[whatwg] Codecs for <audio> and <video>

Ian Hickson ian at hixie.ch
Thu Jul 2 23:21:05 PDT 2009

On Thu, 2 Jul 2009, Charles Pritchard wrote:
> I'd like to see <canvas> support added to the <video> tag (it's as 
> natural as <img>).

<video> elements can be painted onto <canvas> elements already; did you 
have something more in mind?

> and enable the <audio> tag to accept raw data lpcm),
> just as the <canvas> tag accepts raw data (bitmap).

This is on the list of things to consider in a future version. At this 
point I don't really want to add new features yet because otherwise we'll 
never get the browser vendors caught up to implementing the same spec. :-)

> add raw pixel support to <video> (via CanvasRenderingContext2D).

Not really sure what this would look like. Can't you just do that with 
<canvas> already?

> And add an event handler when subtitles are enabled / disabled.

This is on the list for the next version. (Generally speaking, control 
over subtitles is one of the very next features that will be added.)

> > On Tue, 30 Jun 2009, Dr. Markus Walther wrote:
> >   
> > > > Having removed everything else in these sections, I figured there 
> > > > wasn't that much value in requiring PCM-in-Wave support. However, 
> > > > I will continue to work with browser vendors directly and try to 
> > > > get a common codec at least for audio, even if that is just 
> > > > PCM-in-Wave.
> I'd think that FLAC would make more sense than PCM-in-Wave, as a PNG 
> analog.

I encourage you to suggest this straight to the relevant vendors. As it 
stands, HTML5 is codec-neutral.

> I'd like to see a font analog in audio as well. Canvas supports the font 
> attribute, audio could certainly support sound fonts. Use a generated 
> pitch if your platform can't or doesn't store sound fonts.

This seems like an issue for the CSS or SVG working groups, who are 
working on font-related technologies.

> "User agents should provide controls to enable the manual selection of 
> fallback content."

There's no reason the UA couldn't provide an override mechanism to select 
an alternative source if the UA vendor so desires.

> "User agents should provide an activation behavior, when fallback 
> content is required, detailing why the primary content could not be 
> used."

There's no reason why UAs can't do that now. The spec doesn't prohibit 
such UI.

> Many non-technical users will want to know why there is a black screen 
> (or still image), even though they can hear the audio.

This kind of situation is of course why we really want to have a common 

Ian Hickson               U+1047E                )\._.,--....,'``.    fL
http://ln.hixie.ch/       U+263A                /,   _.. \   _\  ;`._ ,.
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