---
title: Subtitle sample description
framework: quicktime-file-format
role: symbol
role_heading: Atom
path: quicktime-file-format/subtitle_sample_description
---

# Subtitle sample description

An atom that defines how to interpret subtitle media data.

## Overview

Overview The subtitle sample description contains information that defines how to interpret subtitle media data. This sample description is based on the standard sample description header, as described in Sample description atom ('stsd'). note: Only one sample description is permitted in a 'sbtl' track. The data format field in the sample description is currently always set to 'tx3g'. Unrecognized data formats should be ignored. The text media described here is based on the text box defined in the 3GPP Timed Text specification but provides a different track type and media handler designed specifically for subtitles. The subtitle media handler adds some of its own fields to the sample description.

## Topics

### Data fields

- [Display flags](quicktime-file-format/subtitle_sample_description/display_flags.md)
- [Reserved](quicktime-file-format/subtitle_sample_description/reserved.md)
- [Reserved](quicktime-file-format/subtitle_sample_description/reserved2.md)
- [Reserved](quicktime-file-format/subtitle_sample_description/reserved3.md)
- [Default text box](quicktime-file-format/subtitle_sample_description/default_text_box.md)
- [Reserved](quicktime-file-format/subtitle_sample_description/reserved4.md)
- [Font identifier](quicktime-file-format/subtitle_sample_description/font_identifier.md)
- [Font face](quicktime-file-format/subtitle_sample_description/font_face.md)
- [Font size](quicktime-file-format/subtitle_sample_description/font_size.md)
- [Foreground color](quicktime-file-format/subtitle_sample_description/foreground_color.md)
- [Font table](quicktime-file-format/subtitle_sample_description/font_table.md)

## See Also

### Storing subtitles

- [Font table atom ('ftab')](quicktime-file-format/font_table_atom.md)
- [Subtitle sample data](quicktime-file-format/subtitle_sample_data.md)
- [Subtitle style atom ('styl')](quicktime-file-format/subtitle_style_atom.md)
- [Text box atom ('tbox')](quicktime-file-format/text_box_atom.md)
- [Subtitle track header size and placement](quicktime-file-format/subtitle_track_header_size_and_placement.md)
- [Referencing a related forced subtitle track](quicktime-file-format/referencing_a_related_forced_subtitle_track.md)