1. Add terminology items (2.2):
authorGlenn Adams <glenn@skynav.com>
Wed, 27 Jun 2012 23:16:08 -0600
changeset 25025d99500be0c
parent 249 4567470f27ea
child 251 81b0eec0faae
1. Add terminology items (2.2):
* Document Processing Context
* Related Media Object
* SMPTE Time Code
* Synthetic Document Syncbase
* Synthetic SMPTE Document Syncbase
2. Clarify semantics of marker mode using new Synthetic SMPTE Document Syncbase concept (6.2.6).
3. Change default (unspecified) value of marker mode to discontinuous. Add (historical) note explaining change (6.2.6).
4. Elaborate semantics of time intervals and expressions when using smpte time base (10.4).
5. Editorial fixes with respect to 'time mode' vs 'time base' (10.4).
6. Editorial fixes with respect to 'wallclock' vs 'wall-clock' (*).
ttml10/spec/ttaf1-dfxp.xml
     1.1 --- a/ttml10/spec/ttaf1-dfxp.xml	Thu Jun 14 07:46:46 2012 -0600
     1.2 +++ b/ttml10/spec/ttaf1-dfxp.xml	Wed Jun 27 23:16:08 2012 -0600
     1.3 @@ -509,13 +509,13 @@
     1.4  <p>Timed Text</p>
     1.5  </def>
     1.6  </gitem>
     1.7 -  <gitem>
     1.8 -    <label>TTML</label>
     1.9 -    <def>
    1.10 -      <p>Timed Text Markup Language</p>
    1.11 -    </def>
    1.12 -  </gitem>
    1.13 -  <gitem>
    1.14 +<gitem>
    1.15 +<label>TTML</label>
    1.16 +<def>
    1.17 +<p>Timed Text Markup Language</p>
    1.18 +</def>
    1.19 +</gitem>
    1.20 +<gitem>
    1.21  <label>TT AS</label>
    1.22  <def>
    1.23  <p>Timed Text Authoring System</p>
    1.24 @@ -591,11 +591,20 @@
    1.25  <label>Document Interchange Context</label>
    1.26  <def>
    1.27  <p>The implied context or environment external to a <emph>Content Processor</emph> in
    1.28 -which document interchange occurs, and in which out-of-band protocols or procedures
    1.29 +which document interchange occurs, and in which out-of-band protocols or specifications
    1.30  may define certain behavioral defaults, such as an implied <emph>Content Profile</emph>.</p>
    1.31  </def>
    1.32  </gitem>
    1.33  <gitem>
    1.34 +<label>Document Processing Context</label>
    1.35 +<def>
    1.36 +<p>The implied context or environment internal to a <emph>Content Processor</emph> in
    1.37 +which document processing occurs, and in which out-of-band protocols or specifications
    1.38 +may define certain behavioral defaults, such as the establishment or creation of a
    1.39 +<emph>Synthetic Syncbase</emph>.</p>
    1.40 +</def>
    1.41 +</gitem>
    1.42 +<gitem>
    1.43  <label>Element Information Item</label>
    1.44  <def>
    1.45  <p>Each element appearing in an XML document corresponds with an element information
    1.46 @@ -663,6 +672,15 @@
    1.47  </def>
    1.48  </gitem>
    1.49  <gitem>
    1.50 +<label>Related Media Object</label>
    1.51 +<def>
    1.52 +<p>A (possibly null) media object associated with or otherwise related
    1.53 +to a TTML document instance. For example, an aggregate audio/video media
    1.54 +object for which a TTML document instance provides caption or subtitle
    1.55 +information, and with which that TTML document instance is associated.</p>
    1.56 +</def>
    1.57 +</gitem>
    1.58 +<gitem>
    1.59  <label>Root Container Region</label>
    1.60  <def>
    1.61  <p>A logical region that establishes a coordinate system into which
    1.62 @@ -670,6 +688,30 @@
    1.63  </def>
    1.64  </gitem>
    1.65  <gitem>
    1.66 +<label>SMPTE Time Code</label>
    1.67 +<def>
    1.68 +<p>A time code whose format and semantics is established by <bibref ref="smpte12m"/>
    1.69 +which may be embedded into or otherwise associated with media content, such
    1.70 +as a broadcast audio/video stream.</p>
    1.71 +</def>
    1.72 +</gitem>
    1.73 +<gitem>
    1.74 +<label>Synthetic Document Syncbase</label>
    1.75 +<def>
    1.76 +<p>A document level syncbase synthesized or otherwise established by
    1.77 +the <emph>Document Processing Context</emph> in accordance with the
    1.78 +<emph>Related Media Object</emph> or other processing criteria.</p>
    1.79 +</def>
    1.80 +</gitem>
    1.81 +<gitem>
    1.82 +<label>Synthetic SMPTE Document Syncbase</label>
    1.83 +<def>
    1.84 +<p>A <emph>Synthetic Document Syncbase</emph> constructed from <emph>SMPTE Time
    1.85 +Code</emph> values embedded in or associated with the <emph>Related Media Object</emph> or
    1.86 +otherwise determined by the <emph>Document Processing Context</emph>.</p>
    1.87 +</def>
    1.88 +</gitem>
    1.89 +<gitem>
    1.90  <label>Timed Text</label>
    1.91  <def>
    1.92  <p>Textual information that is intrinsically or extrinsically
    1.93 @@ -2340,21 +2382,33 @@
    1.94  decreasing; however, if <code>discontinuous</code>, then any assumption
    1.95  must not be made regarding linearity or monotonicity of time coordinates.</p>
    1.96  <p>If not specified, the value of this parameter must be considered
    1.97 -to be <code>continuous</code>.</p>
    1.98 +to be <code>discontinuous</code>.</p>
    1.99 +<note role="historical">
   1.100 +<p>The default value for this parameter was originally specified
   1.101 +(in <xspecref href="http://www.w3.org/TR/2010/REC-ttaf1-dfxp-20101118/">TTML 1.0 First Edition</xspecref>)
   1.102 +as <code>continuous</code>; however, further evaluation of the state of the industry indicates this
   1.103 +choice was incorrect, and that the most common default is <code>discontinuous</code>.</p>
   1.104 +</note>
   1.105  <p>A <att>ttp:markerMode</att> attribute is considered to be significant only
   1.106  when specified on the <el>tt</el> element.</p>
   1.107  <p>If a value of <code>continuous</code> applies, then time
   1.108  expressions may be converted to real time
   1.109  coordinates by taking into account the computed frame rate
   1.110 -and drop mode as expressed by the <att>ttp:dropMode</att> parameter.</p>
   1.111 +and drop mode as expressed by the <att>ttp:dropMode</att> parameter.
   1.112 +In this case, the <emph>Content Processor</emph> must create and maintain a
   1.113 +<emph>Synthetic SMPTE Document Syncbase</emph> within which these time
   1.114 +expressions are interpreted as further described in
   1.115 +<specref ref="timing-time-intervals"/>.</p>
   1.116  <note role="explanation">
   1.117  <p>When operating with <code>smpte</code> time base and
   1.118  <code>continuous</code> marker mode, there is an implied time coordinate
   1.119 -space, defined by the monotonically increasing (or decreasing) 
   1.120 +space, the <emph>Synthetic SMPTE Document Syncbase</emph>,
   1.121 +defined by the monotonically increasing (or decreasing) 
   1.122  <bibref ref="smpte12m"/> time coordinates, while taking into account
   1.123  the computed frame rate and drop mode. All time expressions are interpreted
   1.124 -as labeled synchronization events (markers), where some external
   1.125 -synchronization context emits these events with implied constraints
   1.126 +in relationship to this time coordinate space based upon
   1.127 +<emph>SMPTE Time Code</emph> synchronization events (markers),
   1.128 +where the <emph>Document Processing Context</emph>  emits these events with implied constraints
   1.129  regarding time coordinate monoticity and resynchronization in
   1.130  the presence of dropped frames.</p>
   1.131  <p>Use of <code>continuous</code> marker mode with the <code>smpte</code>
   1.132 @@ -2374,8 +2428,8 @@
   1.133  <p>When operating with <code>smpte</code> time base and
   1.134  <code>discontinuous</code> marker mode, there is no effective time coordinate
   1.135  space; rather, all time expressions are interpreted as labeled
   1.136 -synchronization events (markers), where some external synchronization
   1.137 -context emits these events, which, when they correspond with time
   1.138 +synchronization events (markers), where the <emph>Document Processing Context</emph>
   1.139 +emits these events, which, when they correspond with time
   1.140  expressions that denote the same label, cause a temporal interval to
   1.141  begin or end accordingly.</p>
   1.142  <p>An additional side-effect of operating in <code>discontinuous</code>
   1.143 @@ -7714,23 +7768,12 @@
   1.144  constraints:</p>
   1.145  <ulist>
   1.146  <item>
   1.147 -<p>The implicit duration of
   1.148 -
   1.149 -an anonymous span
   1.150 -
   1.151 -is defined as follows: if
   1.152 -the
   1.153 -
   1.154 -anonymous span's
   1.155 -
   1.156 -parent time container is a parallel time container, then
   1.157 +<p>The implicit duration of an anonymous span is defined as follows: if
   1.158 +the anonymous span's parent time container is a parallel time container, then
   1.159  the implicit duration is equivalent to the <code>indefinite</code>
   1.160 -duration value as defined by <bibref ref="smil21"/>; if the
   1.161 -
   1.162 -anonymous span's
   1.163 -
   1.164 -parent time container is a sequential time container, then the
   1.165 -implicit duration is equivalent to zero.</p>
   1.166 +duration value as defined by <bibref ref="smil21"/>; if the anonymous span's
   1.167 +parent time container is a sequential time container, then the implicit duration
   1.168 +is equivalent to zero.</p>
   1.169  </item>
   1.170  <item>
   1.171  <p>The implicit duration of a <el>body</el>, <el>div</el>, <el>p</el>,
   1.172 @@ -7745,24 +7788,51 @@
   1.173  duration value as defined by <bibref ref="smil21"/>.</p>
   1.174  </item>
   1.175  <item>
   1.176 -<p>If the governing time mode is <code>media</code> or
   1.177 -<code>smpte</code> with mode <code>continuous</code>, then time
   1.178 -expressions must be interpreted as
   1.179 -equivalent to offset based timing
   1.180 +<p>If the governing time base is <code>media</code>, then time
   1.181 +expressions must be interpreted as equivalent to offset based timing
   1.182  in <bibref ref="smil21"/>, namely, as offsets from an implicit
   1.183  syncbase.</p>
   1.184  </item>
   1.185  <item>
   1.186 -<p>If the governing time mode is <code>smpte</code> with mode
   1.187 -<code>discontinuous</code>, then time expressions must be interpreted
   1.188 -as equivalent to marker values produced by an external marker event
   1.189 -source, in which case all time expressions are equivalent to event
   1.190 +<p>If the governing time base is <code>smpte</code> with <code>continuous</code> marker mode,
   1.191 +then time expressions must be interpreted as follows:</p>
   1.192 +<ulist>
   1.193 +<item>
   1.194 +<p>If the time expression is an <code>offset-time</code> expression, then it must be
   1.195 +interpreted as equivalent to offset based timing in <bibref ref="smil21"/>, where the
   1.196 +offset is in relationship to the applicable implicit syncbase.</p>
   1.197 +</item>
   1.198 +<item>
   1.199 +<p>If the time expression is a <code>clock-time</code> expression, then it must be
   1.200 +interpreted as equivalent to offset based timing in <bibref ref="smil21"/>, where the
   1.201 +offset is in relationship to the <emph>Synthetic SMPTE Document Syncbase</emph>. For example,
   1.202 +if the begin time of this synthetic syncbase is associated with the
   1.203 +time code <code>10:00:00:00.0</code>, then the appearance of time expression <code>11:00:00:00.0</code>
   1.204 +is interpreted as equivalent to expressing an <code>offset-time</code> expression
   1.205 +of <code>1h</code> where the applicable implicit syncbase is the <emph>Synthetic SMPTE Document Syncbase</emph>.</p>
   1.206 +</item>
   1.207 +</ulist>
   1.208 +</item>
   1.209 +<item>
   1.210 +<p>If the governing time base is <code>smpte</code> with <code>discontinuous</code> marker mode,
   1.211 +then time expressions must be interpreted as follows:</p>
   1.212 +<ulist>
   1.213 +<item>
   1.214 +<p>If the time expression is an <code>offset-time</code> expression, then it must be
   1.215 +interpreted as an error.</p>
   1.216 +</item>
   1.217 +<item>
   1.218 +<p>If the time expression is a <code>clock-time</code> expression, then it must be
   1.219 +interpreted as equivalent to marker values produced by an external marker event
   1.220 +source, in which case the time expression is equivalent to event
   1.221  based timing in <bibref ref="smil21"/>.</p>
   1.222  </item>
   1.223 -<item>
   1.224 -<p>If the governing time mode is <code>clock</code>, then time
   1.225 -expressions must be interpreted as equivalent to wallclock time
   1.226 -expressions in <bibref ref="smil21"/>, where the applicable wallclock
   1.227 +</ulist>
   1.228 +</item>
   1.229 +<item>
   1.230 +<p>If the governing time base is <code>clock</code>, then time
   1.231 +expressions must be interpreted as equivalent to wall-clock time
   1.232 +expressions in <bibref ref="smil21"/>, where the applicable wall-clock
   1.233  used is determined by the clock mode parameter.</p>
   1.234  </item>
   1.235  </ulist>
   1.236 @@ -11777,7 +11847,7 @@
   1.237  <td>R404</td>
   1.238  <td>Synchronization Parameter Value Spaces</td>
   1.239  <td>P</td>
   1.240 -<td>Supports offset values, media marker values (SMPTE 12M), wallclock values</td>
   1.241 +<td>Supports offset values, media marker values (SMPTE 12M), wall-clock values</td>
   1.242  </tr>
   1.243  <tr>
   1.244  <td>R405</td>
   1.245 @@ -12529,7 +12599,7 @@
   1.246  or <code>clock</code>, respectively:
   1.247  (1) an offset from an implicit syncbase that is linked to a media time
   1.248  line, (2) an event time
   1.249 -that represents the occurrence of an implicit media marker, or (3) a wallclock
   1.250 +that represents the occurrence of an implicit media marker, or (3) a wall-clock
   1.251  time.</p>
   1.252  </item>
   1.253  <item>