[whatwg] Audio canvas?

Mathieu HENRI p01 at opera.com
Wed Jul 16 06:41:14 PDT 2008

Dr. Markus Walther wrote:
>  >> My understanding of HTMLMediaElement is that the currentTime, volume
>  >> and playbackRate properties can be modified live.
>  >>
>  >> So in a way Audio is already like Canvas : the developer modify things
>  >> on the go. There is no automated animations/transitions like in SVG
>  >> for instance.
>  >>
>  >> Doing a cross fade in Audio is done exactly the same way as in Canvas.
> That's not what I described, however. Canvas allows access to the most 
> primitive element with which an image is composed, the pixel. Audio does 
> not allow access to the sample, which is the equivalent of pixel in the 
> sound domain. That's a severe limitation. Using tricks with data URIs 
> and a known simple audio format such as PCM WAVE is no real substitute, 
> because JavaScript strings are immutable.
> It is unclear to me why content is still often seen as static by default 
> - if desktop apps are moved to the browser, images and sound will 
> increasingly be generated and modified on-the-fly, client-side.


Having an equivalent of the ImageData for Audio would open some really 
interesting possibilities.

>  > And if you're thinking special effects ( e.g.: delay, chorus, flanger,
>  > pass band, ... ) remember that with Canvas, advanced effects require
>  > trickery and to composite multiple Canvas elements.
> I have use cases in mind like an in-browser audio editor for music or 
> speech applications (think 'Cooledit/Audacity in a browser'), where 
> doing everything server-side would be prohibitive due to the amount of 
> network traffic.

Mind you I have the same use cases.

> --Markus

Mathieu 'p01' HENRI
JavaScript developer, Opera Software ASA

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