---
title: "Media atom ('mdia')"
framework: quicktime-file-format
role: symbol
role_heading: Atom
path: quicktime-file-format/media_atom
---

# Media atom ('mdia')

An atom that describes and defines a track’s media type and sample data.

## Overview

Overview The media atom has an atom type of 'mdia'. It must contain a media header atom ('mdhd'), and it can contain a handler reference ('hdlr') atom, media information ('minf') atom, and user data ('udta') atom. note: Do not confuse the media atom ('mdia') with the media data atom ('mdat'). The media atom contains only references to media data; the media data atom contains the actual media samples. The layout of a media atom is as follows.  |   |   |   |   |   |   |   |  ‡ denotes required atom.

## Topics

### Data fields

- [Size](quicktime-file-format/media_atom/size.md)
- [Type](quicktime-file-format/media_atom/type.md)
- [Media header atom](quicktime-file-format/media_atom/media_header_atom.md)
- [Extended language tag atom](quicktime-file-format/media_atom/extended_language_tag_atom.md)
- [Handler reference atom](quicktime-file-format/media_atom/handler_reference_atom.md)
- [Media information atom](quicktime-file-format/media_atom/media_information_atom.md)
- [User data atom](quicktime-file-format/media_atom/user_data_atom.md)

## See Also

### Describing media

- [Media header atom ('mdhd')](quicktime-file-format/media_header_atom.md)
- [Extended language tag atom ('elng')](quicktime-file-format/extended_language_tag_atom.md)
- [Handler reference atom ('hdlr')](quicktime-file-format/handler_reference_atom.md)
- [Media information atoms](quicktime-file-format/media_information_atoms.md)
- [Video media information atom ('minf')](quicktime-file-format/video_media_information_atom.md)
- [Video media information header atom ('vmhd')](quicktime-file-format/video_media_information_header_atom.md)
- [Sound media information atom ('minf')](quicktime-file-format/sound_media_information_atom.md)
- [Sound media information header atom ('smhd')](quicktime-file-format/sound_media_information_header_atom.md)
- [Base media information atom ('minf')](quicktime-file-format/base_media_information_atom.md)
- [Base media information header atom ('gmhd')](quicktime-file-format/base_media_information_header_atom.md)
- [Base media info atom ('gmin')](quicktime-file-format/base_media_info_atom.md)
- [Data information atom ('dinf')](quicktime-file-format/data_information_atom.md)
- [Data reference atom](quicktime-file-format/media_data_reference_atom.md)