The list of features is based on the W3C TTML/DFXP 1.0 test suite coverage document, and filled to the best of our knowledge based on analysis of current (as of Nov 2011) BBC toolset used to convert EBU-STL to TTML and a sample of resulting iPlayer subtitles (e.g.).
Obvious caveat: lack of implementation of a given feature does not imply that the BBC considers it to be useless/harmful.
| Feature | Section | Usage @BBC |
|---|---|---|
| ttp:profile | 6.1.1 | no |
| ttp:features | 6.1.2 | no |
| ttp:feature | 6.1.3 | no |
| ttp:extensions | 6.1.4 | no |
| ttp:extension | 6.1.5 | no |
| @ttp:cellResolution | 6.2.1 | yes (but not in use?) |
| @ttp:clockMode | 6.2.2 | no |
| @ttp:frameRate | 6.2.4 | yes (but not in use?) |
| @ttp:frameRateMultiplier | 6.2.4 | no |
| @ttp:subFrameRate | 6.2.9 | no |
| @ttp:markerMode | 6.2.6 | no (but assuming default) |
| @ttp:markerMode="continuous" | 6.2.6 | no (but assuming default) |
| @ttp:markerMode="discontinuous" | 6.2.6 | no |
| @ttp:pixelAspectRatio | 6.2.7 | no |
| @ttp:profile | 6.2.8 | no |
| @ttp:tickRate | 6.2.10 | yes (but not in use?) |
| @ttp:timeBase | 6.2.11 | yes |
| @ttp:timeBase="media" | 6.2.11 | yes |
| @ttp:timeBase="smpte" | 6.2.11 | yes |
| @ttp:timeBase="clock" | 6.2.11 | no (not used) |
| tt:tt | 7.1.1 | yes |
| tt:head | 7.1.2 | yes |
| tt:body | 7.1.3 | yes |
| tt:div | 7.1.4 | yes |
| tt:p | 7.1.5 | yes |
| tt:span | 7.1.6 | yes (but not in use?) |
| tt:br | 7.1.7 | yes |
| @xml:id | 7.2.1 | yes |
| @xml:lang | 7.2.2 | yes |
| @xml:space | 7.2.3 | no |
| @xml:space="default" | 7.2.3 | no |
| @xml:space="preserve" | 7.2.3 | no |
| tt:styling | 8.1.1 | yes |
| tt:style | 8.1.2 | yes |
| @style | 8.2.1 | yes |
| @tts:backgroundColor | 8.2.2 | yes |
| @tts:backgroundColor="<hash (rgb) color>" | 8.2.2 | no |
| @tts:backgroundColor="<hash (rgba) color>" | 8.2.2 | no |
| @tts:backgroundColor="<RGB color>" | 8.2.2 | no |
| @tts:backgroundColor="<RGBA color>" | 8.2.2 | no |
| @tts:backgroundColor="<named color>" | 8.2.2 | yes |
| @tts:color | 8.2.3 | yes |
| @tts:color="<hash (rgb) color>" | 8.2.3 | no |
| @tts:color="<hash (rgba) color>" | 8.2.3 | no |
| @tts:color="<RGB color>" | 8.2.3 | no |
| @tts:color="<RGBA color>" | 8.2.3 | no |
| @tts:color="<named color>" | 8.2.3 | no |
| @tts:direction | 8.2.4 | no |
| @tts:direction="ltr" | 8.2.4 | no |
| @tts:direction="rtl" | 8.2.4 | no |
| @tts:display | 8.2.5 | no |
| @tts:display="auto" | 8.2.5 | no |
| @tts:display="none" | 8.2.5 | no |
| @tts:displayAlign | 8.2.6 | yes |
| @tts:displayAlign="before" | 8.2.6 | no |
| @tts:displayAlign="center" | 8.2.6 | yes |
| @tts:displayAlign="after" | 8.2.6 | yes |
| @tts:extent | 8.2.8 | yes |
| @tts:extent="auto" | 8.2.8 | yes |
| @tts:extent="<length> <length>" | 8.2.8 | yes |
| @tts:fontFamily | 8.2.9 | yes |
| @tts:fontFamily="<familyName>" | 8.2.9 | yes |
| @tts:fontFamily="<familyName>(, <familyName>)+" | 8.2.9 | yes |
| @tts:fontSize | 8.2.10 | yes |
| @tts:fontSize="<length>" | 8.2.10 | yes |
| @tts:fontSize="<% length>" | 8.2.10 | no |
| @tts:fontSize="<px length>" | 8.2.10 | no |
| @tts:fontSize="<em length>" | 8.2.10 | no |
| @tts:fontSize="<c length>" | 8.2.10 | yes |
| @tts:fontSize="<length> <length>" | 8.2.10 | yes |
| @tts:fontStyle | 8.2.11 | yes |
| @tts:fontStyle="normal" | 8.2.11 | yes |
| @tts:fontStyle="italic" | 8.2.11 | yes |
| @tts:fontStyle="oblique" | 8.2.11 | no |
| @tts:fontStyle="reverseOblique" | 8.2.11 | no |
| @tts:fontWeight | 8.2.12 | yes |
| @tts:fontWeight="normal" | 8.2.12 | yes |
| @tts:fontWeight="bold" | 8.2.12 | no |
| @tts:lineHeight | 8.2.13 | no |
| @tts:lineHeight="normal" | 8.2.13 | no |
| @tts:lineHeight="<length>" | 8.2.13 | no |
| @tts:lineHeight="<% length>" | 8.2.13 | no |
| @tts:lineHeight="<px length>" | 8.2.13 | no |
| @tts:lineHeight="<em length>" | 8.2.13 | no |
| @tts:lineHeight="<c length>" | 8.2.13 | no |
| @tts:opacity | 8.2.14 | no |
| @tts:opacity="<alpha>" | 8.2.14 | no |
| @tts:origin | 8.2.15 | yes |
| @tts:origin="auto" | 8.2.15 | yes |
| @tts:origin="<length> <length>" | 8.2.15 | yes |
| @tts:overflow | 8.2.16 | no |
| @tts:overflow="visible" | 8.2.16 | no |
| @tts:overflow="hidden" | 8.2.16 | no |
| @tts:padding | 8.2.17 | no |
| @tts:padding="<length>" | 8.2.17 | no |
| @tts:padding="<% length>" | 8.2.17 | no |
| @tts:padding="<px length>" | 8.2.17 | no |
| @tts:padding="<em length>" | 8.2.17 | no |
| @tts:padding="<c length>" | 8.2.17 | no |
| @tts:padding="<length> <length>" | 8.2.17 | no |
| @tts:padding="<length> <length> <length>" | 8.2.17 | no |
| @tts:padding="<length> <length> <length> <length>" | 8.2.17 | no |
| @tts:showBackground | 8.2.18 | no |
| @tts:showBackground="always" | 8.2.18 | no |
| @tts:showBackground="whenActive" | 8.2.18 | no |
| @tts:textAlign | 8.2.19 | yes |
| @tts:textAlign="left" | 8.2.19 | yes |
| @tts:textAlign="center" | 8.2.19 | yes |
| @tts:textAlign="right" | 8.2.19 | yes |
| @tts:textAlign="start" | 8.2.19 | yes |
| @tts:textAlign="end" | 8.2.19 | yes |
| @tts:textDecoration | 8.2.20 | no |
| @tts:textDecoration="none" | 8.2.20 | no |
| @tts:textDecoration="underline" | 8.2.20 | no |
| @tts:textDecoration="noUnderline" | 8.2.20 | no |
| @tts:textDecoration="lineThrough" | 8.2.20 | no |
| @tts:textDecoration="noLineThrough" | 8.2.20 | no |
| @tts:textDecoration="overline" | 8.2.20 | no |
| @tts:textDecoration="noOverline" | 8.2.20 | no |
| @tts:textDecoration="(underline|lineThrough|overline){2}" | 8.2.20 | no |
| @tts:textDecoration="(underline|lineThrough|overline){3}" | 8.2.20 | no |
| @tts:textOutline | 8.2.21 | no |
| @tts:textOutline="none" | 8.2.21 | no |
| @tts:textOutline="<length>" | 8.2.21 | no |
| @tts:textOutline="<length> <length>" | 8.2.21 | no |
| @tts:textOutline="<color> <length>" | 8.2.21 | no |
| @tts:textOutline="<color> <length> <length>" | 8.2.21 | no |
| @tts:unicodeBidi | 8.2.22 | no |
| @tts:unicodeBidi="normal" | 8.2.22 | no |
| @tts:unicodeBidi="embed" | 8.2.22 | no |
| @tts:unicodeBidi="bidiOverride" | 8.2.22 | no |
| @tts:visibility | 8.2.23 | no |
| @tts:visibility="visible" | 8.2.23 | no |
| @tts:visibility="hidden" | 8.2.23 | no |
| @tts:wrapOption | 8.2.24 | no |
| @tts:wrapOption="wrap" | 8.2.24 | no |
| @tts:wrapOption="noWrap" | 8.2.24 | no |
| @tts:writingMode | 8.2.25 | no |
| @tts:writingMode="lrtb" | 8.2.25 | no |
| @tts:writingMode="rltb" | 8.2.25 | no |
| @tts:writingMode="tbrl" | 8.2.25 | no |
| @tts:writingMode="tblr" | 8.2.25 | no |
| @tts:writingMode="lr" | 8.2.25 | no |
| @tts:writingMode="rl" | 8.2.25 | no |
| @tts:writingMode="tb" | 8.2.25 | no |
| @tts:zIndex | 8.2.26 | yes (but never seen in practice) |
| @tts:zIndex="auto" | 8.2.26 | yes |
| @tts:zIndex="<integer>" | 8.2.26 | yes (but never seen in practice) |
| tt:layout | 9.1.1 | yes |
| tt:region | 9.1.2 | yes |
| @region | 9.2.1 | yes |
| @begin | 10.2.1 | yes |
| @begin="<clock-time>" | 10.2.1 | yes |
| @begin="<offset-time>h" | 10.2.1 | no |
| @begin="<offset-time>m" | 10.2.1 | no |
| @begin="<offset-time>s" | 10.2.1 | no |
| @begin="<offset-time>ms" | 10.2.1 | no |
| @begin="<offset-time>f" | 10.2.1 | no |
| @begin="<offset-time>t" | 10.2.1 | no |
| @end | 10.2.2 | yes |
| @end="<clock-time>" | 10.2.2 | yes |
| @end="<offset-time>" | 10.2.2 | no |
| @dur | 10.2.3 | no |
| @dur="<clock-time>" | 10.2.3 | no |
| @dur="<offset-time>" | 10.2.3 | no |
| @timeContainer | 10.2.4 | no |
| @timeContainer="par" | 10.2.4 | no |
| @timeContainer="seq" | 10.2.4 | no |
| tt:set | 11.1.1 | no |
| tt:metadata | 12.1.1 | yes |
| ttm:title | 12.1.2 | yes |
| ttm:desc | 12.1.3 | no |
| ttm:copyright | 12.1.4 | yes |
| ttm:agent | 12.1.5 | no |
| ttm:name | 12.1.6 | no |
| ttm:actor | 12.1.7 | no |
| @ttm:agent | 12.2.1 | no |
| @ttm:role | 12.2.2 | no |