-
Notifications
You must be signed in to change notification settings - Fork 790
Expand file tree
/
Copy pathOverview.src.html
More file actions
2141 lines (1803 loc) · 63.7 KB
/
Overview.src.html
File metadata and controls
2141 lines (1803 loc) · 63.7 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
<!DOCTYPE html PUBLIC '-//W3C//DTD HTML 4.01//EN'
'http://www.w3.org/TR/html4/strict.dtd'>
<html lang="en">
<head>
<title>CSS3 Speech Module</title>
<meta http-equiv="Content-Type" content="text/html; charset=us-ascii"/>
<link rel="stylesheet" type="text/css" href="default.css">
<style type="text/css">
.prod { font-family: inherit; font-size: inherit }
pre.prod { white-space: pre-wrap; margin: 1em 0 1em 2em }
code { font-size: inherit; }
#box-shadow-samples td { background: white; color: black; }
</style>
<style type="text/css">
/*<![CDATA[*/
caption { text-align: left; font-weight: bold }
.note { font-style: italic }
.issue { color: maroon; font-style: italic }
div.example pre { color: green; margin-left: 2em }
dl { margin-left: 2em }
caption dfn { font-size: 120% }
*:target {
color: #000000;
background-color: #F8F8F8;
border: 1px dashed #66CC66;
}
/*]]>*/
</style>
<link rel="stylesheet" type="text/css"
href="http://www.w3.org/StyleSheets/TR/W3C-WD.css">
</head>
<body>
<div class="head">
<!--logo-->
<h1 id="top">CSS3 Speech Module</h1>
<h2 class="no-num no-toc">[LONGSTATUS] [DATE]</h2>
<dl>
<dt>This version:
<dd><!--<a href="http://www.w3.org/TR/[YEAR]/WD-[SHORTNAME]-[CDATE]">[VERSION]</a>-->
<a href="http://dev.w3.org/csswg/css3-speech">http://dev.w3.org/csswg/css3-speech</a>
<dt>Latest version:
<dd><a
href="http://www.w3.org/TR/css3-speech">[LATEST]</a>
<dt>Previous versions:
<dd><a href="http://www.w3.org/TR/2004/WD-css3-speech-20041216/">http://www.w3.org/TR/2004/WD-css3-speech-20041216/</a>
<dt id="editors-list">Editors:
<dd><a href="mailto:dsr@w3.org">Dave Raggett</a> (<a href=
"http://www.w3.org/">W3C</a>/<a href="http://www.canon.com/">Canon</a>)</dd>
<dd><a href="mailto:daniel@glazman.org">Daniel Glazman</a> (<a href=
"http://www.disruptive-innovations.com/">Disruptive Innovations</a>)</dd>
<dd><a href="mailto:csant@opera.com">Claudio Santambrogio</a> (<a href=
"http://www.opera.com/">Opera Software</a>)</dd>
<dd><a href="mailto:dweck@daisy.org">Daniel Weck</a> (<a href=
"http://www.daisy.org">DAISY Consortium</a>)</dd>
</dl>
<!--copyright-->
<hr title="Separator for header">
</div>
<h2 id="abstract" class="no-num no-toc">Abstract</h2>
<p>CSS (Cascading Style Sheets) is a language for describing the
rendering of HTML and XML documents on screen, on paper, in speech,
etc. CSS defines aural properties that give control over rendering
XML and HTML to speech. This draft describes the text to speech properties
proposed for CSS level 3,
and is a re-work of the informative CSS2.1 Aural appendix [[CSS21]].
These are designed for match the model
described in the Speech Synthesis Markup Language (SSML) Version 1.0
[[!SPEECH-SYNTHESIS]].</p>
<p>The CSS3 Speech Module is a community effort and if you would
like to help with implementation and driving the specification
forward along the W3C Recommendation track, please contact the
editors.</p>
<h2 id="status" class="no-num no-toc">Status of this document</h2>
<!--status-->
<hr>
<p>This document is a draft of one of the "modules" for the
upcoming CSS3 specification.
<p>This document has been developed in
cooperation with the <a href="/Voice/Group/">Voice Browser working
group</a> (<a href="http://cgi.w3.org/MemberAccess/AccessRequest">W3C
Members only</a>).
<p>The following features are at-risk and may be dropped at the
end of the CR period if there has not been enough interest from
implementers: 'phonemes'
<p>The CSS WG maintains an <a href="http://www.w3.org/Style/CSS/Tracker/products/29">issues
list</a> for this module.
<h2 id="contents" class="no-num no-toc">Table of contents</h2>
<!--toc-->
<hr />
<h2 id="dependencies"><span class="secno">1. </span>Dependencies on other
modules</h2>
<p>This CSS3 module depends on the following other CSS3
modules:</p>
<ul>
<li>Values and Units [[!CSS3VAL]]</li>
</ul>
<p>It has non-normative (informative) references to the following
other CSS3 modules:</p>
<ul>
<li>Cascade and Inheritance [[CSS3CASCADE]]</li>
<li>Tables [[CSS3TBL]]</li>
<li>Syntax [[CSS3SYN]]</li>
<li>The box model [[CSS3BOX]]</li>
<li>Generated and Replaced Content [[CSS3GENCON]]</li>
<li>Selectors [[SELECT]]</li>
</ul>
<h2 id="introduction"><span class="secno">2. </span>Introduction</h2>
<p>The speech rendering of a document, already commonly used by
the blind and print-impaired communities, combines speech synthesis
and "auditory icons". Often such aural presentation occurs by
converting the document to plain text and feeding this to a
<dfn>screen reader</dfn> — software or hardware that simply
reads all the characters on the screen. This results in less
effective presentation than would be the case if the document
structure were retained. Style sheet properties for text to speech
may be used together with visual properties (mixed media) or as
an aural alternative to visual presentation.</p>
<p>Besides the obvious accessibility advantages, there are other
large markets for listening to information, including in-car use,
industrial and medical documentation systems (intranets), home
entertainment, and to help users learning to read or who have
difficulty reading.</p>
<p>When using voice properties, the canvas consists of a two
channel stereo space and a temporal space (you can specify
<a href="#cue-props">audio cues</a>
before and after synthetic speech). The CSS properties also
allow authors to vary the characteristics of synthetic speech
(voice type, frequency, inflection, etc.).</p>
<div class="example">
<p>Examples:</p>
<pre>
h1, h2, h3, h4, h5, h6 {
voice-family: paul;
voice-stress: moderate;
cue-before: url(ping.au)
}
p.heidi { voice-balance: left; voice-family: female }
p.peter { voice-balance: right; voice-family: male }
p.goat { voice-volume: soft }
</pre>
<p>This will direct the speech synthesizer to speak headers in a
voice (a kind of "audio font") called "paul". Before speaking the
headers, a sound sample will be played from the given URL.
Paragraphs with class "heidi" will appear to come from the left
(if the sound system is capable of stereo), and paragraphs of class
"peter" from the right. Paragraphs with class "goat" will be played
softly.</p>
</div>
<h2 id="aural-model"><span class="secno">3. </span>The aural "box" model</h2>
<p>The formatting model of CSS for aural media is based on a sequence
of sounds and silences that appear in a nested model which is
related to the visual box model; however the aural canvas is one-dimensional,
monolinear. For compatibility with the visual box model, we will call
it the <dfn id="aural-box-model">aural "box" model</dfn>.</p>
<p>The element is surrounded by, in this order, 'rest', 'cue'
and 'pause' properties - they can be thought of as aural equivalents
to 'padding', 'border' and 'margin' respectively.</p>
<p>It can be represented in the following way (including the equivalent
properties from the visual box model for clarification of relationships):</p>
<p><img id="aural-box" src="aural-box.png" alt="A graph depicting the aural 'box' model."/></p>
<p>where <dfn>element</dfn> is the selected element to which the properties
from the Speech Module apply.</p>
<h2 id="mixing-props"><span class="secno">4. </span>Mixing properties:
'voice-volume' and
'voice-balance'</h2>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="voice-volume">voice-volume</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><number> | <percentage> | silent | x-soft | soft |
medium | loud | x-loud | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>medium</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>yes</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>refer to inherited value</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>The 'voice-volume' refers to the amplitude of the waveform output by
the speech synthesiser. This may be mixed with other audio sources,
influencing the perceived loudness of synthetic speech relative
to these sources. Note that 'voice-volume' does not apply to <a href
="#cue-props">audio cues</a> for which there is a separate means
to set loudness (absolute, or relative to 'voice-volume').</p>
<p>Values have the following meanings:</p>
<dl>
<dt><strong><number></strong></dt>
<dd>An integer or floating point number in the range '0' to '100'.
'0' represents silence (the <em>minimum</em> level), and 100
corresponds to the <em>maximum</em> level. The volume scale is
linear amplitude.</dd>
<dt><strong><percentage></strong></dt>
<dd>Percentage values are calculated relative to the inherited
value, and are then clipped to the range '0' to '100'.</dd>
<dt><strong>silent</strong>,
<strong>x-soft</strong>,
<strong>soft</strong>,
<strong>medium</strong>,
<strong>loud</strong>, and
<strong>x-loud</strong></dt>
<dd>A sequence of monotonically non-decreasing volume levels. The value
of 'silent' is mapped to '0' and 'x-loud' is mapped to '100'.
The mapping of other values to numerical volume levels is implementation
dependent and may vary from one speech synthesizer to the next.</dd>
</dl>
<p>User agents should allow the level corresponding to '100' to be
set by the listener. No one setting is universally applicable;
suitable values depend on the equipment in use (speakers,
headphones), and the environment (in car, home theater, library)
and personal preferences.</p>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="voice-balance">voice-balance</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><number> | left | center | right | leftwards | rightwards | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>center</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>yes</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>N/A</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>The 'voice-balance' property refers to the balance between
left and right channels, and presumes a two channel (stereo) model
that is widely supported on consumer audio equipment.</p>
<p>Values have the following meanings:</p>
<dl>
<dt><strong><number></strong></dt>
<dd>An integer or floating point number between '-100' and '100'.
For '-100' only the left channel is audible. Simarly for '100' or
'+100' only the right channel is audible. For '0' both channels
have the same level, so that the speech appears to be coming from
the center.</dd>
<dt><strong>left</strong></dt>
<dd>Same as '-100'.</dd>
<dt><strong>center</strong></dt>
<dd>Same as '0'.</dd>
<dt><strong>right</strong></dt>
<dd>Same as '100' or '+100'.</dd>
<dt><strong>leftwards</strong></dt>
<dd>Moves the sound to the left, relative to the inherited
'voice-balance'. More precisely, subtract 20 from the inherited value and
clip the resulting value to the range '-100' and '100'.</dd>
<dt><strong>rightwards</strong></dt>
<dd>Moves the sound to the right, relative to the inherited
'voice-balance'. More precisely, add 20 to the inherited value and clip
the resulting value to the range '-100' and '100'.</dd>
</dl>
<p>Many speech synthesizers only support a single channel. The
'voice-balance' property can then be treated as part of a post
synthesis mixing step. This is where speech is mixed with other
audio sources. Note that unlike 'voice-volume', 'voice-balance'
<em>does</em> apply to <a href="#cue-props">audio cues</a>.</p>
<h2 id="speaking-props"><span class="secno">5. </span>Speaking properties:
'speak'</h2>
<!-- <p>An additional speech property, speak-header, is described in the
CSS module covering tables.</p> -->
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="speak">speak</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td>none | normal | spell-out | digits | literal-punctuation |
no-punctuation | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>normal</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>yes</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>N/A</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>This property specifies whether text will be rendered aurally
and if so, in what manner.</p>
<p>Values have the following meanings:</p>
<dl>
<dt><strong>none</strong></dt>
<dd>Suppresses aural rendering so that the element requires no time
to render. Note, however, that descendants may override this value
and will be spoken. (To be sure to suppress rendering of an element
and its descendants, use the 'display' property [[CSS3BOX]]).
<p class="issue">ISSUE: 'speak:none' is arguably unnecessary, as it can be fully realized using 'display:none' and because the function of 'speak' is primarily to specify *how* to speak text content, not to control *if* it should be spoken. There is also a concern about accessibility good practices, in particular with regards to whether this specification should allow authors to "hide" text in the aural dimension, when it is visible on the visual canvas. Note that "display:none" is different than "visibility:hidden". The former effectively 'deactivates' an element (so to speak) whereas the latter is more similar to "voice-volume:0%". In other words, "visibility:hidden" preserves the visual space that the element would normally occupy if it was visible (resulting in an empty or transparent area that still takes part in the page layout), and conversely "voice-volume:0%" results in an audio silence lasting as long as the duration of non-silent TTS playback.
</p>
</dd>
<dt><strong>normal</strong></dt>
<dd>Uses language-dependent pronunciation rules for rendering an
element and its children. Punctuation is not to be spoken, but
instead rendered naturally as various pauses.</dd>
<dt><strong>spell-out</strong></dt>
<dd>Spells the text one letter at a time (useful for acronyms and
abbreviations). In languages where accented characters are rare, it
is permitted to drop accents in favor of alternative unaccented
spellings. As as example, in English, the word "rôle" can
also be written as "role". A conforming implementation would thus
be able to spell-out "rôle" as "R O L E".</dd>
<dt><strong>digits</strong></dt>
<dd>Speak numbers one digit at a time, for instance, "twelve" would
be spoken as "one two", and "31" as "three one".</dd>
<dt><strong>literal-punctuation</strong></dt>
<dd>Similar to 'normal' value, but punctuation such as semicolons,
braces, and so on are to be spoken literally.</dd>
<dt><strong>no-punctuation</strong></dt>
<dd>Similar to 'normal' value but punctuation is not to be spoken
nor rendered as various pauses.</dd>
</dl>
<p>Note the difference between an element whose 'voice-volume'
property has a value of 'silent' and an element whose 'speak'
property has the value 'none'. The former takes up the same time as
if it had been spoken, including any pause before and after the
element, but no sound is generated. The latter requires no time and
is not rendered (though its descendants may be).</p>
<p>Speech synthesizers are knowledgeable about what is and what is
not a number. The 'speak' property gives authors the means to control
how the synthesizer renders the numbers it discovers in the source
text, and may be implemented as a preprocessing step before passing
the text to the speech synthesizer.</p>
<h2 id="pause-props"><span class="secno">6. </span>Pause properties:
'pause-before',
'pause-after' and
'pause',
<a href="#collapsing">collapsing pauses</a></h2>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="pause-before">pause-before</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><time> | none | x-weak | weak | medium | strong
| x-strong | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>implementation dependent</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>N/A</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p> </p>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="pause-after">pause-after</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><time> | none | x-weak | weak | medium | strong
| x-strong | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>implementation dependent</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>N/A</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>These properties specify a pause or prosodic boundary to be
observed before (or after) an element or, if any 'cue-before' (or
'cue-after') is specified, before (or after) these.</p>
<p>Values have the following meanings:</p>
<dl>
<dt><strong><time></strong></dt>
<dd>Expresses the pause in absolute time units (seconds and
milliseconds, e.g. "3s", "250ms"). Only positive values are allowed.</dd>
<dt><strong>none</strong>,
<strong>x-weak</strong>,
<strong>weak</strong>,
<strong>medium</strong>,
<strong>strong</strong>, and
<strong>x-strong</strong>
</dt>
<dd>These values may be used to indicate the prosodic strength of
the break in speech output. The synthesis processor may insert a
pause as part of its implementation of the prosodic break. The value
"none" indicates that no prosodic break boundary should be output,
and can be used to inhibit a prosodic break which the processor
would otherwise produce. The other values indicate monotonically
non-decreasing (conceptually increasing) break strength between
elements. "x-weak" and "x-strong" are mnemonics for "extra weak" and "extra
strong", respectively. The stronger boundaries are typically accompanied by pauses.
The breaks between paragraphs are typically much stronger than the breaks between words within a sentence.</dd>
</dl>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="pause">pause</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td>[ <'pause-before'> || <'pause-after'> ] |
inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>implementation dependent</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>N/A</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>The 'pause' property is a shorthand for setting 'pause-before'
and 'pause-after'. If two values are given, the first value is
'pause-before' and the second is 'pause-after'. If only one value
is given, it applies to both properties.</p>
<div class="example">
<p>Examples:</p>
<pre>
h1 { pause: 20ms } /* pause-before: 20ms; pause-after: 20ms */
h2 { pause: 30ms 40ms } /* pause-before: 30ms; pause-after: 40ms */
h3 { pause-after: 10ms } /* pause-before: <i>unspecified</i>; pause-after: 10ms */
</pre>
</div>
<h3 id="collapsing">Collapsing pauses</h3>
<p>The pause defines the minimum distance of the aural "box" to the
aural "boxes" before and after it. Adjacent pauses should be merged
by selecting the strongest named break or the longest absolute
time interval. Thus "strong" is selected when comparing "strong"
and "weak", while "1s" is selected when comparing "1s" and "250ms".
We say that such pauses <dfn id="collapse">collapse</dfn>.
A combination of a named break and time duration is treated
additively.</p>
<p>The following pauses collapse:</p>
<ol>
<li>The 'pause-after' of an aural "box" and the 'pause-after' of its last child,
provided the former has no 'rest-after' and no 'cue-after'.</li>
<
1337
div id="LC634" class="react-file-line html-div" data-testid="code-cell" data-line-number="634" style="position:relative"><li>The 'pause-before' of an aural "box" and the 'pause-before' of its first child,
provided the former has no 'rest-before' and no 'cue-before'.</li>
<li>The 'pause-after' of an aural "box" and the 'pause-before' of its next sibling.</li>
<li>The 'pause-before' and 'pause-after' of an aural "box", if the the "box" has a
'voice-duration' of "0ms", no 'rest-before' or 'rest-after', no
'cue-before' or 'cue-after' and no content.</li>
</ol>
<p>The 'pause-after' of an element is always adjoining to the 'pause-before' of its
next sibling.</p>
<p>The 'pause-before' an element is adjoining to its first child's 'pause-before',
if the element has no 'cue-before' nor 'rest-before'.</p>
<p>The 'pause-after' of an element is adjoining to its last child's 'pause-after',
if the element has no 'rest-after' or 'cue-after'.</p>
<p>An element's own pauses are adjoining if the 'voice-duration' property
is zero, and it has no rest, and it does not contain any content,
and all of its children's pauses (if any) are adjoining.</p>
<p class="note">Editor's note: 'pause' has been re-defined, and has
been moved from between the element's contents and any 'cue' to outside
the 'cue' - this is not backwards compatible with the informative CSS2.1
Aural appendix [[CSS21]].</p>
<h2 id="rest-props"><span class="secno">7. </span>Rest properties:
'rest-before',
'rest-after' and
'rest'</h2>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="rest-before">rest-before</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><time> | none | x-weak | weak | medium | strong
| x-strong | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>implementation dependent</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>N/A</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p> </p>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="rest-after">rest-after</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><time> | none | x-weak | weak | medium | strong
| x-strong | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>implementation dependent</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>N/A</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>These properties specify a rest or prosodic boundary to be observed
before (or after) speaking an element's content.</p>
<p>Values have the following
meanings:</p>
<dl>
<dt><strong><time></strong></dt>
<dd>Expresses the rest in absolute time units (seconds and milliseconds,
e.g. "3s", "250ms"). Only positive values are allowed.</dd>
<dt><strong>none</strong>,
<strong>x-weak</strong>,
<strong>weak</strong>,
<strong>medium</strong>,
<strong>strong</strong>, and
<strong>x-strong</strong>
</dt>
<dd>These values may be used to indicate the prosodic strength of
the break in speech output. The synthesis processor may insert a
rest as part of its implementation of the prosodic break. The value
"none" indicates that no prosodic break boundary should be output,
and can be used to inhibit a prosodic break which the processor
would otherwise produce. The other values indicate monotonically
non-decreasing (conceptually increasing) break strength between words.
The stronger boundaries are typically accompanied by rests. "x-weak"
and "x-strong" are mnemonics for "extra weak" and "extra strong",
respectively.</dd>
</dl>
<p>As opposed to <a href="#pause-props">pause properties</a>, the
rest is inserted between the element's content and any 'cue-before'
or 'cue-after' content. Adjacent rests are treated additively.</p>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="rest">rest</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td>[ <'rest-before'> || <'rest-after'> ] | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>implementation dependent</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>N/A</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>The 'rest' property is a shorthand for setting 'rest-before' and
'rest-after'. If two values are given, the first value is 'rest-before'
and the second is 'rest-after'. If only one value is given, it applies
to both properties.</p>
<h2 id="cue-props"><span class="secno">8. </span>Cue properties:
'cue-before',
'cue-after' and
'cue'</h2>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="cue-before">cue-before</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><uri> [<number> | <percentage> | silent
| x-soft | soft | medium | loud | x-loud] | none | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>none</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>apply to inherited value for 'voice-volume'</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p> </p>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="cue-after">cue-after</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td><uri> [<number> | <percentage> | silent
| x-soft | soft | medium | loud | x-loud] | none | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>none</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>apply to inherited value for 'voice-volume'</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>Auditory icons are another way to distinguish semantic elements.
Sounds may be played before and/or after the element to delimit it.
</p>
<p>Values have the following meanings:</p>
<dl>
<dt><strong><uri></strong></dt>
<dd>The URI must designate an auditory icon resource. If the URI
resolves to something other than an audio file, such as an image,
the resource should be ignored and the property treated as if it
had the value 'none'.</dd>
<dt><strong>none</strong></dt>
<dd>No auditory icon is specified.</dd>
<dt><strong><number></strong></dt>
<dd>An integer or floating point number in the range '0' to '100'.
'0' represents silence (the <em>minimum</em> level), and 100
corresponds to the <em>maximum</em> level. The volume scale is
linear amplitude.</dd>
<dt><strong><percentage></strong></dt>
<dd>Percentage values are calculated relative to the inherited
value of the 'voice-volume' property, and are then clipped to
the range '0' to '100'. By basing the percentage upon the
inherited value for 'voice-volume',
it is easy to adjust the relative loudness of cues compared to
synthetic speech for whatever volume setting has been provided
for that speech.</dd>
<dt><strong>silent</strong>,
<strong>x-soft</strong>,
<strong>soft</strong>,
<strong>medium</strong>,
<strong>loud</strong>, and
<strong>x-loud</strong></dt>
<dd>A sequence of monotonically non-decreasing volume levels.
The value of 'silent' is mapped to '0' and 'x-loud' is mapped
to '100'. The mapping of other values to numerical volume levels
is implementation dependent, but the intention is to match the
corresponding levels for 'voice-volume'.</dd>
</dl>
<div class="example">
<p>Examples:</p>
<pre>
a { cue-before: url(bell.aiff); cue-after: url(dong.wav) }
h1 { cue-before: url(pop.au) 80; cue-after: url(pop.au) 50% }
div.caution { cue-before: url(caution.wav) loud }
</pre>
</div>
<table class="propdef" summary="name: syntax">
<tbody>
<tr>
<td>Name:</td>
<td><dfn id="cue">cue</dfn></td>
</tr>
<tr>
<td width="20%"><em>Value:</em></td>
<td>[ <'cue-before'> || <'cue-after'> ] | inherit</td>
</tr>
<tr>
<td width="20%"><em>Initial:</em></td>
<td>not defined for shorthand properties</td>
</tr>
<tr>
<td width="20%"><em>Applies to:</em></td>
<td>all elements</td>
</tr>
<tr>
<td width="20%"><em>Inherited:</em></td>
<td>no</td>
</tr>
<tr>
<td width="20%"><em>Percentages:</em></td>
<td>apply to inherited value for 'voice-volume'</td>
</tr>
<tr>
<td width="20%"><em>Media:</em></td>
<td>speech</td>
</tr>
</tbody>
</table>
<p>The 'cue' property is a shorthand for setting 'cue-before'
and 'cue-after'. If two values are given the first value is
'cue-before' and the second is 'cue-after'. If only one value
is given, it applies to both properties.</p>
<div class="example">
<p>The following two rules are equivalent:</p>
<pre>
h1 {cue-before: url(pop.au); cue-after: url(pop.au) }
h1 {cue: url(pop.au) }
</pre></div>
<p>If a user agent cannot render an auditory icon (e.g., the
user's environment does not permit it), we recommend that it
produce an alternative audio cue (e.g., popping up a warning, emitting
a warning sound, etc.)</p>
<p>Authors may also use
<a href="#content">content generation techniques</a>
to insert additional auditory cues based on text instead of audio icons.</p>
<!-- Add something here about gc -->