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Re: [css3-speech] pitch alteration expressed in semitones and Hertz

From: fantasai <fantasai.lists@inkedblade.net>
Date: Wed, 19 Jan 2011 14:33:07 -0800
Message-ID: <4D3766A3.2040804@inkedblade.net>
To: Daniel Weck <daniel.weck@gmail.com>
CC: www-style@w3.org
On 01/19/2011 01:19 PM, Daniel Weck wrote:
> Just in case this isn't obvious to those who are not familiar with the previous CSS3-Speech draft [1]:
> The 'voice-pitch' and 'voice-pitch-range' properties were already featured, but only with support for fixed Hertz values,
> predefined named values, and percentage values (allowing relative changes in a multiplicative fashion). There was a pending
> issue regarding a discrepancy with SSML 1.0, which enables relative changes in an additive fashion (increments and decrements
> of non-percentage / fixed values) using both Hertz units and semitones.
> I addressed this issue by adding an extra "value type" for the aforementioned properties, so the current specification is
> backward-compatible with the previous draft (none of the previous "value types" are affected by the change). Existing
> implementations only need to update the parsing algorithm, and to add the conversion from semitone offsets to fixed Hertz
> frequencies (which is based on trivial arithmetics).

The value type you are adding would be parsed as a dimension, similar to lengths.
This means the plus sign is in fact optional.

It might be worth investigating whether there are any implementations of the
CSS3 voice-pitch and voice-pitch-range properties. If there aren't, you will
have more freedom to change the syntax. Having numbers and Hz both refer to
hertz, but mean different things, for example, is imho somewhat confusing.
An alternative might be to add a keyword
   voice-pitch: <semitones> | [ <hertz> && absolute? ]
or somesuch.

Wrt implementations, the only two CSS Speech implementations I know of are
Opera's <http://www.opera.com/docs/specs/presto23/css/properties/> and
Emacspeak <http://emacspeak.sourceforge.net/>

Opera I believe follows the CSS3 drafts, but only has partial support;
Emacspeak claims full support for the CSS2 variant.

Received on Wednesday, 19 January 2011 22:33:45 UTC

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