音頻 & 視頻的起始點

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iOS中的多媒體技術(shù)使你具備訪問iPhone、iPad和iPod touch中的復(fù)雜音頻和視頻的能力。專業(yè)的類能讓你輕松的添加諸如 iPod library playback 以及 視頻捕獲等基本的功能，而豐富的多媒體API能夠提供高級的解決方案。

選擇你所需要的技術(shù)：

想要從iPod庫或本地播放音頻文件，或播放視頻流，要使用 Media Player framework。在這個框架中得類自動支持發(fā)送音頻或視頻到AirPlay的設(shè)備，例如Apple TV。

想要輕松的添加圖片或者視頻到你的軟件，需使用UIKit framework中得專用類和函數(shù)。

想要使用基本的音頻錄制和回放，包括立體聲、同步和計量，需使用 AV Foundation framework 中的一些音頻類。

想要添加高性能位置音頻回放你的OpenGL-based游戲或其他應(yīng)用程序，需使用開源OpenAL(打開音頻庫)的API。

想要使用諸如VoIP、流媒體、虛擬樂器、或MIDI（Musical Instrument Digital Interface，樂器數(shù)字接口）等高性能音頻視頻數(shù)據(jù)或先進方案，需使用AV Foundation framework、 the Assets（資產(chǎn)） Library framework、 各種音頻核心框架(包括 Core Audio、Audio Toolbox、 和 AudioFrameworksEworks)、 和 Core MIDI framework。

內(nèi)容:

Get Up and Running

Become Proficient in Audio Development

Become Proficient in Video Development

Get Up and Running

起點與運行

通過下面的這些資源，熟悉iOS的音頻開發(fā)：

讀 Multimedia Programming Guide 中的 “Using Audio”，學習關(guān)于iOS設(shè)備的音頻開發(fā)。一定要理解 Multimedia Programming Guide 中的 “The Basics: Audio Codecs, Supported Audio Formats, and Audio Sessions” 中介紹的關(guān)于音頻會話對象的重要性。

View the avTouch sample code project, which shows how to play sounds with the AVAudioPlayer class; the SpeakHere project, which demonstrates basic recording and playback; and the Audio UI Sounds (SysSound) project, which demonstrates how to invoke vibration and play alerts and user-interface sound effects.

查看avTouch示例代碼項目，它展示了如何用AVAudioPlayer類播放聲音；在SpeakHere 工程，它示范了基本的錄音和回放；在Audio UI Sounds (SysSound) 工程，它示范了如何調(diào)用震動和播放警報以及用戶界面音效。

Download and explore the AddMusic sample code project to see a simple demonstration of how to add iPod library playback to your app.

下載并探索AddMusic 示例代碼工程，來看一個簡單的演示如何添加iPod庫的播放到你的app。

Read MPVolumeView Class Reference to learn how to quickly add AirPlay capability to your app.

閱讀MPVolumeView Class Reference來學習如何快速的添加AirPlay 功能到你的app。

Get up and running with iOS video development with these resources:

通過下面資源，熟悉iOS 視頻開發(fā)：

Read “Using Video” in Multimedia Programming Guide for an overview of video recording and playback on iOS devices.

閱讀Multimedia Programming Guide 中的“Using Video” 來看在iOS設(shè)備上進行視頻錄制和回放的概述。

View the MoviePlayer sample code project, which demonstrates the powerful MPMoviePlayerController class for playing local or streamed video content; and the Using UIImagePickerController to Select Pictures and Take Photos project, which demonstrates simple movie and picture capture using the UIKit framework.

查看MoviePlayer 示例代碼工程，它示范了強大的MPMoviePlayerController 類來播放本地的以及流視頻內(nèi)容；以及Using UIImagePickerController to Select Pictures and Take Photos 工程，它示范了使用UIKit 框架進行簡單的視頻和圖像捕捉。

Continue by reading Camera Programming Topics for iOS to learn how take pictures and movies, and to browse the photo library, using the UIImagePickerController class.

閱讀 Camera Programming Topics for iOS來繼續(xù)學習如何制作照片和視頻，并使用UIImagePickerController 類來瀏覽照片庫。

Become Proficient in Audio Development

精通音頻開發(fā)

Gain a complete understanding of audio session objects, and how they determine your app’s audio behavior, by reading Audio Session Programming Guide. Also be sure to read “Sound” in iOS Human Interface Guidelines, which explains how your app should handle sound to meet user expectations.

通過閱讀Audio Session Programming Guide獲得一個對音頻隊列對象的完整理解，并且理解他們?nèi)绾未_定app的音頻行為。也要讀iOS Human Interface Guidelines中的“Sound”，它解釋了app應(yīng)該如何處理聲音來滿足用戶的期望。

No matter which iOS audio technologies you employ, users expect to be able to play and pause your app’s audio using the system transport controls in the multitasking UI. To learn how to support this feature, read “Remote Control of Multimedia” in Event Handling Guide for iOS.

無論你使用哪個iOS 音頻技術(shù)，用戶希望使用系統(tǒng)傳輸控制的多任務(wù)UI來播放以及暫停app的音頻。想要學習這個功能的支持，閱讀Event Handling Guide for iOS中的“Remote Control of Multimedia”。

Take full advantage of the iPod library by reading iPod Library Access Programming Guide along with Media Player Framework Reference.

通過閱讀 iPod Library Access Programming Guide 以及 Media Player Framework Reference.來充分理解iPod庫

To learn how to play audio using OpenAL, view the oalTouch project. The website openal.org hosts documentation for the open-source OpenAL API.

想要學習如何使用OpenAL來播放音頻，參看oalTouch 工程。網(wǎng)站openal.org有開源的OpenAL API。

To play streamed audio content, such as from a network connection, use an AVPlayer object as described in “Playback” in AV Foundation Programming Guide. You can also play certain Internet audio files by using the MPMoviePlayerController class; for sample code that shows how, see MoviePlayer.

想要播放音頻流內(nèi)容，例如從網(wǎng)絡(luò)連接得到的，使用一個如AV Foundation Programming Guide中的“Playback”所描述的AVPlayer 對象。你也可以通過使用MPMoviePlayerController 類來播放某些互聯(lián)網(wǎng)音頻文件；示例代碼可以參看MoviePlayer。

To play audio files with stereo panning, synchronization, and metering, use the AVAudioPlayer class. To record audio, use the AVAudioRecorder class. Apple recommends these classes for audio playback and recording when you do not need direct access to audio data.

想要在播放音頻文件的時候有stereo panning，synchronization以及metering，使用AVAudioPlayer 類。想要錄制音頻，使用AVAudioRecorder 類。當你不需要直接訪問音頻數(shù)據(jù)的時候，Apple 建議使用這些為音頻回放和錄制的類。

To get started with handling audio data directly, read Core Audio Essentials in Core Audio Overview to learn about the architecture, programming conventions, and use of Core Audio.

想要開始直接處理音頻數(shù)據(jù)，閱讀Core Audio Overview中的Core Audio Essentials來學習關(guān)于體系架構(gòu)、編程約定以及使用Core Audio的內(nèi)容。

If you are creating a VoIP (voice over Internet protocol) app or a virtual music instrument, you need the highest audio performance available in iOS. The solution to use is audio units, the iOS audio plug-in technology. Audio units also provide advanced capabilities including mixing and equalization. Read Audio Unit Hosting Guide for iOS to learn how to use audio units. View the Audio Mixer (MixerHost) and iPhoneMixerEQGraphTest sample code projects.

如果你創(chuàng)建了一個VoIP（互聯(lián)網(wǎng)語音傳輸協(xié)議）app或者虛擬樂器，你需要在iOS中最高的可能的音頻效果。解決的方案是使用音頻單元，iOS音頻插件基礎(chǔ)。音頻單元還提供高級的功能包括混音和均衡。閱讀Audio Unit Hosting Guide for iOS 來學習如何使用音頻單元。查看Audio Mixer (MixerHost) 和iPhoneMixerEQGraphTest的示例代碼工程。

To create a MIDI app for connecting hardware keyboards or synthesizers to an iOS device, refer to Core MIDI Framework Reference and look at the MFi program.

想要創(chuàng)建一個MIDI app來連接硬件鍵盤或合成器到iOS設(shè)備，參考Core MIDI Framework Reference 以及看看MFi program。

Become Proficient in Video Development

精通視頻開發(fā)

To progress beyond the capabilities of the Media Player framework and the UIImagePickerController class, read AV Foundation Programming Guide. AV Foundation, with support from the Assets Library and Core Media frameworks, provides tools for advanced video solutions including track-based editing, transcoding, and direct access to data from the camera and microphone.

想要超越Media Player 框架的功能以及UIImagePickerController 類，閱讀AV Foundation Programming Guide。AV Foundation，支持Assets Library 和Core Media框架，為提高視頻解決包括track-based 編輯、代碼轉(zhuǎn)換、以及直接訪問來自相機或麥克風的數(shù)據(jù)提供工具。

View the AVCam for iOS sample code project to see how to capture still p_w_picpaths and movies using the AV Foundation framework. AVCam demonstrates the use of several important AV Foundation classes. View the AVPlayerDemo project to see how to play movies from the iPod library.

參閱AVCam for iOS 示例代碼工程來看看如何使用AV Foundation 框架得到靜止的畫面以及視頻。AVCam演示使用了幾種重要的AV Foundation 類。參閱AVPlayerDemo 工程來看如何播放來自iPod庫的視頻。