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

Re: Public feedback on HTML5 video

From: Philip Jägenstedt <philipj@opera.com>
Date: Wed, 30 Dec 2009 10:42:44 +0100
To: "Silvia Pfeiffer" <silviapfeiffer1@gmail.com>
Cc: "Edward O'Connor" <hober0@gmail.com>, "Jeremy Keith" <jeremy@adactio.com>, HTMLwg <public-html@w3.org>
Message-ID: <op.u5qvxiiaatwj1d@sisko.linkoping.osa>
On Wed, 30 Dec 2009 03:57:33 +0100, Silvia Pfeiffer  
<silviapfeiffer1@gmail.com> wrote:

> On Wed, Dec 30, 2009 at 1:35 AM, Philip Jägenstedt <philipj@opera.com>  
> wrote:
>> On Tue, 29 Dec 2009 15:21:43 +0100, Silvia Pfeiffer
>> <silviapfeiffer1@gmail.com> wrote:
>>
>>> On Wed, Dec 30, 2009 at 1:13 AM, Philip Jägenstedt <philipj@opera.com>
>>> wrote:
>>>>
>>>> On Tue, 29 Dec 2009 14:26:44 +0100, Silvia Pfeiffer
>>>> <silviapfeiffer1@gmail.com> wrote:
>>>>
>>>>> On Tue, Dec 29, 2009 at 6:52 PM, Philip Jägenstedt  
>>>>> <philipj@opera.com>
>>>>> wrote:
>>>>>>
>>>>>> On Tue, 29 Dec 2009 00:44:50 +0100, Edward O'Connor  
>>>>>> <hober0@gmail.com>
>>>>>> wrote:
>>>>>>
>>>>>>>> Is the absence of the autobuffer attribute an explicit request  
>>>>>>>> not to
>>>>>>>> pre-buffer?
>>>>>>>
>>>>>>> I'd rather it not be.
>>>>>>>
>>>>>>> I think it's important for the author to be able to say "hi  
>>>>>>> browser,
>>>>>>> please do whatever is most appropriate given your platform /  
>>>>>>> network
>>>>>>> connection / memory / etc., insofar as buffering is concerned." In
>>>>>>> fact,
>>>>>>> I suspect this to be the most common authoring case. Most authors
>>>>>>> would
>>>>>>> prefer it if, say, cell phone browsers defaulted to  
>>>>>>> no-autobuffering,
>>>>>>> whereas they might prefer desktop browsers to behave differently.
>>>>>>> Given
>>>>>>> that, I'd prefer the default/lazy authoring behavior (not  
>>>>>>> specifying
>>>>>>> the
>>>>>>> attribute at all) to have this meaning.
>>>>>>>
>>>>>>> Essentially, we have three things we'd like authors to be able to
>>>>>>> convey
>>>>>>> to the browser:
>>>>>>>
>>>>>>>  1. Do whatever the browser thinks best.
>>>>>>>
>>>>>>>  2. Please autobuffer.
>>>>>>>
>>>>>>>  3. Please *don't* autobuffer.
>>>>>>>
>>>>>>> And there are a few things we'd like to be able to say about  
>>>>>>> whatever
>>>>>>> design we settle on:
>>>>>>>
>>>>>>>  A. (1) above should be the default condition, so its syntax  
>>>>>>> should be
>>>>>>>   what most authors will do anyway (not provide attributes at all).
>>>>>>>
>>>>>>>  B. Any new boolean attributes should behave like the other boolean
>>>>>>>   attributes already present in HTML (presence means t and absense
>>>>>>>   means nil).
>>>>>>>
>>>>>>>  C. If at all possible, we should be able to use different values  
>>>>>>> for
>>>>>>>   the same attribute for (2) and (3). (Minting separate attributes
>>>>>>>   for (2) and (3) means allowing authors to write nonsensical  
>>>>>>> markup,
>>>>>>>   and having to spec what HTML5 processors should do when they're
>>>>>>>   both present. What does <video buffer nobuffer> mean?)
>>>>>>>
>>>>>>> There's a lot of tension between (B) and (C), so much so that I  
>>>>>>> think
>>>>>>> autobuffer="" should probably become an enumerated attribute[1]
>>>>>>> instead
>>>>>>> of a boolean attribute. Something like the following:
>>>>>>>
>>>>>>>  1. Do whatever the browser thinks best. [no autobuffer attribute]
>>>>>>>
>>>>>>>  2. Please autobuffer. [autobuffer="on"]
>>>>>>>
>>>>>>>  3. Please *don't* autobuffer. [autobuffer="off"]
>>>>>>>
>>>>>>>
>>>>>>> Ted
>>>>>>>
>>>>>>> 1.
>>>>>>>
>>>>>>>
>>>>>>> http://www.whatwg.org/specs/web-apps/current-work/multipage/common-microsyntaxes.html#keywords-and-enumerated-attributes
>>>>>>>
>>>>>>
>>>>>> I do not support making this distinction, because as an implementor  
>>>>>> I
>>>>>> cannot
>>>>>> act any differently in case 1 and 3. Any browser that has gone to  
>>>>>> the
>>>>>> effort
>>>>>> of being conservative with network resources will want that behavior
>>>>>> even
>>>>>> if
>>>>>> autobuffer="off" is given. Unless there is some browser vendor who  
>>>>>> can
>>>>>> see
>>>>>> themselves acting differently in case 1 and 3, this just adds a bit  
>>>>>> of
>>>>>> complexity and the illusion of control on part of the author where
>>>>>> there
>>>>>> is
>>>>>> in fact none.
>>>>>
>>>>> I believe as a desktop browser on a web page with only one video in a
>>>>> prominent location ("above the fold"), I would decide to autobuffer.
>>>>> The same web page on a mobile phone browser, I would not decide to
>>>>> autobuffer.
>>>>>
>>>>> With more than one video on a page, I would probably autobuffer  
>>>>> nothing.
>>>>>
>>>>> This is a minor distinction though. Maybe you are right and there is
>>>>> never a need to autobuffer unless the autobuffer attribute is given.
>>>>> In this case, though, we should change the specification and make it
>>>>> clear that when autobuffer is given, it will autobuffer and when
>>>>> autobuffer is *not* given it will *not* autobuffer (unless autoplay  
>>>>> is
>>>>> given).
>>>>>
>>>>> There are in fact two problems with the current specification:
>>>>>
>>>>> 1. it doesn't allow specification by the page author to *not*
>>>>> autobuffer - all the page author (and user) can *hope* for is that by
>>>>> not specifying the attribute, the user agent will not buffer.
>>>>
>>>> It just seems to me that any sane browser would conserve bandwidth if  
>>>> it
>>>> knows how to, allowing the author to ask for that is a little bit like
>>>> <script slowdown="no">.
>>>
>>> I would say that John Gruber's discovery has contradicted this  
>>> statement.
>>
>> Isn't it just that most browsers (all except Firefox?) are ignoring the
>> autobuffer attribute? It seems that the solution is to implement
>> conservative network usage and to let the autobuffer attribute disable  
>> this
>> behavior. In my opinion, the difficult part is actually being  
>> conservative
>> to begin with and I don't know if there's any point in introducing  
>> shades of
>> conservative.
>
> So are you saying that most browsers have not implemented support of
> the autobuffer attribute yet and that is the real problem? If so, then
> it makes sense to have three states: when autobuffer is implemented
> and supported, "on" and "off" needs to be provided, which means "my
> browser has control over its buffering behaviour and I can give that
> control into the hands of the web developer". And if I do not
> implement autobuffer support, then what the video element does is
> random - depending on what is more convenient for my browser to do,
> i.e. the current state of when autobuffer is not in use.

Yes, the real problem is that it is much more difficult to be conservative  
with network resources than to just download the whole resource and it  
seems most browsers aren't done with their implementation. I expect that  
there are only two states however: trying being conservative and not.

> Or are you saying that really every browser should implement
> autobuffer support and then the lack of an autobuffer attribute
> signifies that it doesn't do autobuffering? In this case, we need to
> rewrite what the lack of @autobuffer means: no autobuffering.

I wouldn't really oppose making this explicit in the spec. However, I'm  
not sure how to make meaningful conformance requirements for "no  
autobuffering" as anything but downloading the whole resource should  
qualify. Not wasting network resources is just common sense, mandating it  
in the spec is really like asking browsers to execute scripts and decode  
images as fast as they can. However, if people are genuinely confused by  
the spec then I'm all for clarifying it.

> Shades of conservative is what we currently have: every browser can do
> what they like when no autobuffer is present. Firefox is more
> conservative than Safari. Instead, we need to clarify what is to be
> expected by a user.

What I mean is that no browser has shades of conservative, where they  
sometimes try a little bit harder to not waste bandwidth. Such an  
implementation is possible, but hypothetical at this point.

>>> Also, if we really are asking for no autobuffering when the attribute
>>> is not present, then this has to be stated in the HTML5 standard. So,
>>> either we introduce a autobuffer=yes/no option or we prescribe that
>>> when autobuffer is not present it means no autobuffering. Either
>>> requires a change to the spec.
>>
>> We could add a non-normative note to implementors that it's nice if they
>> don't waste bandwidth, even though I'm sure all implementors are already
>> very aware of this.
>
> Obviously not. Neither Safari nor Chrome implement conservative
> bandwidth behaviour - that's two out of three browsers that have
> decided (at least for now) to waste bandwidth. After this discussion,
> I'm sure they will all change it. But what about others who implement
> the text of the standard? They are not required or even requested to
> behave well. It does indeed need at minimum a recommendation, if not a
> requirement in the spec to make the browsers aware that they should
> behave conservative with bandwidth on video.

I don't believe that the reason browser are currently wasting bandwidth is  
because it never struck them, rather it's because it's actually quite  
difficult to implement conservative behavior and they haven't gotten to  
doing that yet. But enough speculation, I'm fine with any changes to the  
spec in this regard as long as they are either non-normative or have  
testable conformance requirements.

> I actually think that if it's not a required feature, ppl will avoid
> it since there are so many other features to implement. Our question
> here is: is this a feature that is absolutely necessary to make the
> video element usable or not. I believe that the discussions that have
> been stirred up through John Gruber's blog post show that it is a
> required feature - he clearly states it is "unusable" otherwise, and
> others have agreed.

I agree that it's not production-ready if browser aren't conservative with  
bandwidth. If a spec change can put pressure on browser vendors to fix  
this, sure. What concrete spec change though?

-- 
Philip Jägenstedt
Core Developer
Opera Software
Received on Wednesday, 30 December 2009 09:43:36 UTC

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