Re: [csswg-drafts] [css-grid][css-sizing] Aspect Ratio

#### tldr:
Aspect ratio is a thing in video, and we shouldn't create new problems there. Encouraging the viewport to be a different aspect ratio to the content has an accessibility impact.

#### Longer version:

Just want to call out that there's a potential impact here on users of video, who might be confused by this. In video it is common for different aspect ratios to be used and to modify the size of the video element automatically based on the content being played.

If a video element is given a specific aspect ratio, and that does not match the aspect ratio of the video content being played, what should happen?

For example, video content aspect ratio is 16:9, video viewport is 4:3. Should the video get black bars top and bottom, or should the central 4:3 section be shown only, omitting the 12.5% on either side?

This is a big deal for subtitles and captions authored with specific positions in mind, if those positions are specified with respect to the video viewport. It is typical to position subtitles to avoid obscuring important action happening in the video, for example a person's face when they are talking, the ball in a sports game, etc. It is important to have a clear positioning model in this case.

At the very least, whatever the implementation does with the video in this case needs to be available to player js code so that it can try to get the positioning correct.

Apologies if this is not the right place to raise this question. It just seems that introducing aspect ratio to CSS may exacerbate this issue, or confuse users, even if it is already possible to set the size of a video element explicitly to whatever aspect ratio is needed. For example now, it is possible to set `max-width: 100%;` alone on a `video` element, and the height is resolved automatically based on the aspect ratio of the content.

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Received on Friday, 26 October 2018 09:43:52 UTC