QuickTime文件格式规范：多媒体交换的理想选择

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QuickTime File Format Specification (QTFF) 是一种专为数字多媒体数据存储设计的文件格式，它被广泛用于不同设备、应用程序和操作系统之间的媒体交换。这种格式的优势在于其灵活性和兼容性，能够支持各种类型的数据，包括音频、视频、图像和元数据等，这些都是多媒体内容的核心组成部分。该规范由 Apple Inc. 在 2004 年和 2007 年发布，版权全归 Apple 所有。根据版权协议，用户只能在个人计算机上存储文档供个人使用，并且可以打印文档副本，但必须保留 Apple 的版权声明。苹果的商标，如苹果 logo，以及特定键入组合（如 Option-Shift-K）的使用，如果没有事先书面许可，不得用于商业目的，否则可能构成商标侵权和不公平竞争，违反联邦和州法律。 QuickTime File Format Specification 不仅定义了文件的结构和组织方式，还包括了数据编码、解码、存储和检索的方法。对于软件开发者来说，这个规范提供了关键的信息，指导他们如何开发和实现与 QuickTime 兼容的应用程序，确保跨平台的无缝体验。开发者可以了解到文件头的详细结构，如时间戳、数据区段、元数据和压缩算法等，这些都是保证文件能够被正确解析和播放的关键元素。此外，该规范还强调了知识产权保护的重要性，所有关于技术的描述都受到法律保护，意味着开发者在利用这些技术时必须遵循相应的授权条款。这意味着，即使在开发基于 QuickTime 的应用程序时，也需要尊重苹果的技术所有权，避免无意中侵犯他人权益。 QuickTime File Format Specification 是一个核心的技术文档，对于开发人员来说，理解和遵守其规定是创建高效、兼容和合法的多媒体应用的基石。通过掌握这一规范，开发者能够确保他们的产品能够流畅地与 QuickTime 环境互动，满足用户的多元化需求。

Organization of This Document

This document begins with an overview of QuickTime atoms, then presents the structure of the

QuickTime file format in detail. This is followed by a series of code examples for manipulating a

QuickTime file using the QuickTime API. Finally, a number of related topics are described in a series

of appendixes. These include such topics as the QuickTime Image File format, the handling of metadata

when importing files into QuickTime, and details of the profile atom.

QuickTime files are described in general, rather than how they are supported on a specific computing

platform or in a specific programming language. As a result, the file format information is presented

in a tabular manner, rather than in coded data structures. Similarly, field names are presented in

English rather than as programming language tags. Furthermore, to the extent possible, data types

are described generically. For example, this book uses “32-bit signed integer” rather than “long” to

define a 32-bit integer value.

QuickTime files are used to store QuickTime movies, as well as other data. If you are writing an

application that parses QuickTime files, you should recognize that there may be non-movie data in

the files.

Licensing Information

The QuickTime File Format Specification is provided for informational purposes. Apple may have

patents, patent applications, trademarks, copyrights, or other intellectual property rights covering

subject matter in this document. The furnishing of this document does not give you a license to any

patents, trademarks, copyrights, or other intellectual property.

Important: For more information about licensing the QuickTime File Format, contact: Apple, Inc.,

Software Licensing Department, 12545 Riata Vista Circle, MS 198 3-SWL, Austin, TX 78727. Email

Address: sw.license@apple.com

Special Fonts

All code listings, reserved words, and the names of actual data structures, constants, fields, parameters,

and routines are shown in Letter Gothic (this is Letter Gothic).

Words that appear in boldface are key terms or concepts and are defined in the glossary.

Updates to This Specification

For updates or changes to this specification, go to the QuickTime documentation site at

QuickTime Reference Library

Organization of This Document

INTRODUCTION

Introduction to QuickTime File Format Specification

Note: An atom, as described in this document, is functionally identical to a box, as described in the

ISO specifications for MPEG-4 and JPEG-2000. An atom that includes version and flags fields is

functionally identical to a full box as defined in those specifications.

Atom types are specified by a 32-bit unsigned integer, typically interpreted as a four-character ASCII

code. Apple, Inc. reserves all four-character codes consisting entirely of lowercase letters. Unless

otherwise stated, all data in a QuickTime movie is stored in big-endian byte ordering, also known as

network byte ordering, in which the most significant bytes are stored and transmitted first.

Atoms are hierarchical in nature. That is, one atom can contain other atoms, which can contain still

others, and so on. This hierarchy is sometimes described in terms of a parent, children, siblings,

grandchildren, and so on. An atom that contains other atoms is called a container atom. The parent

atom is the container atom exactly one level above a given atom in the heirarchy.

For example, a movie atom contains several different kinds of atoms, including one track atom for

each track in the movie. The track atoms, in turn, contain one media atom each, along with other

atoms that define other track characteristics. The movie atom is the parent atom of the track atoms.

The track atoms are siblings. The track atoms are parent atoms of the media atoms. The movie atom

is not the parent of the media atoms, because it is more than one layer above them in the hierarchy.

An atom that does not contain other atoms is called a leaf atom, and typically contains data as one

or more fields or tables. Some leaf atoms act as flags or placeholders, however, and contain no data

beyond their size and type fields.

The format of the data stored within a given atom cannot always be determined by the type field of

the atom alone; the type of the parent atom may also be significant. In other words, a given atom type

can contain different kinds of information depending on its parent atom. For example, the profile

atom inside a movie atom contains information about the movie, while the profile atom inside a track

atom contains information about the track. This means that all QuickTime file readers must take into

consideration not only the atom type, but also the atom’s containment hierarchy.

Atom Layout

Figure 1-1 (page 21) shows the layout of a sample atom. Each atom carries its own size and type

information as well as its data. Throughout this document, the name of a container atom (an atom

that contains other atoms, including other container atoms) is printed in a gray box, and the name of

a leaf atom (an atom that contains no other atoms) is printed in a white box. Leaf atoms contain data,

usually in the form of tables.

Atoms

CHAPTER 1

Overview of QTFF

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