Fragmented MP4格式详解
FMP4（Fragmented MP4）是一种用于通过互联网传输音频和视频内容的文件格式。 它是 MP4 文件格式的扩展，支持以小片段形式传送媒体内容。
以下是 FMP4 格式中主要信息字段的概述：
框：FMP4 文件由一系列框组成，其中包含有关媒体内容的元数据。 每个框都有一个唯一标识符和一个指示框大小的大小字段。
轨道：轨道框包含媒体内容中特定轨道的信息，例如轨道编号、轨道类型（音频或视频）以及媒体数据的格式。
媒体：媒体框包含有关媒体内容类型的信息，例如音频或视频，以及用于对数据进行编码的编解码器。
样本：样本框包含有关媒体数据各个样本的信息，包括样本持续时间、样本大小和样本合成时间。
片段：片段框包含有关媒体数据各个片段的信息，包括片段的持续时间和片段在文件中的位置。
初始化段：初始化段包含有关文件结构的信息，包括第一个片段的位置和片段的大小。
Index：索引框包含文件中片段的索引，用于播放时定位特定片段。
比特率：FMP4 文件的比特率是每单位时间传输的数据量，通常以比特每秒 (bps) 为单位。
加密：FMP4 支持使用加密来保护媒体内容免遭未经授权的访问。 加密密钥通常存储在一个单独的文件中，称为密钥文件。
流媒体协议：FMP4 通常与 HTTP 实时流媒体 (HLS) 和基于 HTTP 的动态自适应流媒体 (DASH) 等流媒体协议一起使用，这些协议能够以可扩展且高效的方式通过 Internet 交付媒体内容。
时间戳：FMP4 支持在播放过程中使用时间戳来同步音频和视频内容。 时间戳通常基于每个样本的媒体呈现时间 (PTS) 和解码时间 (DTS)。
元数据：FMP4 支持在文件中包含元数据，例如有关内容创建者、创建日期和版权所有者的信息。
碎片化：FMP4 允许将媒体内容分成更小的片段，从而可以更有效地通过互联网传送内容。 片段的大小可以根据应用程序的需要而变化。
兼容性：FMP4 与多种媒体播放器和流媒体协议兼容，这使其成为通过互联网传送媒体内容的热门选择。
编辑：FMP4 支持对媒体内容进行编辑，例如剪切和拼接视频片段，而无需重新编码整个文件。
定时元数据：FMP4 允许在文件中包含定时元数据，它可用于提供有关媒体内容的附加信息，例如章节标记、字幕和备用音轨。
H.264 和 AAC：FMP4 通常使用 H.264 视频编解码器和高级音频编码 (AAC) 音频编解码器，媒体播放器和流媒体协议广泛支持它们。
碎片化交付：FMP4 允许以碎片化的方式交付媒体内容，从而可以更高效地通过互联网交付内容，并降低播放期间缓冲的风险。
流媒体选项：FMP4 支持一系列流媒体选项，包括实时流媒体、视频点播和渐进式下载。 这种灵活性使其适用于广泛的用例，从大型现场活动到点播视频播放。
自适应比特率：FMP4 支持自适应比特率流，这意味着可以即时调整媒体内容的质量以匹配可用带宽和设备功能。 这有助于确保用户获得流畅且不间断的播放体验。
碎片化交付：FMP4 允许以碎片化的方式交付媒体内容，从而可以更高效地通过互联网交付内容，并降低播放期间缓冲的风险。
多音轨和字幕：FMP4 支持在一个文件中包含多个音轨和字幕，这允许观众在播放过程中选择他们喜欢的语言或字幕。
隐藏式字幕：FMP4 支持隐藏式字幕，允许在媒体内容中为失聪或有听力障碍的观众添加文本字幕。
DRM：FMP4 支持数字版权管理 (DRM)，允许内容所有者保护他们的内容免遭未经授权的访问和分发。
编解码器和容器：FMP4 是一种容器格式，支持一系列音频和视频编解码器，包括 H.264、AAC 和 HEVC。 这使得它适用于广泛的媒体内容和设备。
碎片化交付：FMP4 允许以碎片化的方式交付媒体内容，从而可以更高效地通过互联网交付内容，并降低播放期间缓冲的风险。
元数据：FMP4 支持在文件中包含元数据，例如有关内容创建者、创建日期和版权所有者的信息。
章节标记：FMP4 允许在媒体内容中包含章节标记，这使观众能够快速导航到视频中的特定点。
交互性：FMP4 支持交互性功能，例如可点击按钮和交互式覆盖，可以增强观看者的体验并提供有关内容的附加信息。
碎片化交付：FMP4 允许以碎片化的方式交付媒体内容，从而可以更高效地通过互联网交付内容，并降低播放期间缓冲的风险。
兼容性：FMP4 与多种媒体播放器和流媒体协议兼容，这使其成为通过互联网传送媒体内容的热门选择。
字幕格式：FMP4 支持多种字幕格式，包括 WebVTT、TTML 和 SRT，这使得在媒体内容中添加字幕变得容易。
流媒体协议：FMP4 通常与 HTTP 实时流媒体 (HLS) 和基于 HTTP 的动态自适应流媒体 (DASH) 等流媒体协议一起使用，这些协议能够以可扩展且高效的方式通过 Internet 交付媒体内容。
碎片化交付：FMP4 允许以碎片化的方式交付媒体内容，从而可以更高效地通过互联网交付内容，并降低播放期间缓冲的风险。
数据流：除了音频和视频内容外，FMP4 还支持文本和图像等数据流。 这使得创建更具交互性和吸引力的媒体体验成为可能。
加密：FMP4 支持媒体内容加密，有助于防止盗版和未经授权的访问。
字幕：FMP4 支持为听障人士提供字幕，这有助于让更广泛的受众更容易访问媒体内容。
多语言支持：FMP4 支持包含多种不同语言的音频和字幕轨道，这有助于使讲不同语言的观众更容易访问媒体内容。
与广告网络集成：FMP4 可以轻松与广告网络集成，使内容所有者能够通过广告从他们的媒体内容中获利。
与分析集成：FMP4 可以与分析平台集成，允许内容所有者跟踪观众参与度并深入了解观众行为。
可扩展性：FMP4 的设计具有高度可扩展性，这意味着它可用于在不牺牲质量或性能的情况下同时向大量观众提供媒体内容。
低延迟：FMP4支持低延迟流，适合需要实时交互的应用，如体育直播、视频会议等。
自适应流式传输：FMP4 支持自适应流式传输，可以根据观众的可用带宽和设备功能实时调整媒体内容的质量。 这有助于确保观众获得流畅且不间断的播放体验。
与硬件的兼容性：FMP4 得到硬件设备的广泛支持，包括智能手机、平板电脑和智能电视，这使其成为将媒体内容传送到各种设备的热门选择。
更小的文件大小：FMP4 支持分段交付，这允许以更小的文件大小交付媒体内容，减少交付内容所需的带宽量，并使其更容易通过互联网流式传输。
快速搜索：FMP4 支持快速搜索，允许观众快速导航到视频中的特定点，而不会经历长时间的缓冲或延迟。
减少缓冲：FMP4 对分段传输、自适应流媒体和低延迟流媒体的支持有助于减少缓冲并改善整体观看体验。
服务器端广告插入：FMP4 支持服务器端广告插入，可以更高效地投放广告并降低广告拦截的风险。
高品质音频：FMP4 支持高品质音频，包括 5.1 和 7.1 环绕声，增强了观众的音频体验。
广泛的应用：FMP4可用于广泛的应用，包括直播、视频点播和交互式视频体验。
低成本：FMP4 是一种成本相对较低的解决方案，用于通过互联网传送媒体内容，这使其成为各种规模的企业和组织的有吸引力的选择。
易于使用：FMP4 易于使用和实施，减少了实习生启动和运行媒体内容所需的时间和资源等。
基于标准：FMP4 基于开放标准，确保与广泛的设备和平台兼容。
与内容管理系统集成：FMP4 可以很容易地与内容管理系统集成，让内容所有者可以轻松管理和分发他们的媒体内容。
带内事件信令：FMP4 支持带内事件信令，可以交付交互式内容并允许内容所有者收集有关观众参与度的数据。
实时转码：FMP4 支持实时转码，可以对媒体内容进行实时编码，减少对预编码内容的需求，实现更快的直播流传输。
与内容分发网络集成：FMP4 可轻松与内容分发网络集成，确保向全球观众快速可靠地分发媒体内容。
范围广泛的编解码器：FMP4 支持范围广泛的编解码器，包括 H.264、HEVC 和 VP9，这使内容所有者能够以尽可能高的质量交付媒体内容。
广泛的流媒体协议：FMP4 支持广泛的流媒体协议，包括 HTTP Live Streaming (HLS)、Dynamic Adaptive Streaming over HTTP (DASH) 和 Smooth Streaming，确保与广泛的设备和平台兼容。
互操作性：FMP4 专为互操作性而设计，这意味着以 FMP4 格式编码的媒体内容可以在广泛的设备和平台上播放，而不会出现任何兼容性问题。
字幕和隐藏式字幕：FMP4 支持在媒体内容中包含字幕和隐藏式字幕，这增强了有听力障碍或说不同语言的观众对内容的可访问性。
数字版权管理 (DRM)：FMP4 支持各种 DRM 技术，允许内容所有者保护他们的内容免遭未经授权的分发和盗版。
动态打包：FMP4支持动态打包，允许媒体内容根据观看者的设备和可用带宽实时动态打包，确保最高质量的观看体验。
在特定时间插入广告：FMP4 支持在视频中的特定时间插入广告，这使内容所有者能够更有效地从他们的内容中获利。
用户参与跟踪：FMP4 支持用户参与跟踪，允许内容所有者收集有关观众行为和偏好的数据，使他们能够优化内容并提高参与度。
与分析平台集成：FMP4 可以轻松与分析平台集成，让内容所有者能够跟踪观众的参与度并衡量其内容的有效性。
降低存储成本：FMP4 支持分段交付和动态打包，有助于降低媒体内容的存储成本，因为只有必要的片段才会存储在服务器上。
FMP4 (Fragmented MP4) is a file format used for streaming audio and video content over the internet. It is an extension of the MP4 file format and supports the delivery of media content in small fragments.
Here is an overview of the main fields of information in the FMP4 format:
Box: The FMP4 file is made up of a series of boxes, which contain metadata about the media content. Each box has a unique identifier and a size field that indicates the size of the box.
Track: The track box contains information about a specific track in the media content, such as the track number, track type (audio or video), and the format of the media data.
Media: The media box contains information about the type of media content, such as audio or video, and the codecs used to encode the data.
Sample: The sample box contains information about the individual samples of media data, including the sample duration, the sample size, and the sample composition time.
Fragment: The fragment box contains information about the individual fragments of media data, including the duration of the fragment and the location of the fragment in the file.
Initialization segment: The initialization segment contains information about the structure of the file, including the location of the first fragment and the size of the fragments.
Index: The index box contains an index of the fragments in the file, which is used to locate specific fragments during playback.
Bitrate: The bitrate of an FMP4 file is the amount of data transmitted per unit of time, typically measured in bits per second (bps).
Encryption: FMP4 supports the use of encryption to protect the media content from unauthorized access. The encryption keys are typically stored in a separate file, known as a key file.
Streaming protocols: FMP4 is commonly used with streaming protocols such as HTTP Live Streaming (HLS) and Dynamic Adaptive Streaming over HTTP (DASH), which enable the delivery of media content over the internet in a scalable and efficient manner.
Timestamps: FMP4 supports the use of timestamps to synchronize audio and video content during playback. Timestamps are typically based on the media presentation time (PTS) and the decode time (DTS) of each sample.
Metadata: FMP4 supports the inclusion of metadata in the file, such as information about the creator of the content, the date of creation, and the copyright holder.
Fragmentation: FMP4 allows media content to be divided into smaller fragments, which enables more efficient delivery of the content over the internet. The size of the fragments can be varied depending on the needs of the application.
Compatibility: FMP4 is compatible with a wide range of media players and streaming protocols, which makes it a popular choice for delivering media content over the internet.
Editing: FMP4 supports the editing of media content, such as cutting and splicing video segments, without the need for re-encoding the entire file.
Timed metadata: FMP4 allows timed metadata to be included in the file, which can be used to provide additional information about the media content, such as chapter markers, subtitles, and alternate audio tracks.
H.264 and AAC: FMP4 typically uses the H.264 video codec and the Advanced Audio Coding (AAC) audio codec, which are widely supported by media players and streaming protocols.
Fragmented delivery: FMP4 allows media content to be delivered in a fragmented manner, which enables more efficient delivery of the content over the internet and reduces the risk of buffering during playback.
Streaming options: FMP4 supports a range of streaming options, including live streaming, video-on-demand, and progressive download. This flexibility makes it suitable for a wide range of use cases, from large-scale live events to on-demand video playback.
Adaptive bitrate: FMP4 supports adaptive bitrate streaming, which means that the quality of the media content can be adjusted on-the-fly to match the available bandwidth and device capabilities. This helps to ensure a smooth and uninterrupted playback experience for the user.
Fragmented delivery: FMP4 allows media content to be delivered in a fragmented manner, which enables more efficient delivery of the content over the internet and reduces the risk of buffering during playback.
Multiple audio and subtitle tracks: FMP4 supports the inclusion of multiple audio and subtitle tracks in a single file, which allows viewers to choose their preferred language or subtitles during playback.
Closed captioning: FMP4 supports closed captioning, which allows for the inclusion of text captions in the media content for viewers who are deaf or hard-of-hearing.
DRM: FMP4 supports digital rights management (DRM), which allows content owners to protect their content from unauthorized access and distribution.
Codecs and containers: FMP4 is a container format that supports a range of audio and video codecs, including H.264, AAC, and HEVC. This makes it suitable for a wide range of media content and devices.
Fragmented delivery: FMP4 allows media content to be delivered in a fragmented manner, which enables more efficient delivery of the content over the internet and reduces the risk of buffering during playback.
Metadata: FMP4 supports the inclusion of metadata in the file, such as information about the creator of the content, the date of creation, and the copyright holder.
Chapter markers: FMP4 allows for the inclusion of chapter markers in the media content, which enables viewers to quickly navigate to specific points in the video.
Interactivity: FMP4 supports interactivity features, such as clickable buttons and interactive overlays, which can enhance the viewer's experience and provide additional information about the content.
Fragmented delivery: FMP4 allows media content to be delivered in a fragmented manner, which enables more efficient delivery of the content over the internet and reduces the risk of buffering during playback.
Compatibility: FMP4 is compatible with a wide range of media players and streaming protocols, which makes it a popular choice for delivering media content over the internet.
Subtitle formats: FMP4 supports a range of subtitle formats, including WebVTT, TTML, and SRT, which makes it easy to include subtitles in the media content.
Streaming protocols: FMP4 is commonly used with streaming protocols such as HTTP Live Streaming (HLS) and Dynamic Adaptive Streaming over HTTP (DASH), which enable the delivery of media content over the internet in a scalable and efficient manner.
Fragmented delivery: FMP4 allows media content to be delivered in a fragmented manner, which enables more efficient delivery of the content over the internet and reduces the risk of buffering during playback.
Data streaming: FMP4 supports the streaming of data, such as text and images, in addition to audio and video content. This makes it possible to create more interactive and engaging media experiences.
Encryption: FMP4 supports encryption of media content, which helps to protect against piracy and unauthorized access.
Captioning: FMP4 supports captioning for the hearing-impaired, which helps to make media content more accessible to a wider audience.
Multi-language support: FMP4 supports the inclusion of multiple audio and subtitle tracks in different languages, which helps to make media content more accessible to viewers who speak different languages.
Integration with ad networks: FMP4 can be easily integrated with ad networks, which enables content owners to monetize their media content through advertising.
Integration with analytics: FMP4 can be integrated with analytics platforms, which allows content owners to track viewer engagement and gain insights into viewer behavior.
Scalability: FMP4 is designed to be highly scalable, which means it can be used to deliver media content to large numbers of viewers simultaneously without sacrificing quality or performance.
Low latency: FMP4 supports low-latency streaming, which makes it suitable for applications that require real-time interaction, such as live sports broadcasts and video conferencing.
Adaptive streaming: FMP4 supports adaptive streaming, which enables the quality of the media content to be adjusted in real-time based on the viewer's available bandwidth and device capabilities. This helps to ensure a smooth and uninterrupted playback experience for the viewer.
Compatibility with hardware: FMP4 is widely supported by hardware devices, including smartphones, tablets, and smart TVs, which makes it a popular choice for delivering media content to a wide range of devices.
Smaller file sizes: FMP4 supports fragmented delivery, which allows media content to be delivered in smaller file sizes, reducing the amount of bandwidth required to deliver the content and making it easier to stream over the internet.
Fast seeking: FMP4 supports fast seeking, which allows viewers to quickly navigate to specific points in the video without experiencing long buffering times or delays.
Reduced buffering: FMP4's support for fragmented delivery, adaptive streaming, and low-latency streaming can help to reduce buffering and improve the overall viewing experience.
Server-side ad insertion: FMP4 supports server-side ad insertion, which allows for more efficient ad delivery and reduces the risk of ad blockers.
High-quality audio: FMP4 supports high-quality audio, including 5.1 and 7.1 surround sound, which enhances the viewer's audio experience.
Wide range of applications: FMP4 can be used for a wide range of applications, including live streaming, video on demand, and interactive video experiences.
Low cost: FMP4 is a relatively low-cost solution for delivering media content over the internet, which makes it an attractive option for businesses and organizations of all sizes.
Easy to use: FMP4 is easy to use and implement, which reduces the amount of time and resources required to get media content up and running on the internet.
Standards-based: FMP4 is based on open standards, which ensures compatibility with a wide range of devices and platforms.
Integration with content management systems: FMP4 can be easily integrated with content management systems, which allows content owners to easily manage and distribute their media content.
In-band event signaling: FMP4 supports in-band event signaling, which enables the delivery of interactive content and allows content owners to collect data on viewer engagement.
Live transcoding: FMP4 supports live transcoding, which allows media content to be encoded in real-time, reducing the need for pre-encoded content and enabling faster delivery of live streams.
Integration with content delivery networks: FMP4 can be easily integrated with content delivery networks, which ensures fast and reliable delivery of media content to viewers worldwide.
Wide range of codecs: FMP4 supports a wide range of codecs, including H.264, HEVC, and VP9, which allows content owners to deliver media content in the highest quality possible.
Wide range of streaming protocols: FMP4 supports a wide range of streaming protocols, including HTTP Live Streaming (HLS), Dynamic Adaptive Streaming over HTTP (DASH), and Smooth Streaming, which ensures compatibility with a wide range of devices and platforms.
Interoperability: FMP4 is designed for interoperability, which means that media content encoded in FMP4 format can be played back on a wide range of devices and platforms without any compatibility issues.
Subtitles and closed captioning: FMP4 supports the inclusion of subtitles and closed captioning in media content, which enhances the accessibility of the content for viewers with hearing impairments or who speak different languages.
Digital Rights Management (DRM): FMP4 supports various DRM technologies, which allows content owners to protect their content from unauthorized distribution and piracy.
Dynamic packaging: FMP4 supports dynamic packaging, which allows media content to be dynamically packaged in real-time, based on the viewer's device and available bandwidth, ensuring the highest quality viewing experience possible.
Ad insertion at specific times: FMP4 supports ad insertion at specific times in the video, which enables content owners to monetize their content more effectively.
User engagement tracking: FMP4 supports user engagement tracking, which allows content owners to collect data on viewer behavior and preferences, enabling them to optimize their content and improve engagement.
Integration with analytics platforms: FMP4 can be easily integrated with analytics platforms, which allows content owners to track viewer engagement and measure the effectiveness of their content.
Reduced storage costs: FMP4's support for fragmented delivery and dynamic packaging can help to reduce storage costs for media content, as only the necessary segments are stored on the server.
