ISO/IEC 14496-30:2018/Amd 1:2022
(Amendment)Information technology — Coding of audio-visual objects — Part 30: Timed text and other visual overlays in ISO base media file format — Amendment 1: Timing improvements
Information technology — Coding of audio-visual objects — Part 30: Timed text and other visual overlays in ISO base media file format — Amendment 1: Timing improvements
Technologies de l'information — Codage des objets audiovisuels — Partie 30: Texte temporisé et autres recouvrements visuels dans le format ISO de base pour les fichiers médias — Amendement 1: Améliorations des temporisations
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INTERNATIONAL ISO/IEC
STANDARD 14496-30
Second edition
2018-11
AMENDMENT 1
2022-06
Information technology — Coding of
audio-visual objects —
Part 30:
Timed text and other visual overlays
in ISO base media file format
AMENDMENT 1: Timing improvements
Technologies de l'information — Codage des objets audiovisuels —
Partie 30: Texte temporisé et autres recouvrements visuels dans le
format ISO de base pour les fichiers médias
AMENDEMENT 1: Améliorations des temporisations
Reference number
ISO/IEC 14496-30:2018/Amd. 1:2022(E)
© ISO/IEC 2022
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ISO/IEC 14496-30:2018/Amd. 1:2022(E)
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ii
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ISO/IEC 14496-30:2018/Amd. 1:2022(E)
Information technology — Coding of audio-visual
objects —
Part 30:
Timed text and other visual overlays in ISO base media file
format
AMENDMENT 1: Timing improvements
Clause 3
Replace the 3.1.2 entry with
timed text stream
stream of content, which when decoded results in textual content, possibly containing internal timing
values, to be processed at a given presentation time and for a certain duration
4.2, second paragraph
Replace the second sentence of the second paragraph, "The rendering of the sample happens at the
composition time, taking into account edit lists if any, and for the whole sample duration, without
timing behaviour.", with:
The rendering of the sample happens at the presentation time, i.e. taking into account edit lists if any,
and for the sample duration, potentially trimmed by the edit list if any.
NOTE As defined in ISOBMFF, the presentation is driven by the presentation time. The composition time is
determined from the presentation time using the edit list (if present), and the sample active at that composition
time is then processed. This specification assumes that at a given presentation time, the renderer is provided
with the sample and the composition time, both of which correspond to the given presentation time.
5.3
Replace the entire subclause with:
This subclause defines processing of timing information for TTML documents carried in a TTML track.
The general timing processing defined in 4.2 applies, but specific aspects are refined in this subclause.
Timing processing is defined only for TTML documents in which ttp: timeBase is ‘media’. For other
values, timing processing behaviour is undefined and such documents should not be carried in TTML
tracks.
When the rendering of a sample happens, the TTML document in the sample is provided to the TTML
processor, together with the track composition time T of the sample and the sample composition
duration d. The TTML processor then uses the interval TT, +d together with the time coordinates
[ )
T produced by the “resolve timing” procedure, as defined in TTML, to determine which intermediate
{}
i
1
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ISO/IEC 14496-30:2018/Amd. 1:2022(E)
synchronic documents (ISDs) to present and for how long. Specifically, track composition time
tT∈+, Td results in TTML ISD i being presented, with tT∈ , T .
[ ) [ )
ii+1
NOTE 1 The fact that time coordinates produced by the TTML processor are interpreted as being on the
track composition timeline remains true in the case of segment files, defined in 14496-12. In other words, time
coordinates produced by a document stored in a sample of a segment are still relative to time 0 on the track
composition timeline and are not relative to the segment start.
The above concepts are illustrated in Table 1 and Table 2.
Table 1 — Example of a TTML track with six samples
Sample Composition Duration Payload
time
1 00:00:00 00:30:00
1-2 minutes
div>2 00:30:00 00:30:00
31-32 minutes
div>3 01:00:00 00:30:00
60-150 minutes p>
4 01:30:00 00:30:00
60-150 minutes p>
5 02:00:00 00:30:00
60-150 minutes
div>2
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ISO/IEC 14496-30:2018/Amd. 1:2022(E)
Table 1 (continued)
Sample Composition Duration Payload
time
6 02:30:00 00:30:00
150 minutes onwards
The sample composition times of the samples in Table 1 are 0 min, 30 min, 1 h, 1 h 30 min, 2 h, and
2 h 30 min, which correspond to the time at which the decoder processes the TTML content from that
sample. The text content in the payload of these samples reflects when that text will be displayed. For
example, the text “60-150 minutes” is expected to be shown between composition times 60 min and
150 min. The timing information in the TTML documents in these samples is not necessarily matching
the times in the text content (e.g. 00:00:00 to 04:00:00) precisely to illustrate the impact of storing the
content in ISOBMFF samples. Table 2 shows how each sample is processed to produce ISDs, and then
how these are clipped to the sample times for display. The ISDs excerpts in Table 2 are illustrative and
only focusing on timing aspects and content. Compliant TTML ISDs can need to include region elements.
Table 2 — ISD for the TTML track of Table 1
Sample ISD contents produced by TTML’s “re- ISD contents output from sample
solve timing” procedure and associated processing and associated time
time range range
1 00:00:00 to 00:01:00
Empty document
00:01:00 to 00:02:00 00:01:00 to 00:02:00
1-2 minutes
1-2 minutes
00:02:00 to Infinity 00:02:00 to 00:30:00
Empty document Empty document
2 00:30:00 to 00:31:00
Empty document
00:31:00 to 00:32:00 00:31:00 to 00:32:00
31-32 minutes
31-32 minutes
00:32:00 to Infinity 00:32:00 to 01:00:00
Empty document Empty document
3 00:00:00 to 04:00:00 01:00:00 to 01:30:00
60-150 minutes
60-150 minutes
04:00:00 to Infinity
Empty document
4 00:00:00 to 04:00:00 01:30:00 to 02:00:00
60-150 minutes
60-150 minutes
04:00:00 to Infinity
Empty document
5 02:00:00 to 02:30:00 02:00:00 to 02:30:00
60-150 minutes
60-150 minutes
02:30:00 to Infinity
Empty document
3
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ISO/IEC 14496-30:2018/Amd. 1:2022(E)
Table 2 (continued)
Sample ISD contents produced by TTML’s “re- ISD contents output from sample
solve timing” procedure and associated processing and associated time
time range range
6 02:30:00 to Infinity 02:30:00 to 03:00:00
150 minutes onwards
150 minutes onwards
When processing sample 1, following TTML’s “resolve timing” procedure, two ISDs are created: one
non-empty ISD ISD and one subsequent empty ISD ISD . However, because the time interval of ISD
1 2 1
starts after the sample timing interval, the sample processor can additionally output one more ISD,
corresponding to an empty document, to be displayed from the start of the track until the start of
ISD . ISD is to be displayed from the end of ISD until the sample composition end ti
...
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