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Re: [css3-speech] cue volume

From: Alan Gresley <alan@css-class.com>
Date: Tue, 02 Aug 2011 17:44:53 +1000
Message-ID: <4E37AAF5.1010802@css-class.com>
To: fantasai <fantasai.lists@inkedblade.net>
CC: www-style@w3.org
On 2/08/2011 7:25 AM, fantasai wrote:
> On 08/01/2011 02:18 PM, Daniel Weck wrote:
>> Hi,
>> I have attempted to formulate a canonical expression of the concept of
>> intrinsic volume level for sound clips (pre-recorded / pre-generated)
>> so that authors can produce content with a good degree of confidence
>> that TTS voices render with predictable volume levels (e.g. comparable
>> loudness when no dB attenuation is specified). Reminder: the decibel
>> adjustments are relative to keyword values, which are user "preferred"
>> loudness settings (i.e. not known at authoring time). Let me know if
>> this is satisfactory, at least for a transition to Last Call Working
>> Draft :)
>> http://dev.w3.org/csswg/css3-speech/#cue-props
> I have no idea. It seems to make sense, but I don't know anything
> about sound recording / replaying volumes. :)
> ~fantasai

When recording, you must adjust the input level so sound with a largest 
amplitude does not get distorted. To set the best input level, you must 
sample the range of amplitude of different sounds (ei a double base or 
trumpet compared to a triangle). This is what happens at a concert where 
they do a sound check.

Playing back something is OK but an author can not know for sure how the 
sound will be replayed. One user could have there computer sound powered 
by a 500 watt external amplifier (stereo / surround system) where other 
users may be using a PC amplifier of 20 watts or headphones.

Another variable that is more dangerous is the setting of the volume. A 
user may go from listening to a YT video to listening to some music on a 
CD or DVD and adjust the volume at a desirable level. The spec would 
want to have UAs not deafen someone (or cause hearing damage) due to 
this unknown variable.

What is needed is something that plays sound at ever increasing levels 
until a level is reach that is desirable. This would have to be done 
over different octaves.

[1] http://en.wikipedia.org/wiki/Aliasing#Sample_frequency

Alan Gresley
Received on Tuesday, 2 August 2011 07:45:21 UTC

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