Re: Why is there no alt attribute associated with the poster attribute on a video element (or, what's the accessible name calculation on a video element

Hi Thrishma,

The problem is an architectural one: you cannot attach an attribute to
another attribute (and @poster is just that, an attribute).

We have two visual assets: one that moves (the mp4) and one that does not
(the jpg/png/"poster') - both will potentially require text alternatives.
 The video itself will also require 2 types of textual alternative: likely
a summarization of the video, as well as the captions which are actually
the text equivalent for the *audio* track.

The solution is to recognize that the poster is another related asset
associated with the movie, but not always *part* of the movie. We already
do that today with caption files and audio description files, where both
are called as child elements of the parent <video> element.

So, to really fix this and address the outstanding accessibility concern,
the solution would be to deprecate the @poster attribute and instead create
a <poster> element, which would be a different kind of child element (in
the same way that <track> is today). That way, we could then do something
like this:

<video>

    <track src="" kind="captions">

    <track src="" kind="descriptions"> <!-- audio descriptions -->

    <poster src="" alt="" aria-describedby=""> (and so on)

</video>

Respectfully,

JF

On Tue, May 19, 2020 at 10:32 AM thrishma reddy <thrishmareddy@gmail.com>
wrote:

> Hey Silvia,
>
> So to who do we ask/raise this issue for the alt attribute to be included
> in the <video> tag?
>
> This issue has been open for years and I wish there is finally someone we
> can reach out to who would actually solve this in 2020.
>
> Thanks,
> Thrishma
>
>
> On Mon, May 18, 2020 at 2:48 AM Silvia Pfeiffer <silviapfeiffer1@gmail.com>
> wrote:
>
>> Hi Thrisma,
>>
>> Hmm.... you're right - it only has a "title" attribute.
>> FWIW, I think it should have an explicit "alt" attribute.
>>
>> Just my 2c worth though.
>>
>> Cheers,
>> Silvia.
>>
>>
>> On Mon, May 18, 2020 at 8:02 AM thrishma reddy <thrishmareddy@gmail.com>
>> wrote:
>>
>>> Hi Silvia,
>>>
>>> Thanks for your reply. So when you say alt attribute for the video do
>>> you mean it looks like the below example?
>>>
>>> Example  -
>>>
>>> <video width="320" height="240" poster="/images/w3schools_green.jpg"
>>> controls *alt="Bear catching a fish in a river"*>
>>>    <source src="moviea.mp4" type="video/mp4">
>>>    <source src="movaie.ogg" type="video/ogg">
>>>    Your browser does not support the video tag.
>>> </video>
>>>
>>> There is no example of the video's alt attribute that I could find on
>>> the internet.
>>>
>>> I agree with you that there should be only one alternative field
>>> describing the video. The poster  image is the visual summary and the alt
>>> attribute is the textual summary of the video. There is no need to have an
>>> alt attribute for the poster image as it's only purpose is to be a visual
>>> summary of the video. This is true only when there exists an alt attribute
>>> for the <video> tag as shown in the above example. Otherwise, the poster
>>> property needs to have an alt attribute.
>>>
>>> Another question for you- When the source of an image is broken we
>>> display the alt text of the <img> tag. Does the alt property (if
>>> present) for the <video> tag do the same?
>>>
>>> Thanks,
>>> Thrishma
>>>
>>> On Sun, May 17, 2020 at 4:56 PM Silvia Pfeiffer <
>>> silviapfeiffer1@gmail.com> wrote:
>>>
>>>> Hey John,
>>>>
>>>> That's all a possibility, yes.
>>>>
>>>> So if your poster has different content from the video, your alt text
>>>> should include the poster description, too, because it's supported by
>>>> accessibility software. Introducing another attribute would require all
>>>> accessibility software to be updated with two text alternatives for one
>>>> element, which becomes very confusing very fast.
>>>>
>>>> Hope that helps.
>>>>
>>>> Best regards,
>>>> Silvia.
>>>>
>>>> On Sun, May 17, 2020, 11:17 PM John Foliot <john.foliot@deque.com>
>>>> wrote:
>>>>
>>>>> Silvia writes:
>>>>>
>>>>> > In essence: the poster is a visual summarisation of the video.
>>>>>
>>>>> Actually,  the poster  is  WAS ENVISIONED TO BE a visual
>>>>> summarisation of the video, by the former HTML5 editor, who also
>>>>> demonstrated on multiple occasions that he knew nothing of the
>>>>> accessibility space: the needs, the users, their user experience, etc. and
>>>>> he frequently demonstrated his lack of empathy in that regard.
>>>>>
>>>>> The reality is that the content author can point that @poster
>>>>> attribute to ANY graphic image URI, including interstitials and/or
>>>>> 'placeholder' slides (which may or may not contain "burned in" text
>>>>> intended for the end-user) a reality that some engineers simply refuse to
>>>>> accept as a possibility.
>>>>>
>>>>> Breaking this down:
>>>>>
>>>>> <video src="file.mp4"   <!-- this is a visual asset that requires a
>>>>> text alternative, AKA an AccessibleName. Given its complexity, it also
>>>>> needs an AccessibleDescription -->
>>>>>
>>>>>            poster="image.png">    <!-- this is a DIFFERENT visual
>>>>> asset that also *potentially *requires a text alternative, AKA an
>>>>> AccessibleName -->
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> > You only need one summary in text.
>>>>>
>>>>>
>>>>> Respectfully, you are wrong. I do not know where or how you arrive at
>>>>> this assertion, but it is simply and clearly wrong:
>>>>>
>>>>> *Success Criterion 1.1.1 Non-text Content (Level A)**:*
>>>>> *All non-text content* that is presented to the user has a text
>>>>> alternative that serves the equivalent purpose... (JF: ALL, not some)
>>>>>
>>>>> The text alternative is not a "summary", it is an alternative to the
>>>>> visual representation. Any time there is an image with text burned into it
>>>>> the textual alternative is not a summarization of that text: it must be
>>>>> faithfully and accurately replicated in text that can be processed by
>>>>> machine (i.e. a screen reader).
>>>>>
>>>>> Evidence for all of this was also brought forward "back in the day",
>>>>> along with multiple impassioned and detailed explanations about this topic
>>>>> by daily screen reader users. Please, listen to the end users - they know
>>>>> better than a sighted engineer will ever understand what they need and want.
>>>>>
>>>>> JF
>>>>>
>>>>> On Fri, May 15, 2020 at 5:18 PM Silvia Pfeiffer <
>>>>> silviapfeiffer1@gmail.com> wrote:
>>>>>
>>>>>> There were lengthy discussions about this back in the day - you
>>>>>> should be able to Google them.
>>>>>>
>>>>>> In essence: the poster is a visual summarisation of the video. The
>>>>>> video's alt tag is a text summarisation of the video. You only need one
>>>>>> summary in text.
>>>>>>
>>>>>> Hope this helps.
>>>>>>
>>>>>> Best regards,
>>>>>> Silvia.
>>>>>>
>>>>>>
>>>>>> On Fri, May 15, 2020, 12:59 AM thrishma reddy <
>>>>>> thrishmareddy@gmail.com> wrote:
>>>>>>
>>>>>>> Hello,
>>>>>>>
>>>>>>> I was wondering if there was ever any solution to the question asked
>>>>>>> here - https://github.com/w3c/html/issues/1431 (Why is there no alt
>>>>>>> attribute associated with the poster attribute on a video element (or,
>>>>>>> what's the accessible name calculation on a video element)?
>>>>>>>
>>>>>>>
>>>>>>> Thanks,
>>>>>>> Thrishma
>>>>>>>
>>>>>>>
>>>>>
>>>>> --
>>>>> *​John Foliot* | Principal Accessibility Strategist | W3C AC
>>>>> Representative
>>>>> Deque Systems - Accessibility for Good
>>>>> deque.com
>>>>> "I made this so long because I did not have time to make it shorter."
>>>>> - Pascal
>>>>>
>>>>>
>>>>>
>>>>>

-- 
*​John Foliot* | Principal Accessibility Strategist | W3C AC Representative
Deque Systems - Accessibility for Good
deque.com
"I made this so long because I did not have time to make it shorter." -
Pascal