voice-duration property is used in speech media for specifying how long it should take to render the selected element's content.
voice-duration property can be useful for cases where you need to synchronize the speech with other media.
The time value provided to this property specifies how long the element's content should take to render. Note that this doesn't include any rests, pauses, or cues (they will be added to the duration).
Note that the
voice-duration property takes precedence over the
voice-rate property (unless
auto is specified), and it can therefore be used to establish a speaking rate for the speech.
Also, when an element uses this property, its children cannot override its value (but only when the parent element has a non-
auto value). So, even if its children explicitly set the
voice-rate, these values are ignored (if the parent element uses a time value).
- Resolves to a used value corresponding to the duration of the speech synthesis when using the inherited
This value specifies a value in absolute time units (for example,
750ms, etc). Only non-negative values are allowed.
In addition, all CSS properties also accept the following CSS-wide keyword values as the sole component of their property value:
- Represents the value specified as the property's initial value.
- Represents the computed value of the property on the element's parent.
- This value acts as either
initial, depending on whether the property is inherited or not. In other words, it sets all properties to their parent value if they are inheritable or to their initial value if not inheritable.
- Initial Value
- Applies To
- All elements.
- CSS Speech Module (W3C Candidate Recommendation 20 March 2012)
For maximum browser compatibility many web developers add browser-specific properties by using extensions such as
-webkit- for Safari, Google Chrome, and Opera (newer versions),
-ms- for Internet Explorer,
-moz- for Firefox,
-o- for older versions of Opera etc. As with any CSS property, if a browser doesn't support a proprietary extension, it will simply ignore it.
This practice is not recommended by the W3C, however in many cases, the only way you can test a property is to include the CSS extension that is compatible with your browser.
The major browser manufacturers generally strive to adhere to the W3C specifications, and when they support a non-prefixed property, they typically remove the prefixed version. Also, W3C advises vendors to remove their prefixes for properties that reach Candidate Recommendation status.
Many developers use Autoprefixer, which is a postprocessor for CSS. Autoprefixer automatically adds vendor prefixes to your CSS so that you don't need to. It also removes old, unnecessary prefixes from your CSS.
You can also use Autoprefixer with preprocessors such as Less and Sass.