Android支持的音频格式

本文主要是介绍Android支持的音频格式，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

转载自：http://my.oschina.net/AlexZhuang/blog/56207 以及http://developer.android.com/guide/topics/media/mediaplayer.html

AAC: Advanced Audio Coding codec (as well as both profiles of HE-AAC, High Efficiency AAC), .m4a (audio/m4a) or.3gp (audio/3gpp) files. AAC is a popular standard that is used by the iPod and other portable media players. Android supports this audio format inside of MPEG-4 audio files and inside of 3GP files (which are based on the MPEG-4

format). Recent additions to the AAC specification, High Efficiency AAC are also supported.

AAC（Advanced Audio Coding），中文称为“高级音频编码”，出现于1997年，基于 MPEG-2的音频编码技术。

优点：相对于mp3，AAC格式的音质更佳，文件更小。

不足：AAC属于有损压缩的格式，与时下流行的APE、FLAC等无损格式相比音质存在“本质上”的差距。加之，目前传输速度更快的USB3.0和16G以上大容量MP3正在加速普及，也使得AAC头上“小巧”的光环不复存在了。

前景：以发展的眼光来看，正如“高清”正在被越来越多的人所接受一样，“无损”必定是未来音乐格式的绝对主流。AAC这种“有损”格式的前景不容乐观。

MP3: MPEG-1 Audio Layer 3, .mp3 (audio/mp3) files. MP3, probably the most widely used audio codec, is supported. This allows Android to utilize the vast majority of audio available online through various web sites and music stores.

MP3是一种音频压缩技术，其全称是动态影像专家压缩标准音频层面3（Moving Picture Experts Group Audio Layer III），简称为MP3。它被设计用来大幅度地降低音频数据量。利用 MPEG Audio Layer 3 的技术，将音乐以1:10 甚至 1:12 的压缩率，压缩成容量较小的文件，而对于大多数用户来说重放的音质与最初的不压缩音频相比没有明显的下降。

根据MPEG规范的说法，MPEG-4中的AAC（Advanced audio coding）将是MP3格式的下一代。MP3还分为耳机MP3和外放MP3两大类，传统MP3需要带耳机才有很好的音质，但是对人们的耳膜有所伤害，新型的MP3主要方向是外放MP3，对耳膜几乎没有任何伤害，从而得到人们的喜爱。

AMR: Adaptive Multi-Rate codec (both AMR Narrowband, AMR-NB, and AMR Wideband, AMR-WB), .3gp (audio/3gpp) or .amr (audio/amr) files. AMR is the audio codec that has been standardized as the primary voice audio codec in use by the 3GPP (3rd Generation Partnership Project). The 3GPP is a telecommunications industry organization that creates specifications for the partner companies to use. In other words, the AMR codec is what is primarily used for voice

calling applications on modern mobile phones and generally supported across mobile handset manufacturers and carriers. As such, this codec is generally useful for voice encoding but doesn’t perform well for more complex types of audio such as music.

全称Adaptive Multi-Rate和Adaptive Multi-Rate Wideband，主要用于移动设备的音频，压缩比比较大，但相对其他的压缩格式质量比较差，由于多用于人声，通话，效果还是很不错的。

Ogg : Ogg Vorbis, .ogg (application/ogg) files. Ogg Vorbis is an open source, patent-free audio codec with quality that is comparable to commercial and patent-encumbered codecs such as MP3 and AAC. It was developed by volunteers and is currently maintained by the Xiph.Org foundation.

Ogg全称应该是OGGVobis(oggVorbis)是一种新的音频压缩格式，类似于MP3等的音乐格式。Ogg是完全免费、开放和没有专利限制的。OggVorbis文件的扩展名是.OGG。Ogg 文件格式可以不断地进行大小和音质的改良，而不影响旧有的编码器或播放器。

PCM: Pulse Code Modulation commonly used in WAVE or WAV files (Waveform Audio Format), .wav (audio/x-wav) files. PCM is the technique used for storing audio on computers and other digital audio devices. It is generally an uncompressed audio file with data that represents the amplitude of a piece of audio over time. The “sample rate” is how often an amplitude reading is stored. The “bit-depth” is how many bits are used to represent an individual sample. A piece of audio data with a sample rate of 16kHz and a bit-depth of 32 bits means that it will contain 32 bits of data representing the amplitude of the audio and it will have 16,000 of these per second. The higher the sample rate and the higher the bit-depth, the more accurate the digitization of the audio is. Sample rate and bit-depth also determine how large the audio file will be when its length is taken into account. Android supports PCM audio data within WAV files. WAV is a long-standing standard audio format on PCs.

脉冲编码调制（PulseCodeModulation），简称PCM。是数字信号是对连续变化的模拟信号进行抽样、量化和编码产生。PCM的优点就是音质好，缺点就是体积大。PCM可以提供用户从2M到155M速率的数字数据专线业务，也可以提供话音、图象传送、远程教学等其他业务。PCM有两个标准（表现形式）：E1和T1。

Supported Media Formats

IN THIS DOCUMENT

Network Protocols
Core Media Formats
Video Encoding Recommendations

KEY CLASSES

MediaPlayer
MediaRecorder

This document describes the media codec, container, and network protocol support provided by the Android platform.

As an application developer, you are free to make use of any media codec that is available on any Android-powered device, including those provided by the Android platform and those that are device-specific. However, it is a best practice to use media encoding profiles that are device-agnostic.

Network Protocols

The following network protocols are supported for audio and video playback:

RTSP (RTP, SDP)
HTTP/HTTPS progressive streaming
HTTP/HTTPS live streaming draft protocol:
- MPEG-2 TS media files only
- Protocol version 3 (Android 4.0 and above)
- Protocol version 2 (Android 3.x)
- Not supported before Android 3.0

Note: HTTPS is not supported before Android 3.1.

Core Media Formats

The table below describes the media format support built into the Android platform. Note that any given mobile device may provide support for additional formats or file types not listed in the table.

Note: Media codecs that are not guaranteed to be available on all Android platform versions are accordingly noted in parentheses—for example "(Android 3.0+)".

Table 1. Core media format and codec support.

Type	Format / Codec	Encoder	Decoder	Details	Supported File Type(s) / Container Formats
Audio	AAC LC	•	•	Support for mono/stereo/5.0/5.1 content with standard sampling rates from 8 to 48 kHz.	• 3GPP (.3gp) • MPEG-4 (.mp4, .m4a) • ADTS raw AAC (.aac, decode in Android 3.1+, encode in Android 4.0+, ADIF not supported) • MPEG-TS (.ts, not seekable, Android 3.0+)
	HE-AACv1 (AAC+)	• (Android 4.1+)	•
	HE-AACv2 (enhanced AAC+)		•	Support for stereo/5.0/5.1 content with standard sampling rates from 8 to 48 kHz.
	AAC ELD (enhanced low delay AAC)	• (Android 4.1+)	• (Android 4.1+)	Support for mono/stereo content with standard sampling rates from 16 to 48 kHz
	AMR-NB	•	•	4.75 to 12.2 kbps sampled @ 8kHz	3GPP (.3gp)
	AMR-WB	•	•	9 rates from 6.60 kbit/s to 23.85 kbit/s sampled @ 16kHz	3GPP (.3gp)
	FLAC		• (Android 3.1+)	Mono/Stereo (no multichannel). Sample rates up to 48 kHz (but up to 44.1 kHz is recommended on devices with 44.1 kHz output, as the 48 to 44.1 kHz downsampler does not include a low-pass filter). 16-bit recommended; no dither applied for 24-bit.	FLAC (.flac) only
	MP3		•	Mono/Stereo 8-320Kbps constant (CBR) or variable bit-rate (VBR)	MP3 (.mp3)
	MIDI		•	MIDI Type 0 and 1. DLS Version 1 and 2. XMF and Mobile XMF. Support for ringtone formats RTTTL/RTX, OTA, and iMelody	• Type 0 and 1 (.mid, .xmf, .mxmf) • RTTTL/RTX (.rtttl, .rtx) • OTA (.ota) • iMelody (.imy)
	Vorbis		•		• Ogg (.ogg) • Matroska (.mkv, Android 4.0+)
	PCM/WAVE	• (Android 4.1+)	•	8- and 16-bit linear PCM (rates up to limit of hardware). Sampling rates for raw PCM recordings at 8000, 16000 and 44100 Hz.	WAVE (.wav)
Image	JPEG	•	•	Base+progressive	JPEG (.jpg)
	GIF		•		GIF (.gif)
	PNG	•	•		PNG (.png)
	BMP		•		BMP (.bmp)
	WebP	• (Android 4.0+) (Lossless, Transparency, Android 4.2.1+)	• (Android 4.0+) (Lossless, Transparency, Android 4.2.1+)		WebP (.webp)
Video	H.263	•	•		• 3GPP (.3gp) • MPEG-4 (.mp4)
	H.264 AVC	• (Android 3.0+)	•	Baseline Profile (BP)	• 3GPP (.3gp) • MPEG-4 (.mp4) • MPEG-TS (.ts, AAC audio only, not seekable, Android 3.0+)
	MPEG-4 SP		•		3GPP (.3gp)
	VP8	• (Android 4.3+)	• (Android 2.3.3+)	Streamable only in Android 4.0 and above	• WebM (.webm) • Matroska (.mkv, Android 4.0+)

Video Encoding Recommendations

Table 2, below, lists examples of video encoding profiles and parameters that the Android media framework supports for playback in the H.264 Baseline Profile codec. While table 3 lists examples that the framework supports for playback in the VP8 media codec.

In addition to these encoding parameter recommendations, a device's available video recording profiles can be used as a proxy for media playback capabilities. These profiles can be inspected using the CamcorderProfileclass, which is available since API level 8.

Table 2. Examples of supported video encoding parameters for the H.264 Baseline Profile codec.

	SD (Low quality)	SD (High quality)	HD 720p (N/A on all devices)
Video resolution	176 x 144 px	480 x 360 px	1280 x 720 px
Video frame rate	12 fps	30 fps	30 fps
Video bitrate	56 Kbps	500 Kbps	2 Mbps
Audio codec	AAC-LC	AAC-LC	AAC-LC
Audio channels	1 (mono)	2 (stereo)	2 (stereo)
Audio bitrate	24 Kbps	128 Kbps	192 Kbps

Table 3. Examples of supported video encoding parameters for the VP8 codec.

	SD (Low quality)	SD (High quality)	HD 720p (N/A on all devices)	HD 1080p (N/A on all devices)
Video resolution	320 x 180 px	640 x 360 px	1280 x 720 px	1920 x 1080 px
Video frame rate	30 fps	30 fps	30 fps	30 fps
Video bitrate	800 Kbps	2 Mbps	4 Mbps	10 Mbps

For video content that is streamed over HTTP or RTSP, there are additional requirements:

For 3GPP and MPEG-4 containers, the moov atom must precede any mdat atoms, but must succeed the ftypatom.
For 3GPP, MPEG-4, and WebM containers, audio and video samples corresponding to the same time offset may be no more than 500 KB apart. To minimize this audio/video drift, consider interleaving audio and video in smaller chunk sizes.

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