RTP: update javadocs.

package android.net.rtp;

import android.media.AudioManager;

import java.util.HashMap;

import java.util.Map;

/**

 * An AudioGroup acts as a router connected to the speaker, the microphone, and

 * {@link AudioStream}s. Its execution loop consists of four steps. First, for

 * each AudioStream not in {@link RtpStream#MODE_SEND_ONLY}, decodes its

 * incoming packets and stores in its buffer. Then, if the microphone is

 * enabled, processes the recorded audio and stores in its buffer. Third, if the

 * speaker is enabled, mixes and playbacks buffers of all AudioStreams. Finally,

 * for each AudioStream not in {@link RtpStream#MODE_RECEIVE_ONLY}, mixes all

 * other buffers and sends back the encoded packets. An AudioGroup does nothing

 * if there is no AudioStream in it.

 * An AudioGroup is an audio hub for the speaker, the microphone, and

 * {@link AudioStream}s. Each of these components can be logically turned on

 * or off by calling {@link #setMode(int)} or {@link RtpStream#setMode(int)}.

 * The AudioGroup will go through these components and process them one by one

 * within its execution loop. The loop consists of four steps. First, for each

 * AudioStream not in {@link RtpStream#MODE_SEND_ONLY}, decodes its incoming

 * packets and stores in its buffer. Then, if the microphone is enabled,

 * processes the recorded audio and stores in its buffer. Third, if the speaker

 * is enabled, mixes all AudioStream buffers and plays back. Finally, for each

 * AudioStream not in {@link RtpStream#MODE_RECEIVE_ONLY}, mixes all other

 * buffers and sends back the encoded packets. An AudioGroup does nothing if

 * there is no AudioStream in it.

 *

 * <p>Few things must be noticed before using these classes. The performance is

 * highly related to the system load and the network bandwidth. Usually a

 * simpler {@link AudioCodec} costs fewer CPU cycles but requires more network

 * bandwidth, and vise versa. Using two AudioStreams at the same time not only

 * doubles the load but also the bandwidth. The condition varies from one device

 * to another, and developers must choose the right combination in order to get

 * the best result.

 * bandwidth, and vise versa. Using two AudioStreams at the same time doubles

 * not only the load but also the bandwidth. The condition varies from one

 * device to another, and developers should choose the right combination in

 * order to get the best result.</p>

 *

 * <p>It is sometimes useful to keep multiple AudioGroups at the same time. For

 * example, a Voice over IP (VoIP) application might want to put a conference

 * call on hold in order to make a new call but still allow people in the

 * previous call to talk to each other. This can be done easily using two

 * conference call talking to each other. This can be done easily using two

 * AudioGroups, but there are some limitations. Since the speaker and the

 * microphone are shared globally, only one AudioGroup is allowed to run in

 * modes other than {@link #MODE_ON_HOLD}. In addition, before adding an

 * AudioStream into an AudioGroup, one should always put all other AudioGroups

 * into {@link #MODE_ON_HOLD}. That will make sure the audio driver correctly

 * initialized.</p>

 * microphone are globally shared resources, only one AudioGroup at a time is

 * allowed to run in a mode other than {@link #MODE_ON_HOLD}. The others will

 * be unable to acquire these resources and fail silently.</p>

 *

 * <p class="note">Using this class requires

 * {@link android.Manifest.permission#RECORD_AUDIO} permission.</p>

 * {@link android.Manifest.permission#RECORD_AUDIO} permission. Developers

 * should set the audio mode to {@link AudioManager#MODE_IN_COMMUNICATION}

 * using {@link AudioManager#setMode(int)} and change it back when none of

 * the AudioGroups is in use.</p>

 *

 * @see AudioStream

 * @hide

public class AudioGroup {

    /**

     * This mode is similar to {@link #MODE_NORMAL} except the speaker and

     * the microphone are disabled.

     * the microphone are both disabled.

     */

    public static final int MODE_ON_HOLD = 0;

    /**

     * This mode is similar to {@link #MODE_NORMAL} except the microphone is

     * muted.

     * disabled.

     */

    public static final int MODE_MUTED = 1;

    private native void nativeSetMode(int mode);

    // Package-private method used by AudioStream.join().

    void add(AudioStream stream, AudioCodec codec, int dtmfType) {

        synchronized (this) {

    synchronized void add(AudioStream stream, AudioCodec codec, int dtmfType) {

        if (!mStreams.containsKey(stream)) {

            try {

                int socket = stream.dup();

            }

        }

    }

    }

    private native void nativeAdd(int mode, int socket, String remoteAddress,

            int remotePort, String codecSpec, int dtmfType);

    // Package-private method used by AudioStream.join().

    void remove(AudioStream stream) {

        synchronized (this) {

    synchronized void remove(AudioStream stream) {

        Integer socket = mStreams.remove(stream);

        if (socket != null) {

            nativeRemove(socket);

        }

    }

    }

    private native void nativeRemove(int socket);

 * configured {@link AudioCodec}. On the other side, An {@link AudioGroup}

 * represents a local endpoint which mixes all the AudioStreams and optionally

 * interacts with the speaker and the microphone at the same time. The simplest

 * usage includes one for each endpoints. For other combinations, users should

 * be aware of the limitations described in {@link AudioGroup}.

 * usage includes one for each endpoints. For other combinations, developers

 * should be aware of the limitations described in {@link AudioGroup}.

 *

 * <p>An AudioStream becomes busy when it joins an AudioGroup. In this case most

 * of the setter methods are disabled. This is designed to ease the task of