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Re: Codecs for <video> and <audio>

From: Doug Schepers <schepers@w3.org>
Date: Thu, 02 Jul 2009 21:11:45 -0400
Message-ID: <4A4D5AD1.7060603@w3.org>
To: Ian Hickson <ian@hixie.ch>
CC: Robert O'Callahan <robert@ocallahan.org>, David Singer <singer@apple.com>, Joe D Williams <joedwil@earthlink.net>, Maciej Stachowiak <mjs@apple.com>, public-html@w3.org
Hi, Ian-

Ian Hickson wrote (on 7/2/09 8:07 PM):
>
> Audio codecs really weren't part of my consideration; I removed audio
> codecs section just for consistency and because in the big picture it
> doesn't make any sense to have just that section if we don't have the
> others (since as far as I'm aware, all the codecs that we could put in
> this section -- namely just Wave PCM -- are being implemented by everyone
> anyway).

Not to be too facetious, but that's a bit like not including the <a> 
element because browsers will support it anyway.  One of the things I 
most admire about HTML5 is that, for all its flaws, it at least set out 
to document what browsers actually do.  Please don't make an exception 
in this critical instance.



> On Fri, 3 Jul 2009, Robert O'Callahan wrote:
>>  >  I really don't see much value in mentioning Wave PCM when we don't
>>  >  require any other codecs, image formats, etc.
>>
>>  The spec should require other codecs and image formats.
>
> This would be pretty unusual for W3C specs. Why the change?

Hardly unprecedented.  SVG requires "at least PNG, JPEG and SVG format 
files" for <image> support. [1] SMIL 3.0 says the following formats 
*should* be supported [2]
[[
     * audio/basic [MIME-2]
     * Ogg Vorbis audio (application/ogg) [VORBIS]
     * image/png [PNG-MIME], [PNG-REC]
     * image/jpeg [MIME-2], [JFIF] (See below)
     * Ogg Theora video (application/ogg) [THEORA]
]]

And suggests that "audio/AAC" and "video/H264" also be supported.

So, I'd expect at least as much from HTML5.


>>  >  I do think it would be useful to document the formats, codecs, and
>>  >  standards supported by all browsers, including things like PNG or Wave
>>  >  PCM, and including being specific about what versions or profiles of
>>  >  various specs are supported (e.g. the specific sampling frequencies of
>>  >  PCM). I don't think HTML5 is a particularly suitable place for such
>>  >  documentation, though.
>>
>>  HTML5 is a natural place for this, since authors using<img>  or<video>
>>  will be looking there already.
>
> Surely PNG support applies to SVG and CSS just as much, and XMLHttpRequest
> would need HTTP support as much (or as little!) as HTML, and so on. I
> don't see why this is HTML5-specific.

As noted above, SVG does mandate PNG.


>>  Even if a better place can be found, why not follow your previous policy
>>  of adding a section to HTML5 and moving it out if/when a better venue is
>>  found?
>
> Because this isn't required for interop, and so it's not critical.

Tell that to the authors who want to use a single format.  I don't think 
they'd agree.


[1] http://www.w3.org/TR/SVG11/struct.html#ImageElement
[2] http://www.w3.org/TR/SMIL/smil-profile.html#SMILProfileNS-MIMETypes

Regards-
-Doug Schepers
W3C Team Contact, SVG and WebApps WGs
Received on Friday, 3 July 2009 01:11:55 UTC

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