[webkit-dev] Position on emerging standard: video.requestAnimationFrame()

[Thomas Guilbert]

The living spec document can be found here:
https://wicg.github.io/video-raf/

On Wed, Feb 5, 2020 at 5:23 PM Thomas Guilbert <tguilbert at google.com> wrote:

> You're right, it doesn't in Chromium either (and I ran into that issue
> testing it :)). I will be updating the spec over the next few days.
>
> On Wed, Feb 5, 2020 at 5:09 PM Simon Fraser <simon.fraser at apple.com>
> wrote:
>
>> > On Feb 5, 2020, at 4:52 PM, Thomas Guilbert <tguilbert at google.com>
>> wrote:
>> >
>> > I am moving the execution of the video.rAF callbacks to be part of the
>> rendering steps. This should guarantee that "changes made inside the
>> callback appear at the same time as other changes in the same event loop
>> cycle".
>> > I don't know if there is a place within the rendering steps where it
>> makes most sense for them to run. I'm planning on having them run before
>> the window.rAF callbacks, but I don't know after which of the other steps
>> for now.
>> >
>> > That being said, if you paint a 24fps <video> into a <canvas> on every
>> video.rAF call, the canvas might still be 1/60th of a second behind the
>> video. This happens when we miss the rendering steps after jumping back on
>> the main thread, and have to wait for the next rendering steps (waiting
>> doesn't really change anything though, if the callbacks were fired earlier,
>> their changes would still appear later).
>> >
>> > Simon, does having video.rAF callbacks run as part of the rendering
>> steps address some of your concerns?
>>
>> It does, although I still don't like the name.
>>
>> The spec also needs somehow trigger the "update the rendering" steps if a
>> new video frame is available and there is a pending video.rAF (video
>> playback alone does not trigger the rendering steps, at least in WebKit,
>> for performance reasons).
>>
>> Simon
>>
>>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.webkit.org/pipermail/webkit-dev/attachments/20200228/4c5506d4/attachment.htm>