Timed Text Formatting
Validator implements checks to assert conformance to ISO/IEC 14496-30. This is the MP4 subtitle/timed text format.
Table of Contents
Should Fix: 14496-12 8.3.2.3 and ISO 14496-30 4.1
tkhd: timed text are normally stacked in front of associated visual tracks layer should therefore be -1.
Should Fix: 14496-30 4.2
Timed text tracks should use suitable language in the mdhd box.
Must Fix: ISO 14496-30 4.2
Samples with a size of zero are not used.
Must Fix: 14496-30 5.4
hdlr is subt for ttml tracks.
Must Fix: 14496-30 Sample Entry
TTML tracks shall use the XMLSubtitleSampleEntry the namespace shall be set to atleast one unique namespace.
Should Fix: 14496-30 5.5 scheme location
The scheme_location field should be set.
Should Fix: 14496-30 5.6 sync samples
Every sample is a sync sample, sync sample table not present.
Must Fix: 14496-30 6.1
VTT Sample boxes shall not contain CR or LF characters, or trailing CRLF sequences.
Must Fix: 14496-30 6.2
Timed text uses nmhd and hdlr is ‘text’.
Must Fix: 14496-30 6.3 sync samples
All samples are sync samples, sync sample table is not used.
Must Fix: 14496-30 6.4 Sample Entry
vtt sample entry is used and correct media handler and nmhd.
Must Fix: 14496-30 6.5 WVTT Sample Entry
In WVTTSampleEntry, WebVTT configuration must occur, containing webvtt file header.
Should Fix: 14496-30 6.5 source label
webvtt source label box should occur in the sample entry.
Must Fix: 14496-30 6.5 Sample
Each sample is either one VTTCueEmptyCueBox or one or more VTTCueBoxes.
Should Fix: 14496-30 6.6 Cue settings
If a cue has WevVTT cue settings they are placed in cue settings box without leading space.
Should Fix: 14496-30 6.6 Cue Source ID
There is no CueSourceIDBox in samples if there is no source label.