---
title: Dictionary Keys
framework: Core Media
role: collectionGroup
role_heading: API Collection
path: coremedia/cmtimerange-dictionary-keys
---

# Dictionary Keys

Keys to use when working with dictionary representations of a time range.

## Overview

Overview To convert a CMTimeRange to and from a CFDictionary, see CMTimeRangeCopyAsDictionary(_:allocator:) and CMTimeRangeMakeFromDictionary(_:).

## Topics

### Constants

- [kCMTimeRangeStartKey](coremedia/kcmtimerangestartkey.md)
- [kCMTimeRangeDurationKey](coremedia/kcmtimerangedurationkey.md)

## See Also

### Constants

- [Pre-Specified Time Ranges](coremedia/pre-specified-time-ranges.md)