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Re: [css3-speech] voice-balance and azimuth

From: Daniel Weck <daniel.weck@gmail.com>
Date: Wed, 13 Jul 2011 18:40:08 +0100
Message-Id: <F20F7737-6C7C-4469-9D95-96C1061BA365@gmail.com>
To: www style <www-style@w3.org>, fantasai <fantasai.lists@inkedblade.net>

On 13 Jul 2011, at 18:12, fantasai wrote:

> On 07/13/2011 09:08 AM, Daniel Weck wrote:
>> Thank you for your feedback.
>> I have (majorly) re-formulated the prose to better express the relationship between the physical setup (user sound system) and the authored intent. I also added a section explaining the mapping to azimuth angles.
>> Please kindly review (as soon as you can):
>> 
>> http://dev.w3.org/csswg/css3-speech/#mixing-props-voice-balance
> 
> Much better! Here are my comments
> 
>  - Move the notes to the end of the section so they don't break
>    the flow of normative definition for the sound stage.

Done.

>  - The mapping to <angle> is incompatible with the definition
>    for stereo output, specifically:
> 
>      # When user-agents produce audio through a stereo sound
>      # system (e.g. two speakers, a pair of headphones), the
>      # left-right distribution of audio signals can precisely
>      # match the authored values for the ‘voice-balance’ property.
> 
>    vs.
> 
>      # The value ‘-100’ maps to -40 degrees (‘left’). Negative
>      # angles are in the counter-clockwise direction (the audio
>      # stage is seen from the top).
>      # The value ‘100’ maps to 40 degrees (‘right’). Positive
>      # angles are in the clockwise direction (the audio stage
>      # is seen from the top).
> 
>    For a pair of headphones, if you use the first definition,
>    'left' puts all the sound into the left earpiece. But if you
>    use the second definition, it will put some of the sound into
>    the right earpiece as well, because 40deg is not the left side,
>    but partway between the left side and the front center.


Are you saying that "voice-balance:left" should be equivalent to "azimuth:left-side" (-90 degrees)? (I am referring to the CSS2.1 Aural notation here)

On my 5.1 sound system, I would expect -90 degrees to produce sound from rear and front left speakers, so it seems quite logical that -40 degrees only produces audio output to the front left speaker (essentially equivalent to left-only perceived audio in a basic stereo system).

Actually, in a stereo system, azimuth angles between -40 and -180 degrees would all produce output in the left speaker only. There is simply no other way to reproduce the full granularity of the three-dimensional positioning, so users would be loosing definition / precision with basic stereo speaker.

This seems like a natural expectation. In other words, I agree with the scale specified in CSS2.1 Aural Stylesheets, and the syntax mapping between "voice-balance:left" and "azimuth:left".

http://www.w3.org/TR/CSS21/aural.html#spatial-props

/Daniel
Received on Wednesday, 13 July 2011 17:40:38 GMT

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