javax.sound.sampled.AudioFormat — clojure-interop/javax.sound 1.0.5

AudioFormat is the class that specifies a particular arrangement of data in a sound stream. By examining 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:

Audio Format Properties

Property key Value type Description

"bitrate" Integer average bit rate in bits per second

"vbr" Boolean true, if the file is encoded in variable bit rate (VBR)

"quality" Integer encoding/conversion quality, 1..100

Vendors of service providers (plugins) are encouraged to seek information about other already established properties in third party plugins, and follow the same conventions.

->audio-format clj

(->audio-format sample-rate sample-size-in-bits channels signed big-endian)

(->audio-format encoding
                sample-rate
                sample-size-in-bits
                channels
                frame-size
                frame-rate
                big-endian)

(->audio-format encoding
                sample-rate
                sample-size-in-bits
                channels
                frame-size
                frame-rate
                big-endian
                properties)

Constructor.

Constructs an AudioFormat with the given parameters. The encoding specifies the convention used to represent the data. The other parameters are further explained in the class description.

encoding - the audio encoding technique - javax.sound.sampled.AudioFormat$Encoding sample-rate - the number of samples per second - float sample-size-in-bits - the number of bits in each sample - int channels - the number of channels (1 for mono, 2 for stereo, and so on) - int frame-size - the number of bytes in each frame - int frame-rate - the number of frames per second - float big-endian - indicates whether the data for a single sample is stored in big-endian byte order (false means little-endian) - boolean properties - a Map<String,Object> object containing format properties - java.util.Map

big-endian? clj

(big-endian? this)

Indicates whether the audio data is stored in big-endian or little-endian byte order. If the sample size is not more than one byte, the return value is irrelevant.

returns: true if the data is stored in big-endian byte order, false if little-endian - boolean

get-channels clj

(get-channels this)

Obtains the number of channels. When this AudioFormat is used for queries (e.g. AudioSystem.isConversionSupported) or capabilities (e.g. DataLine.Info.getFormats), a return value of AudioSystem.NOT_SPECIFIED means that any (positive) number of channels is acceptable.

returns: The number of channels (1 for mono, 2 for stereo, etc.), or AudioSystem.NOT_SPECIFIED - int

get-encoding clj

(get-encoding this)

Obtains the type of encoding for sounds in this format.

returns: the encoding type - javax.sound.sampled.AudioFormat$Encoding

get-frame-rate clj

(get-frame-rate this)

Obtains the frame rate in frames per second. When this AudioFormat is used for queries (e.g. AudioSystem.isConversionSupported) or capabilities (e.g. DataLine.Info.getFormats), a frame rate of AudioSystem.NOT_SPECIFIED means that any frame rate is acceptable. AudioSystem.NOT_SPECIFIED is also returned when the frame rate is not defined for this audio format.

returns: the number of frames per second, or AudioSystem.NOT_SPECIFIED - float

get-frame-size clj

(get-frame-size this)

Obtains the frame size in bytes. When this AudioFormat is used for queries (e.g. AudioSystem.isConversionSupported) or capabilities (e.g. DataLine.Info.getFormats), a frame size of AudioSystem.NOT_SPECIFIED means that any frame size is acceptable. AudioSystem.NOT_SPECIFIED is also returned when the frame size is not defined for this audio format.

returns: the number of bytes per frame, or AudioSystem.NOT_SPECIFIED - int

get-property clj

(get-property this key)

Obtain the property value specified by the key. The concept of properties is further explained in the class description.

If the specified property is not defined for a particular file format, this method returns null.

key - the key of the desired property - java.lang.String

returns: the value of the property with the specified key, or null if the property does not exist. - java.lang.Object

get-sample-rate clj

(get-sample-rate this)

Obtains the sample rate. For compressed formats, the return value is the sample rate of the uncompressed audio data. When this AudioFormat is used for queries (e.g. AudioSystem.isConversionSupported) or capabilities (e.g. DataLine.Info.getFormats), a sample rate of AudioSystem.NOT_SPECIFIED means that any sample rate is acceptable. AudioSystem.NOT_SPECIFIED is also returned when the sample rate is not defined for this audio format.

returns: the number of samples per second, or AudioSystem.NOT_SPECIFIED - float

get-sample-size-in-bits clj

(get-sample-size-in-bits this)

Obtains the size of a sample. For compressed formats, the return value is the sample size of the uncompressed audio data. When this AudioFormat is used for queries (e.g. AudioSystem.isConversionSupported) or capabilities (e.g. DataLine.Info.getFormats), a sample size of AudioSystem.NOT_SPECIFIED means that any sample size is acceptable. AudioSystem.NOT_SPECIFIED is also returned when the sample size is not defined for this audio format.

returns: the number of bits in each sample, or AudioSystem.NOT_SPECIFIED - int

matches clj

(matches this format)

Indicates whether this format matches the one specified. To match, two formats must have the same encoding, and consistent values of the number of channels, sample rate, sample size, frame rate, and frame size. The values of the property are consistent if they are equal or the specified format has the property value AudioSystem.NOT_SPECIFIED. The byte order (big-endian or little-endian) must be the same if the sample size is greater than one byte.

format - format to test for match - javax.sound.sampled.AudioFormat

returns: true if this format matches the one specified, false otherwise. - boolean

properties clj

(properties this)

Obtain an unmodifiable map of properties. The concept of properties is further explained in the class description.

returns: a Map<String,Object> object containing all properties. If no properties are recognized, an empty map is returned. - java.util.Map<java.lang.String,java.lang.Object>

to-string clj

(to-string this)

Returns a string that describes the format, such as: "PCM SIGNED 22050 Hz 16 bit mono big-endian". The contents of the string may vary between implementations of Java Sound.

returns: a string that describes the format parameters - java.lang.String