jdk/src/java.desktop/share/classes/javax/sound/sampled/Mixer.java

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package javax.sound.sampled;

/**
 * A mixer is an audio device with one or more lines. It need not be designed
 * for mixing audio signals. A mixer that actually mixes audio has multiple
 * input (source) lines and at least one output (target) line. The former are
 * often instances of classes that implement {@link SourceDataLine}, and the
 * latter, {@link TargetDataLine}. {@link Port} objects, too, are either source
 * lines or target lines. A mixer can accept prerecorded, loopable sound as
 * input, by having some of its source lines be instances of objects that
 * implement the {@link Clip} interface.
 * <p>
 * Through methods of the {@code Line} interface, which {@code Mixer} extends, a
 * mixer might provide a set of controls that are global to the mixer. For
 * example, the mixer can have a master gain control. These global controls are
 * distinct from the controls belonging to each of the mixer's individual lines.
 * <p>
 * Some mixers, especially those with internal digital mixing capabilities, may
 * provide additional capabilities by implementing the {@code DataLine}
 * interface.
 * <p>
 * A mixer can support synchronization of its lines. When one line in a
 * synchronized group is started or stopped, the other lines in the group
 * automatically start or stop simultaneously with the explicitly affected one.
 *
 * @author Kara Kytle
 * @since 1.3
 */
public interface Mixer extends Line {

    /**
     * Obtains information about this mixer, including the product's name,
     * version, vendor, etc.
     *
     * @return a mixer info object that describes this mixer
     * @see Info
     */
    Info getMixerInfo();

    /**
     * Obtains information about the set of source lines supported by this
     * mixer. Some source lines may only be available when this mixer is open.
     *
     * @return array of {@code Line.Info} objects representing source lines for
     *         this mixer. If no source lines are supported, an array of length
     *         0 is returned.
     */
    Line.Info[] getSourceLineInfo();

    /**
     * Obtains information about the set of target lines supported by this
     * mixer. Some target lines may only be available when this mixer is open.
     *
     * @return array of {@code Line.Info} objects representing target lines for
     *         this mixer. If no target lines are supported, an array of length
     *         0 is returned.
     */
    Line.Info[] getTargetLineInfo();

    /**
     * Obtains information about source lines of a particular type supported by
     * the mixer. Some source lines may only be available when this mixer is
     * open.
     *
     * @param  info a {@code Line.Info} object describing lines about which
     *         information is queried
     * @return an array of {@code Line.Info} objects describing source lines
     *         matching the type requested. If no matching source lines are
     *         supported, an array of length 0 is returned.
     */
    Line.Info[] getSourceLineInfo(Line.Info info);

    /**
     * Obtains information about target lines of a particular type supported by
     * the mixer. Some target lines may only be available when this mixer is
     * open.
     *
     * @param  info a {@code Line.Info} object describing lines about which
     *         information is queried
     * @return an array of {@code Line.Info} objects describing target lines
     *         matching the type requested. If no matching target lines are
     *         supported, an array of length 0 is returned.
     */
    Line.Info[] getTargetLineInfo(Line.Info info);

    /**
     * Indicates whether the mixer supports a line (or lines) that match the
     * specified {@code Line.Info} object. Some lines may only be supported when
     * this mixer is open.
     *
     * @param  info describes the line for which support is queried
     * @return {@code true} if at least one matching line is supported,
     *         {@code false} otherwise
     */
    boolean isLineSupported(Line.Info info);

    /**
     * Obtains a line that is available for use and that matches the description
     * in the specified {@code Line.Info} object.
     * <p>
     * If a {@code DataLine} is requested, and {@code info} is an instance of
     * {@code DataLine.Info} specifying at least one fully qualified audio
     * format, the last one will be used as the default format of the returned
     * {@code DataLine}.
     *
     * @param  info describes the desired line
     * @return a line that is available for use and that matches the description
     *         in the specified {@code Line.Info} object
     * @throws LineUnavailableException if a matching line is not available due
     *         to resource restrictions
     * @throws IllegalArgumentException if this mixer does not support any lines
     *         matching the description
     * @throws SecurityException if a matching line is not available due to
     *         security restrictions
     */
    Line getLine(Line.Info info) throws LineUnavailableException;

    //$$fb 2002-04-12: fix for 4667258: behavior of Mixer.getMaxLines(Line.Info) method doesn't match the spec
    /**
     * Obtains the approximate maximum number of lines of the requested type
     * that can be open simultaneously on the mixer.
     * <p>
     * Certain types of mixers do not have a hard bound and may allow opening
     * more lines. Since certain lines are a shared resource, a mixer may not be
     * able to open the maximum number of lines if another process has opened
     * lines of this mixer.
     * <p>
     * The requested type is any line that matches the description in the
     * provided {@code Line.Info} object. For example, if the info object
     * represents a speaker port, and the mixer supports exactly one speaker
     * port, this method should return 1. If the info object represents a source
     * data line and the mixer supports the use of 32 source data lines
     * simultaneously, the return value should be 32. If there is no limit, this
     * function returns {@link AudioSystem#NOT_SPECIFIED}.
     *
     * @param  info a {@code Line.Info} that describes the line for which the
     *         number of supported instances is queried
     * @return the maximum number of matching lines supported, or
     *         {@code AudioSystem.NOT_SPECIFIED}
     */
    int getMaxLines(Line.Info info);

    /**
     * Obtains the set of all source lines currently open to this mixer.
     *
     * @return the source lines currently open to the mixer. If no source lines
     *         are currently open to this mixer, an array of length 0 is
     *         returned.
     * @throws SecurityException if the matching lines are not available due to
     *         security restrictions
     */
    Line[] getSourceLines();

    /**
     * Obtains the set of all target lines currently open from this mixer.
     *
     * @return target lines currently open from the mixer. If no target lines
     *         are currently open from this mixer, an array of length 0 is
     *         returned.
     * @throws SecurityException if the matching lines are not available due to
     *         security restrictions
     */
    Line[] getTargetLines();

    /**
     * Synchronizes two or more lines. Any subsequent command that starts or
     * stops audio playback or capture for one of these lines will exert the
     * same effect on the other lines in the group, so that they start or stop
     * playing or capturing data simultaneously.
     *
     * @param  lines the lines that should be synchronized
     * @param  maintainSync {@code true} if the synchronization must be
     *         precisely maintained (i.e., the synchronization must be
     *         sample-accurate) at all times during operation of the lines, or
     *         {@code false} if precise synchronization is required only during
     *         start and stop operations
     * @throws IllegalArgumentException if the lines cannot be synchronized.
     *         This may occur if the lines are of different types or have
     *         different formats for which this mixer does not support
     *         synchronization, or if all lines specified do not belong to this
     *         mixer.
     */
    void synchronize(Line[] lines, boolean maintainSync);

    /**
     * Releases synchronization for the specified lines. The array must be
     * identical to one for which synchronization has already been established;
     * otherwise an exception may be thrown. However, {@code null} may be
     * specified, in which case all currently synchronized lines that belong to
     * this mixer are unsynchronized.
     *
     * @param  lines the synchronized lines for which synchronization should be
     *         released, or {@code null} for all this mixer's synchronized lines
     * @throws IllegalArgumentException if the lines cannot be unsynchronized.
     *         This may occur if the argument specified does not exactly match a
     *         set of lines for which synchronization has already been
     *         established.
     */
    void unsynchronize(Line[] lines);

    /**
     * Reports whether this mixer supports synchronization of the specified set
     * of lines.
     *
     * @param  lines the set of lines for which synchronization support is
     *         queried
     * @param  maintainSync {@code true} if the synchronization must be
     *         precisely maintained (i.e., the synchronization must be
     *         sample-accurate) at all times during operation of the lines, or
     *         {@code false} if precise synchronization is required only during
     *         start and stop operations
     * @return {@code true} if the lines can be synchronized, {@code false}
     *         otherwise
     */
    boolean isSynchronizationSupported(Line[] lines, boolean maintainSync);

    /**
     * The {@code Mixer.Info} class represents information about an audio mixer,
     * including the product's name, version, and vendor, along with a textual
     * description. This information may be retrieved through the
     * {@link Mixer#getMixerInfo() getMixerInfo} method of the {@code Mixer}
     * interface.
     *
     * @author Kara Kytle
     * @since 1.3
     */
    class Info {

        /**
         * Mixer name.
         */
        private final String name;

        /**
         * Mixer vendor.
         */
        private final String vendor;

        /**
         * Mixer description.
         */
        private final String description;

        /**
         * Mixer version.
         */
        private final String version;

        /**
         * Constructs a mixer's info object, passing it the given textual
         * information.
         *
         * @param  name the name of the mixer
         * @param  vendor the company who manufactures or creates the hardware
         *         or software mixer
         * @param  description descriptive text about the mixer
         * @param  version version information for the mixer
         */
        protected Info(String name, String vendor, String description, String version) {

            this.name = name;
            this.vendor = vendor;
            this.description = description;
            this.version = version;
        }

        /**
         * Indicates whether the specified object is equal to this info object,
         * returning {@code true} if the objects are the same.
         *
         * @param  obj the reference object with which to compare
         * @return {@code true} if the specified object is equal to this info
         *         object; {@code false} otherwise
         */
        @Override
        public final boolean equals(Object obj) {
            return super.equals(obj);
        }

        /**
         * Returns a hash code value for this info object.
         *
         * @return a hash code value for this info object
         */
        @Override
        public final int hashCode() {
            return super.hashCode();
        }

        /**
         * Obtains the name of the mixer.
         *
         * @return a string that names the mixer
         */
        public final String getName() {
            return name;
        }

        /**
         * Obtains the vendor of the mixer.
         *
         * @return a string that names the mixer's vendor
         */
        public final String getVendor() {
            return vendor;
        }

        /**
         * Obtains the description of the mixer.
         *
         * @return a textual description of the mixer
         */
        public final String getDescription() {
            return description;
        }

        /**
         * Obtains the version of the mixer.
         *
         * @return textual version information for the mixer
         */
        public final String getVersion() {
            return version;
        }

        /**
         * Returns a string representation of the info object.
         *
         * @return a string representation of the info object
         */
        @Override
        public final String toString() {
            return String.format("%s, version %s", name, version);
        }
    }
}