java.lang.Object javax.sound.sampled.AudioFormat
AudioFormat is the class that specifies a particular arrangement of data in a sound stream. By examing the information stored in the audio format, you can discover how to interpret the bits in the binary sound data.
Every data line has an audio format associated with its data stream. The audio format of a source (playback) data line indicates what kind of data the data line expects to receive for output. For a target (capture) data line, the audio format specifies the kind of the data that can be read from the line. Sound files also have audio formats, of course. The AudioFileFormat class encapsulates an AudioFormat in addition to other, file-specific information. Similarly, an AudioInputStream has an AudioFormat.
The AudioFormat class accommodates a number of common sound-file encoding techniques, including pulse-code modulation (PCM), mu-law encoding, and a-law encoding. These encoding techniques are predefined, but service providers can create new encoding types. The encoding that a specific format uses is named by its encoding field.
In addition to the encoding, the audio format includes other properties that further specify the exact arrangement of the data. These include the number of channels, sample rate, sample size, byte order, frame rate, and frame size. Sounds may have different numbers of audio channels: one for mono, two for stereo. The sample rate measures how many "snapshots" (samples) of the sound pressure are taken per second, per channel. (If the sound is stereo rather than mono, two samples are actually measured at each instant of time: one for the left channel, and another for the right channel; however, the sample rate still measures the number per channel, so the rate is the same regardless of the number of channels. This is the standard use of the term.) The sample size indicates how many bits are used to store each snapshot; 8 and 16 are typical values. For 16-bit samples (or any other sample size larger than a byte), byte order is important; the bytes in each sample are arranged in either the "little-endian" or "big-endian" style. For encodings like PCM, a frame consists of the set of samples for all channels at a given point in time, and so the size of a frame (in bytes) is always equal to the size of a sample (in bytes) times the number of channels. However, with some other sorts of encodings a frame can contain a bundle of compressed data for a whole series of samples, as well as additional, non-sample data. For such encodings, the sample rate and sample size refer to the data after it is decoded into PCM, and so they are completely different from the frame rate and frame size.
An AudioFormat object can include a set of properties. A property is a pair of key and value: the key is of type String, the associated property value is an arbitrary object. Properties specify additional format specifications, like the bit rate for compressed formats. Properties are mainly used as a means to transport additional information of the audio format to and from the service providers. Therefore, properties are ignored in the matches(AudioFormat) method. However, methods which rely on the installed service providers, like (AudioFormat, AudioFormat) isConversionSupported may consider properties, depending on the respective service provider implementation.
The following table lists some common properties which service providers should use, if applicable:
Property key | Value type | Description |
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"bitrate" | Integer | average bit rate in kilobits per second |
"vbr" | Boolean | true, if the file is encoded in variable bit rate (VBR) |
"quality" | Integer | encoding/conversion quality, 1..10 |
Vendors of service providers (plugins) are encouraged to seek information about other already established properties in third party plugins, and follow the same conventions.
Nested Class Summary | |
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static class |
AudioFormat.Encoding
The Encoding class names the specific type of data representation used for an audio stream. |
Field Summary | |
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protected boolean |
bigEndian
Indicates whether the audio data is stored in big-endian or little-endian order. |
protected int |
channels
The number of audio channels in this format (1 for mono, 2 for stereo). |
protected AudioFormat.Encoding |
encoding
The audio encoding technique used by this format. |
protected float |
frameRate
The number of frames played or recorded per second, for sounds that have this format. |
protected int |
frameSize
The number of bytes in each frame of a sound that has this format. |
protected float |
sampleRate
The number of samples played or recorded per second, for sounds that have this format. |
protected int |
sampleSizeInBits
The number of bits in each sample of a sound that has this format. |
Constructor Summary | |
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AudioFormat
(
AudioFormat.Encoding
encoding, float sampleRate, int sampleSizeInBits, int channels, int frameSize, float frameRate, boolean bigEndian) Constructs an AudioFormat with the given parameters. |
|
AudioFormat
(
AudioFormat.Encoding
encoding, float sampleRate, int sampleSizeInBits, int channels, int frameSize, float frameRate, boolean bigEndian,
Map
<
String
,
Object
Constructs an AudioFormat with the given parameters. |
|
AudioFormat
(float sampleRate, int sampleSizeInBits, int channels, boolean signed, boolean bigEndian) Constructs an AudioFormat with a linear PCM encoding and the given parameters. |
Method Summary | |
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int |
getChannels
() Obtains the number of channels. |
AudioFormat.Encoding |
getEncoding
() Obtains the type of encoding for sounds in this format. |
float |
getFrameRate
() Obtains the frame rate in frames per second. |
int |
getFrameSize
() Obtains the frame size in bytes. |
Object |
getProperty
(
String
Obtain the property value specified by the key. |
float |
getSampleRate
() Obtains the sample rate. |
int |
getSampleSizeInBits
() Obtains the size of a sample. |
boolean |
isBigEndian
() Indicates whether the audio data is stored in big-endian or little-endian byte order. |
boolean |
matches
(
AudioFormat
format) Indicates whether this format matches the one specified. |
Map < String , Object |
properties
()
Obtain an unmodifiable map of properties. |
|
|
String |
toString
()
Returns a string that describes the format, such as: "PCM SIGNED 22050 Hz 16 bit mono big-endian". |
Methods inherited from class java.lang. Object |
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clone , equals , finalize , getClass , hashCode , notify , notifyAll , wait , wait , wait |
Field Detail |
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protected AudioFormat.Encoding encoding
protected float sampleRate
protected int sampleSizeInBits
protected int channels
protected int frameSize
protected float frameRate
protected boolean bigEndian
Constructor Detail |
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public AudioFormat(AudioFormat.Encoding encoding, float sampleRate, int sampleSizeInBits, int channels, int frameSize, float frameRate, boolean bigEndian)
public AudioFormat ( AudioFormat.Encoding encoding, float sampleRate, int sampleSizeInBits, int channels, int frameSize, float frameRate, boolean bigEndian, Map< String, Object> properties)
public AudioFormat(float sampleRate, int sampleSizeInBits, int channels, boolean signed, boolean bigEndian)
Method Detail |
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public AudioFormat.Encoding getEncoding()
public float getSampleRate()
public int getSampleSizeInBits()
public int getChannels()
public int getFrameSize()
public float getFrameRate()
public boolean isBigEndian()
public Map< String, Object> properties ()
public ObjectgetProperty ( String key)
If the specified property is not defined for a particular file format, this method returns null.
public boolean matches(AudioFormat format)
public String toString()