New Playback Requirement: Playback Other than Real Time

cta-wave / device-playback-task-force

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New Playback Requirement: Playback Other than Real Time #49

Open haudiobe opened 5 years ago

haudiobe commented 5 years ago

8.16 Playback Other than Real Time 8.16.1 Background This test refers to the playback of content faster or slower than real-time, or even in reverse direction. Content conforms even in different speed to the profile/level constraints of decoder. There are three ways to do this: • Play at X times as long as it is in the decoder profile/level constraint (app forwards all content to the device and device plays with X times). • Use special content (e.g., I-frame only content, to address any of these issues – and use the above). • Download key frames from regular content and feed those into the MSE source buffer.

The first version of this specification does not define a test for this.

haudiobe commented 4 years ago

Overlaps with Low Latency #71 - merge

https://www.w3.org/TR/html51/semantics-embedded-content.html#playing-the-media-resource

De-prioritize this one, merge into #71

dsilhavy commented 3 years ago

Note: reverse playback/negative playback rates are not supported natively by the HTML5 video element: https://developer.mozilla.org/en-US/docs/Web/API/HTMLMediaElement/playbackRate

If playbackRate is negative, the media is not played backwards.

Related request for dash.js: https://github.com/Dash-Industry-Forum/dash.js/issues/3570

jpiesing commented 3 years ago

If playbackRate is negative, the media is not played backwards.

Interesting. That restriction is not in the HTML spec and indeed could be argued to conflict with the HTML spec which explicitly addresses negative playback.

dsilhavy commented 3 years ago

Interesting. I did a quick check for negative playback rates

Chrome throws: VM16730:1 Uncaught DOMException: Failed to set the 'playbackRate' property on 'HTMLMediaElement': The provided playback rate (-0.1) is not in the supported playback range.
Firefox throws: Uncaught DOMException: Operation is not supported
Safari: No error, but seems to adjust everything <0 to 0. So playback pauses.

andyburras commented 3 years ago

I did a quick check for negative playback rates

Interesting. One to check with HATF, but as the WMAS snapshot and WPT testing is based on the common functionality supported by the current mainstream browser code bases then I guess this falls outside WAVE scope?

haudiobe commented 2 years ago

Not part of new tests - may be removed

gitwjr commented 1 year ago

Deferred for future work.

haudiobe commented 2 months ago

this seems to be implemented now

jpiesing commented 2 months ago

this seems to be implemented now

Yes, this is essentially a superset of #71 and the proposed implementation of that is sufficiently generalised the playback rates are read in from a config file and the code and media is the same.

haudiobe commented 4 days ago

Implemented with #71