W3C home > Mailing lists > Public > public-html@w3.org > December 2009

Re: AW: Public feedback on HTML5 video

From: Philip Jägenstedt <philipj@opera.com>
Date: Mon, 28 Dec 2009 23:44:20 +0100
To: "Scheppe, Kai-Dietrich" <k.scheppe@telekom.de>, "Aryeh Gregor" <Simetrical+w3c@gmail.com>
Cc: HTMLwg <public-html@w3.org>
Message-ID: <op.u5n6r6l6sr6mfa@worf>
On Mon, 28 Dec 2009 22:11:49 +0100, Scheppe, Kai-Dietrich  
<k.scheppe@telekom.de> wrote:

>
>
>> - whether a poster frame is to be loaded or not (the poster attribute
>> does this)
>>   However, there is also mention of doing so only when no video is
>> available...that is not enough.  A poster frame should simply be a
>> choice of the author.
>
> I honestly don't understand what you are saying here. What is not enough?
> Does something need to be changed in the spec?
>
> Also Philip asked:
>
>> - whether a poster frame is to be loaded or not (the poster attribute
>> does this)
>>   However, there is also mention of doing so only when no video is
>> available...that is not enough.  A poster frame should simply be a
>> choice of the author.
>
> I honestly don't understand what you are saying here. What is not enough?
> Does something need to be changed in the spec?
>
>
> Kai:  With this I mean the spec currently mentions "The poster attribute  
> gives the address of an image file that the user agent can show while no  
> video data is available."
>
> What if the author wants to specfiy a poster image even though the video  
> data is available?
> That is what is not enough.

"When a video element is paused and the current playback position is the  
first frame of video, the element represents either the frame of video  
corresponding to the current playback position or the poster frame, at the  
discretion of the user agent.

Notwithstanding the above, the poster frame should be preferred over  
nothing, but the poster frame should not be shown again after a frame of  
video has been shown."

The only wiggle-room this leaves for implementation is whether to show the  
poster frame or the first video frame when the first video frame has been  
decoded. I think it should be the poster image, if other browser vendors  
agree perhaps the spec should simply say that.

>> - perhaps even where on the timeline the poster frame is to be found, if
>> it is not an explicit file
>
> The poster image can only be an image file, where from the video it is
> taken (if at all) hardly needs to be represented in HTML.
>
> Kai: Why ask the author to create a separate image if a frame of the  
> existing video is sufficient?

If the author doesn't want to use a poster image they simply shouldn't use  
that attribute. To show a certain frame of video, set .currentTime in a  
script. The poster attribute is just a convenience for a very common use  
case.

>> - the explicit dimensions of the video and let the video be covered
>> partially if it is larger than that.
>
> Let the video be covered by what? The poster image and video are never
> displayed at the same time.
>
> Kai: If the dimensions of the video are larger than the space alloted to  
> it, what is to happen?
> In CSS one option is to hide the content "behind" the surrounding  
> content.

"Video content should be rendered inside the element's playback area such  
that the video content is shown centered in the playback area at the  
largest possible size that fits completely within it, with the video  
content's aspect ratio being preserved. Thus, if the aspect ratio of the  
playback area does not match the aspect ratio of the video, the video will  
be shown letterboxed or pillarboxed. Areas of the element's playback area  
that do not contain the video represent nothing."

However, the CSS3 image-fit attribute should be able to override this, I'm  
not sure if the spec needs to change to allow this.

-- 
Philip Jägenstedt
Core Developer
Opera Software
Received on Monday, 28 December 2009 22:42:19 UTC

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