---
title: Additional data table
framework: quicktime-file-format
role: symbol
role_heading: Data field
path: quicktime-file-format/hint_track_sample_description/additional_data_table
---

# Additional data table

A table of variable length containing additional information.

## Overview

Overview Additional information is formatted as a series of tagged entries. This field always contains a tagged entry indicating the RTP time scale for RTP data. All other tagged entries are optional. Three data tags are currently defined for RTP data. One tag is defined for use with any type of data. You can create additional tags. Tags are identified using four-character codes. Tags using all lowercase letters are reserved by Apple. Ignore any tagged data you do not understand. Table entries are structured like atoms. The structure of table entries is shown in the following table.  |  |   |  |   |  |   |  |  Tagged entries for the ’rtp ’ data format are defined as follows:

## See Also

### Data fields

- [Size](quicktime-file-format/hint_track_sample_description/size.md)
- [Data format](quicktime-file-format/hint_track_sample_description/data_format.md)
- [Reserved](quicktime-file-format/hint_track_sample_description/reserved.md)
- [Data reference index](quicktime-file-format/hint_track_sample_description/data_reference_index.md)
- [Hint track version](quicktime-file-format/hint_track_sample_description/hint_track_version.md)
- [Last compatible hint track version](quicktime-file-format/hint_track_sample_description/last_compatible_hint_track_version.md)
- [Max packet size](quicktime-file-format/hint_track_sample_description/max_packet_size.md)