for this feature (using srcObject for MSE-in-Workers >>> attachments instead of baking in objectURL attachment further) was agreed >>> with the media workgroup last September [1] following the previous >>> objectURL-based attachment design getting more recent feedback [2], and I'm >>> working on getting that into both the feature spec and Chromium's >>> experimental implementation currently for rapid experimentation during the >>> extended trial. >>> >>> [1] https://www.w3.org/2021/09/14-mediawg-minutes.html >>> [2] https://github.com/mozilla/standards-positions/issues/547 >>> >>> >>> Please find the Chrome status template, below: >>> >>> >>> Contact emailswolen...@chromium.org >>> >>> Explainer >>> https://github.com/wicg/media-source/blob/mse-in-workers-using-handle/mse-in-workers-using-handle-explainer.md >>> >>> Specificationhttps://github.com/w3c/media-source/pull/282 >>> >>> Summary >>> >>> Enable Media Source Extensions (MSE) API usage from DedicatedWorker >>> contexts to enable improved performance of buffering media for playback by >>> an HTMLMediaElement on the main Window context. By creating a MediaSource >>> object on a DedicatedWorker context, an application may then create an >>> ObjectURL for it and postMessage that URL to the main thread for use in >>> attaching to an HTMLMediaElement. The context that created the MediaSource >>> object may then use it to buffer media. >>> >>> >>> Blink componentBlink>Media >>> <https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EMedia> >>> >>> Search tagsMSE <https://chromestatus.com/features#tags:MSE>, MediaSource >>> <https://chromestatus.com/features#tags:MediaSource>, >>> MediaSourceExtensions >>> <https://chromestatus.com/features#tags:MediaSourceExtensions> >>> >>> TAG reviewhttps://github.com/w3ctag/design-reviews/issues/656 >>> >>> TAG review statusIssues addressed >>> >>> Risks >>> >>> >>> Interoperability and Compatibility >>> >>> Main interoperability risk is that other browsers may not implement it. >>> Compatibility risk is mitigated by unchanged same-thread MSE API support >>> and proactive feature-detectability of MSE-in-Workers with a new >>> canConstructInDedicatedWorker attribute on the MediaSource interface. >>> >>> >>> Gecko: No signal ( >>> https://github.com/mozilla/standards-positions/issues/547) >>> >>> WebKit: No signal ( >>> https://lists.webkit.org/pipermail/webkit-dev/2021-June/031916.html) >>> >>> Web developers: No signals >>> >>> Other signals: >>> >>> Ergonomics >>> >>> DedicatedWorker, WorkerGlobalScope and postMessage/onmessage >>> availability is integral to using this feature. >>> >>> >>> Activation >>> >>> The primary risk is the potential difficulty in refactoring existing MSE >>> web applications to (conditionally, depending on browser support) perform >>> buffering in a different execution context from the Window context that >>> hosts the DOM and the media element. The benefit of potentially improved >>> buffering performance by offloading the MSE API usage to a worker context >>> provides motivation to overcome this challenge. >>> >>> >>> Security >>> >>> Unpredictability of racing context destruction of either the main thread >>> hosting the media element (and owning the underlying MSE media demuxer and >>> player) or the dedicated worker thread hosting the interface to the MSE >>> demuxer when using MSE from a worker context motivated careful design of a >>> refcounted, outside-of-Oilpan, attachment abstraction to ensure safety of >>> operations using locks and having a lifetime that exceeds those execution >>> contexts. Preventing use-after-free and similar was a primary complexity of >>> implementation and a focus area of added tests. >>> >>> >>> Goals for experimentation >>> >>> * Obtain developer feedback on API ergonomics and implementation >>> stability. * Increase confidence in benefits of feature (exposing and >>> enabling MSE usage from DedicatedWorker contexts) to support its >>> standardization. >>> >>> >>> Reason this experiment is being extended >>> >>> There are two reasons extension is necessary: 1) A breaking error >>> discovered in the middle of the trial (see https://crbug.com/1268614) >>> caused participation to drop before the 2021 holiday period. While the fix >>> landed by early 2022 and at least one participant has reported excellent >>> improvement in metrics in their experiment since then, further >>> stabilization is desired. 2) An API change for this feature (using >>> srcObject for MSE-in-Workers attachments instead of baking in objectURL >>> attachment further) was agreed with the media workgroup last September [1] >>> following the previous objectURL-based attachment design getting more >>> recent feedback [2], and I'm working on getting that into both the feature >>> spec and Chromium's experimental implementation currently for rapid >>> experimentation during the extended trial. [1] >>> https://www.w3.org/2021/09/14-mediawg-minutes.html [2] >>> https://github.com/mozilla/standards-positions/issues/547 >>> >>> >>> Ongoing technical constraints >>> >>> >>> >>> Debuggability >>> >>> Feature consists of exposing existing interfaces also on a >>> DedicatedWorker, and addition of a WebIDL method for proactively detecting >>> support for this feature, and are covered by basic tooling. >>> >>> >>> Will this feature be supported on all six Blink platforms (Windows, Mac, >>> Linux, Chrome OS, Android, and Android WebView)?Yes >>> >>> MSE and DedicatedWorker already exist on all six Blink platforms. This >>> feature lets MSE work from DedicatedWorker contexts. >>> >>> >>> Is this feature fully tested by web-platform-tests >>> <https://chromium.googlesource.com/chromium/src/+/master/docs/testing/web_platform_tests.md> >>> ?Yes >>> >>> DevTrial instructions >>> https://github.com/w3c/media-source/issues/175#issuecomment-721395481 >>> >>> Flag nameMediaSourceInWorkers >>> >>> Requires code in //chrome?False >>> >>> Tracking bughttps://crbug.com/878133 >>> >>> Estimated milestones >>> OriginTrial desktop last 99 >>> OriginTrial desktop first 95 >>> OriginTrial android last 99 >>> OriginTrial android first 95 >>> >>> Link to entry on the Chrome Platform Status >>> https://chromestatus.com/feature/5177263249162240 >>> >>> Links to previous Intent discussionsIntent to prototype: >>> https://groups.google.com/u/1/a/chromium.org/g/blink-dev/c/CNRywDqgKjY/m/F0nnA4tTAwAJ >>> Intent to Experiment: >>> https://groups.google.com/a/chromium.org/g/blink-dev/c/XZMyanniH9E >>> >>> >>> This intent message was generated by Chrome Platform Status >>> <https://chromestatus.com/>. >>> >> -- You received this message because you are subscribed to the Google Groups "blink-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to blink-dev+unsubscr...@chromium.org. To view this discussion on the web visit https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAADho6MuWKkvBqhgE6Q7109-J6Yehcemhq4w7FbpUT0act%2BzJg%40mail.gmail.com.
