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.

Timed text tracks should use suitable language in the mdhd box.

Samples with a size of zero are not used.

hdlr is subt for ttml tracks.

TTML tracks shall use the XMLSubtitleSampleEntry the namespace shall be set to atleast one unique namespace.

The scheme_location field should be set.

Every sample is a sync sample, sync sample table not present.

VTT Sample boxes shall not contain CR or LF characters, or trailing CRLF sequences.

Timed text uses nmhd and hdlr is ‘text’.

All samples are sync samples, sync sample table is not used.

vtt sample entry is used and correct media handler and nmhd.

In WVTTSampleEntry, WebVTT configuration must occur, containing webvtt file header.

webvtt source label box should occur in the sample entry.

Each sample is either one VTTCueEmptyCueBox or one or more VTTCueBoxes.

If a cue has WevVTT cue settings they are placed in cue settings box without leading space.

There is no CueSourceIDBox in samples if there is no source label.