Apple QuickTime文件格式2010年更新

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"快速时间文件格式规范，2010年5月版，由Apple公司发布，相较于2007年的版本有所更新，提供更清晰的视频体验。该文档主要涉及QuickTime MOV文件格式的详细信息，包括数据管理和文件管理等核心内容。" QuickTime文件格式，是Apple公司开发的一种多媒体容器格式，它被广泛用于存储音频、视频和字幕等数据。2010年5月发布的这个新版本，对原有的2007版本进行了优化，以提供更为清晰的视频质量，这可能涉及到编码算法的改进、压缩效率的提升以及支持更多新的编解码器。 QuickTime File Format Specification是官方的技术文档，详细阐述了QuickTime文件的内部结构和操作方式。这份文档涵盖了多个关键领域，例如： 1. **数据管理**：这部分内容可能包含了如何组织和存储媒体数据的详细信息，包括时间线、轨道管理和元数据的处理。数据管理确保了文件的高效性和兼容性。 2. **文件管理**：文件管理部分可能涉及文件的创建、打开、读取、写入和保存过程，以及错误处理和文件完整性检查。这些机制对于确保文件在不同环境下的稳定性和可靠性至关重要。 3. **格式细节**：QuickTime MOV文件格式支持多种类型的媒体数据，如MPEG-4、H.264视频和AAC音频等。2010年的版本可能增加了对当时新兴编码技术的支持，以适应不断发展的多媒体需求。 4. **版权和许可**：文档中提到了Apple的版权声明，表明虽然可以个人用途存储和打印文档，但未经许可，不得用于商业目的。这强调了Apple对其知识产权的保护。 5. **技术知识产权**：Apple保留了所有与文档描述技术相关的知识产权，这意味着第三方在使用QuickTime格式时需要遵循特定的许可协议。这份2010年的QuickTime文件格式规范，对于开发者、内容创作者和系统管理员来说，是一个重要的参考资料，他们可以通过此文档了解如何与QuickTime文件进行交互，以及如何利用新的特性来优化多媒体内容的创建和分发。随着技术的不断进步，这种版本更新确保了QuickTime格式能够保持其在多媒体领域的领先地位。

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 code voice.

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

and click the File Format Specification link.

For More Information

For information about membership in Apple’s developer program and developer technical support, you

should go to this URL:

Apple Developer

For information on registering signatures, file types, and other technical information, contact

Licensing Information

INTRODUCTION

Introduction to QuickTime File Format Specification

QuickTime movies are stored on disk, using two basic structures for storing information: atoms (also known

as simple atoms or classic atoms), and QT atoms. To understand how QuickTime movies are stored, you need

to understand the basic atom structures described in this chapter. Most atoms you encounter in the QuickTime

File Format are simple or classic atoms. Both simple atoms and QT atoms, however, allow you to construct

arbitrarily complex hierarchical data structures. Both also allow your application to ignore data they don’t

understand.

Media Description

A QuickTime file stores the description of its media separately from the media data. The description is called

the movie resource, movie atom, or simply the movie, and contains information such as the number of tracks,

the video compression format, and timing information. The movie resource also contains an index describing

where all the media data is stored.

The media data is the actual sample data, such as video frames and audio samples, used in the movie. The

media data may be stored in the same file as the QuickTime movie, in a separate file, in multiple files, in

alternate sources such as databases or real-time streams, or in some combination of these.

Atoms

The basic data unit in a QuickTime file is the atom. Each atom contains size and type fields that precede any

other data. The size field indicates the total number of bytes in the atom, including the size and type fields.

The type field specifies the type of data stored in the atom and, by implication, the format of that data. In

some cases, the size and type fields are followed by a version field and a flags field. An atom with these

version and flags fields is sometimes called a full atom.

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 hierarchy.

Media Description 19

CHAPTER 1

Overview of QTFF

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 20) 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.

Figure 1-1 A sample atom

Container atom

Atom size

Atom type

Container atom

Leaf atom

Atom size

Atom type

Atom data

Atom size

Atom type

A leaf atom, as shown in Figure 1-1 (page 20), simply contains a series of data fields accessible by offsets.

Atoms within container atoms do not generally have to be in any particular order, unless such an order is

specifically called out in this document. One such example is the handler description atom, which must come

before the data being handled. For example, a media handler description atom must come before a media

information atom, and a data handler description atom must come before a data information atom.

Atoms

CHAPTER 1

Overview of QTFF

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