---
title: Sample atoms
framework: quicktime-file-format
role: collectionGroup
role_heading: API Collection
path: quicktime-file-format/sample_atoms
---

# Sample atoms

Atoms that describe samples, which are single elements in a sequence of time-ordered data.

## Overview

Overview QuickTime stores media data in samples. A sample is a single element in a sequence of time-ordered data. Samples are stored in the media, and they may have varying durations. Samples are stored in a series of chunks in a media. Chunks are a collection of data samples in a media that allow optimized data access. A chunk may contain one or more samples. Chunks in a media may have different sizes, and the individual samples within a chunk may have different sizes from one another, as shown in the following figure.

One way to describe a sample is to use a sample table atom. The sample table atom acts as a storehouse of information about the samples and contains a number of different types of atoms. The various atoms contain information that allows the media handler to parse the samples in the proper order. This approach enforces an ordering of the samples without requiring that the sample data be stored sequentially with respect to movie time in the actual data stream.

## Topics

### Describing samples

- [Sample table atom ('stbl')](quicktime-file-format/sample_table_atom.md)
- [Seeking with a QuickTime file](quicktime-file-format/seeking_with_a_quicktime_file.md)
- [Sample description atom ('stsd')](quicktime-file-format/sample_description_atom.md)
- [Time-to-sample atom ('stts')](quicktime-file-format/time-to-sample_atom.md)
- [Creating video tracks at 30 frames per second](quicktime-file-format/creating_video_tracks_at_30_frames_per_second.md)
- [Creating video tracks at 29.97 frames per second](quicktime-file-format/creating_video_tracks_at_2997_frames_per_second.md)
- [Creating sound tracks at 44.1 kHz](quicktime-file-format/creating_sound_tracks_at_441_khz.md)
- [Composition offset atom ('ctts')](quicktime-file-format/composition_offset_atom.md)
- [Composition shift least greatest atom ('cslg')](quicktime-file-format/composition_shift_least_greatest_atom.md)
- [Using composition offset and composition shift least greatest atoms](quicktime-file-format/using_composition_offset_and_composition_shift_least_greatest_atoms.md)
- [Sync sample atom ('stss')](quicktime-file-format/sync_sample_atom.md)
- [Partial sync sample atom ('stps')](quicktime-file-format/partial_sync_sample_atom.md)
- [Sample-to-chunk atom ('stsc')](quicktime-file-format/sample-to-chunk_atom.md)
- [Referencing two data files with a single track](quicktime-file-format/referencing_two_data_files_with_a_single_track.md)
- [Sample size atom ('stsz')](quicktime-file-format/sample_size_atom.md)
- [Chunk offset atom ('stco')](quicktime-file-format/chunk_offset_atom.md)
- [Sample dependency flags atom ('sdtp')](quicktime-file-format/sample_dependency_flags_atom.md)
- [Using sample atoms](quicktime-file-format/using_sample_atoms.md)

## See Also

### Movies

- [Movie atoms](quicktime-file-format/movie_atoms.md)
- [Track atoms](quicktime-file-format/track_atoms.md)
- [Media atoms](quicktime-file-format/media_atoms.md)
- [Structuring movie data and features](quicktime-file-format/structuring_movie_data_and_features.md)