Html: The <video> poster attribute should accept multiple sources

[benwiley4000]

It's a shame we can't currently specify multiple poster image sources for a video element to be used depending on pixel density and size of the video element.

I'd propose that there be a posterset attribute similar to img srcset, if expanding the poster attribute's inputs seems unwise.

[benwiley4000]

cc @tabatkins re: srcset

[tabatkins]

Yeah, I'm def down with the concept. Question is just if we think there's a necessity for full art-direction (multiple source elements) or if it's fine to just provide different-density variants of the same image. I suspect the latter.

[benwiley4000]

I think I agree, although I want to make sure your suggestion accounts for variants based on size, not just density. Basically whatever the img srcset attribute supports.

[tabatkins]

srcset only allows varying on density. You can specify the density indirectly (via sizes and w), but all the variants are still required to be the exact same image, just at different densities.

If you want to change the size/aspect-ratio of the image, that's what you need multiple sources for in picture; that's less compatible with video, as it's already using source for something else. ^_^

[benwiley4000]

@tabatkins oh got it.

I agree there's no compelling reason to support multiple aspect ratios/multiple source elements.

Regarding size, I guess what I was looking for was a way to select the correct image url based on the w in srcset and the computed size of the video, without adding the sizes attribute - although maybe sizes would be required for that.