Android平台GB28181设备接入，语音广播功能非常重要，本文要介绍的，不是语音广播的流程，语音广播流程，之前的blog也有非常详细的分享，感兴趣的可以参考官方规范书的交互流程：

语音广播这块，有开发者提出这样的诉求，如何适时调节语音广播的音量？

因为我们的语音广播，audio的播放，是基于我们RTMP、RTSP直播播放模块设计实现的，对应的接口如下：

	/*** 设置播放音量** @param handle: return value from SmartPlayerOpen()** @param volume: 范围是[0, 100], 0是静音，100是最大音量, 默认是100** @return {0} if successful*/public native int SmartPlayerSetAudioVolume(long handle, int volume);

如果需要实时调节音量，只要加个音量调节的SeekBar即可：

        audioVolumeBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {@Overridepublic void onProgressChanged(SeekBar seekBar, int i, boolean b) {}@Overridepublic void onStartTrackingTouch(SeekBar seekBar) {}@Overridepublic void onStopTrackingTouch(SeekBar seekBar) {curAudioVolume = seekBar.getProgress();audioVolumeText.setText("当前音量: " + curAudioVolume);if(playerHandle != 0){libPlayer.SmartPlayerSetAudioVolume(playerHandle, curAudioVolume);}}});

如果需要在启动播放的时候，给个默认的初始音量，可以在StartAudioPlay()的时候，设置即可：

    private boolean startAudioPlay() {if (player_handle_ != 0 )return false;player_handle_ = lib_player_.SmartPlayerOpen(context_);if (player_handle_ == 0)return false;lib_player_.SetSmartPlayerEventCallbackV2(player_handle_,new EventHandePlayerV2());// 缓存大小可以调整lib_player_.SmartPlayerSetBuffer(player_handle_, 0);// lib_player_.SmartPlayerSetFastStartup(player_handle_, 0);// set report download speed(默认2秒一次回调 用户可自行调整report间隔)lib_player_.SmartPlayerSetReportDownloadSpeed(player_handle_, 1, 20);lib_player_.SmartPlayerClearRtpReceivers(player_handle_);lib_player_.SmartPlayerAddRtpReceiver(player_handle_, rtp_receiver_handle_);lib_player_.SmartPlayerSetSurface(player_handle_, null);// lib_player_.SmartPlayerSetRenderScaleMode(player_handle_, 1);lib_player_.SmartPlayerSetAudioOutputType(player_handle_, 1);lib_player_.SmartPlayerSetMute(player_handle_, 0);lib_player_.SmartPlayerSetAudioVolume(player_handle_, 100);lib_player_.SmartPlayerSetExternalAudioOutput(player_handle_, new PlayerExternalPCMOutput());lib_player_.SmartPlayerSetUrl(player_handle_, "rtp:--/-/ntinternal/rtpreceiver/implemention0");if (0 != lib_player_.SmartPlayerStartPlay(player_handle_)) {lib_player_.SmartPlayerClose(player_handle_);player_handle_ = 0;Log.e(TAG,  "start audio paly failed");return false;}lib_player_.SmartPlayerSetAudioDataCallback(player_handle_, new PlayerAudioDataOutput());lib_player_.SmartPlayerSetPullStreamAudioTranscodeAAC(player_handle_, 0);if (0 ==lib_player_.SmartPlayerStartPullStream(player_handle_) ) {// 启动定时器，长时间收不到音频数据，则停止播放，发送BYElast_received_audio_data_time_.set(SystemClock.elapsedRealtime());handler_.postDelayed(new AudioPlayerPCMTimer(player_handle_), AudioPlayerPCMTimer.INTERVAL_MS);}return true;}

如果需要静音，audio volume设置为0即可，以上是大概的接口设计和调用逻辑，感兴趣的开发者，可以自行尝试。