On Mon, Nov 15, 2021 at 7:52 AM 'Hongchan Choi' via blink-dev < blink-dev@chromium.org> wrote:
> Thanks for the review, Yoav. My responses are inline: > > On Sun, Nov 14, 2021 at 10:48 PM Yoav Weiss <yoavwe...@chromium.org> > wrote: > >> >> >> On Fri, Nov 12, 2021 at 5:33 PM 'Ajay Rahatekar' via blink-dev < >> blink-dev@chromium.org> wrote: >> >>> Contact emails >>> >>> hongc...@chromium.org, ajayrahate...@google.com >>> >>> Explainer >>> >>> N/A - the specification (W3C Recommendation) is already published. >>> >> >> Regardless, could you add a few sentences explaining what use cases the >> feature targets and how developers are expected to use it? >> > > This feature can be useful when you need to synchronize a video stream (or > any kind of visual generated by the system) and an audio stream produced by > Web Audio API. For example, WebCodecs can be used to decode a MediaStream > into raw video and audio data, and then an app can apply processing only on > audio data via Web Audio API. This will break the original synchronization, > but this can be fixed by taking the hardware audio latency into account. > > >> >> >>> >>> Specification >>> >>> https://www.w3.org/TR/webaudio/#dom-audiocontext-outputlatency >>> >>> Summary >>> >>> AudioContext.outputLatency property is the estimation in seconds of >>> audio output latency. >>> >>> Technically, this is the interval between the time the UA requests the >>> host system to play a buffer and the time at which the first sample in the >>> buffer is actually processed by the audio output device. For devices such >>> as speakers or headphones that produce an acoustic signal, this latter time >>> refers to the time when a sample’s sound is produced. >>> >>> >>> Blink component >>> >>> Blink>WebAudio >>> <https://bugs.chromium.org/p/chromium/issues/list?q=component:Blink%3EWebAudio> >>> >>> TAG review >>> >>> Completed: Web Audio API specification is W3C Recommendation. >>> >> >> Link to the TAG review? >> > > https://github.com/w3ctag/design-reviews/issues/212 > > This was a blanket review for the entire API surface. No issues were > raised against the `outputLatency` property. > > >> >> >>> >>> TAG review status >>> >>> Completed: Web Audio API specification is W3C Recommendation. >>> >>> Risks >>> >>> There is a risk of the feature being used for fingerprinting. However >>> outputLatency >>> is the buffer size of the platform-provided audio callback, so the value is >>> inherently platform-specific. That said, the majority of the platform audio >>> buffer size is widely known. (MacOS = 128 frames, Windows = 10ms, Android = >>> 96 frames, etc) >>> >>> This feature does not expose more than what you can query/infer from >>> the UA string. >>> >> >> Would that exposure map cleanly to UA-Platform >> <https://wicg.github.io/ua-client-hints/#sec-ch-ua-platform>, which is >> considered low-entropy and exposed by default? Or would it add more than >> that? >> >> /cc +Mike Taylor <miketa...@chromium.org> >> > > I'll do some more investigation and follow up. > > >> >>> Interoperability and Compatibility >>> >>> Gecko: Shipped/Shipping >>> >> >> Link? >> > > https://bugzilla.mozilla.org/show_bug.cgi?id=1324552 > > >> >> >>> >>> WebKit: No signal >>> >> >> Have we reached out? https://bit.ly/blink-signals >> > > We have not reached out, and did not see any comments in the spec > discussion. > Ok. Please file a signals request on webkit-dev. > > >> >> >>> >>> Web developers: Positive ( >>> https://github.com/WebAudio/web-audio-api/issues/12) >>> >>> Other signals: A WebCodecs demo application needs this feature. >>> >>> >>> Is this feature fully tested by web-platform-tests >>> <https://chromium.googlesource.com/chromium/src/+/master/docs/testing/web_platform_tests.md> >>> ? >>> >>> No - this property represents a platform-provided output latency value >>> of a selected audio device. It does not work properly without an actual >>> audio device. >>> >> >> I'm guessing it is tested using browser tests or unit tests without an >> audio device, right? >> Have y'all filed bugs against WPT to enable testing it similarly? >> > > Currently we only have an IDL test: > > https://wpt.fyi/results/webaudio/idlharness.https.window.html?label=experimental&label=master&aligned > > No. We have not filed a bug for the new type of testing. I am not aware if > we have that kind of testing infrastructure on WPT. Please correct me if I > am mistaken. > > >> >> >>> Flag name >>> >>> N/A >>> >>> Requires code in //chrome? >>> >>> False >>> >>> Tracking bug >>> >>> http://crbug.com/785409 >>> >>> Launch bug >>> >>> http://crbug.com/1258109 >>> >>> Estimated milestones >>> >>> 98 >>> >>> >>> Link to entry on the Chrome Platform Status >>> >>> https://chromestatus.com/feature/5682265146261504 >>> >>> This intent message was generated by Chrome Platform Status >>> <https://www.chromestatus.com/>. >>> >>> >>> -- >>> Ajay Rahatekar | Technical Program Manager | ajayrahate...@google.com | >>> 650-797-1279 <(650)%20650-797-1279> >>> >>> -- >>> 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/CAHB%2BDAgeEo86rN4TrL4n8DutRczgXAogTwYLTo%2BPZco84aMq%3Dg%40mail.gmail.com >>> <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAHB%2BDAgeEo86rN4TrL4n8DutRczgXAogTwYLTo%2BPZco84aMq%3Dg%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- > 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/CAGJqXNv9r4hew4pknp-7iLHjP5hUY2mh1EkrHLFaeQaBzQf5VA%40mail.gmail.com > <https://groups.google.com/a/chromium.org/d/msgid/blink-dev/CAGJqXNv9r4hew4pknp-7iLHjP5hUY2mh1EkrHLFaeQaBzQf5VA%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- 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/CAOMQ%2Bw8qXWRZhaCpbQaOUsFWdaDLG8gdfjDxU6uzzVTKGgAfCA%40mail.gmail.com.
