---
title: "Sample size atom ('stsz')"
framework: quicktime-file-format
role: symbol
role_heading: Atom
path: quicktime-file-format/sample_size_atom
---

# Sample size atom ('stsz')

An atom you use to specify the size of each sample in the media.

## Overview

Overview Sample size atoms have an atom type of 'stsz'. The sample size atom contains the sample count and a table giving the size of each sample. This allows the media data itself to be unframed. The total number of samples in the media is always indicated in the sample count. If the default size is indicated, then no table follows. The layout of a sample size atom is as follows.  |   |   |   |   |   |   |   |

## Topics

### Data fields

- [Size](quicktime-file-format/sample_size_atom/size.md)
- [Type](quicktime-file-format/sample_size_atom/type.md)
- [Version](quicktime-file-format/sample_size_atom/version.md)
- [Flags](quicktime-file-format/sample_size_atom/flags.md)
- [Sample size](quicktime-file-format/sample_size_atom/sample_size.md)
- [Number of entries](quicktime-file-format/sample_size_atom/number_of_entries.md)
- [Sample size table](quicktime-file-format/sample_size_atom/sample_size_table.md)

## See Also

### 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)
- [Chunk offset atom ('stco')](quicktime-file-format/chunk_offset_atom.md)