WebRTC VoiceEngine综合应用示例（二）——音频通话的基本流程（转）

下面将以实现一个音频通话功能为示例详细介绍VoiceEngine的使用，在文末将附上相应源码的下载地址。这里参考的是voiceenginevoe_cmd_test。

第一步是创建VoiceEngine和相关的sub-apis

// Create VoiceEngine related instance
webrtc::VoiceEngine* ptrVoE = NULL;
ptrVoE = webrtc::VoiceEngine::Create();

webrtc::VoEBase* ptrVoEBase = NULL;
ptrVoEBase = webrtc::VoEBase::GetInterface(ptrVoE);

webrtc::VoECodec* ptrVoECodec = NULL;
ptrVoECodec = webrtc::VoECodec::GetInterface(ptrVoE);

webrtc::VoEAudioProcessing* ptrVoEAp = NULL;
ptrVoEAp = webrtc::VoEAudioProcessing::GetInterface(ptrVoE);

webrtc::VoEVolumeControl* ptrVoEVolume = NULL;
ptrVoEVolume = webrtc::VoEVolumeControl::GetInterface(ptrVoE);

webrtc::VoENetwork* ptrVoENetwork = NULL;
ptrVoENetwork = webrtc::VoENetwork::GetInterface(ptrVoE);

webrtc::VoEFile* ptrVoEFile = NULL;
ptrVoEFile = webrtc::VoEFile::GetInterface(ptrVoE);

webrtc::VoEHardware* ptrVoEHardware = NULL;
ptrVoEHardware = webrtc::VoEHardware::GetInterface(ptrVoE);

然后可以选择设置tracefile的路径，这里我们还会对麦克风以及回放的声音做一个录制，所以也一并指明路径。

//Set Trace File and Record File
const std::string trace_filename = "webrtc_trace.txt";
VoiceEngine::SetTraceFilter(kTraceAll);
error = VoiceEngine::SetTraceFile(trace_filename.c_str());
if (error != 0)
{
    printf("ERROR in VoiceEngine::SetTraceFile
");
    return error;
}
error = VoiceEngine::SetTraceCallback(NULL);
if (error != 0)
{
    printf("ERROR in VoiceEngine::SetTraceCallback
");
    return error;
}
const std::string play_filename = "recorded_playout.wav";
const std::string mic_filename = "recorded_mic.wav";

接下来是初始化，获取VoiceEngine的版本号

//Init
error = ptrVoEBase->Init();
if (error != 0)
{
    printf("ERROR in VoEBase::Init
");
    return error;
}
error = ptrVoEBase->RegisterVoiceEngineObserver(my_observer);
if (error != 0)
{
    printf("ERROR in VoEBase:;RegisterVoiceEngineObserver
");
    return error;
}
printf("Version
");
char tmp[1024];
error = ptrVoEBase->GetVersion(tmp);
if (error != 0)
{
    printf("ERROR in VoEBase::GetVersion
");
    return error;
}
printf("%s
", tmp);

这里同时还注册了一个VoiceEngineObserver对象，可以根据相应的error code输出信息，比如当检测到键盘敲击的噪音时会给出提示。这个类的定义如下：

class MyObserver : public VoiceEngineObserver
{
public:
    virtual void CallbackOnError(int channel, int err_code);
};

void MyObserver::CallbackOnError(int channel, int err_code)
{
    // Add printf for other error codes here
    if (err_code == VE_TYPING_NOISE_WARNING)
    {
        printf("  TYPING NOISE DETECTED 
");
    }
    else if (err_code == VE_TYPING_NOISE_OFF_WARNING)
    {
        printf("  TYPING NOISE OFF DETECTED 
");
    }
    else if (err_code == VE_RECEIVE_PACKET_TIMEOUT)
    {
        printf("  RECEIVE PACKET TIMEOUT 
");
    }
    else if (err_code == VE_PACKET_RECEIPT_RESTARTED)
    {
        printf("  PACKET RECEIPT RESTARTED 
");
    }
    else if (err_code == VE_RUNTIME_PLAY_WARNING)
    {
        printf("  RUNTIME PLAY WARNING 
");
    }
    else if (err_code == VE_RUNTIME_REC_WARNING)
    {
        printf("  RUNTIME RECORD WARNING 
");
    }
    else if (err_code == VE_SATURATION_WARNING)
    {
        printf("  SATURATION WARNING 
");
    }
    else if (err_code == VE_RUNTIME_PLAY_ERROR)
    {
        printf("  RUNTIME PLAY ERROR 
");
    }
    else if (err_code == VE_RUNTIME_REC_ERROR)
    {
        printf("  RUNTIME RECORD ERROR 
");
    }
    else if (err_code == VE_REC_DEVICE_REMOVED)
    {
        printf("  RECORD DEVICE REMOVED 
");
    }
}

以上完成了前期准备的工作，下面首先开始对网络的设置。如果是在本机上进行测试的话，ip地址直接写127.0.0.1即可，同时要注意的是，remote port和local port要一致。

//Network Settings
int audiochannel;
audiochannel = ptrVoEBase->CreateChannel();
if (audiochannel < 0)
{
    printf("ERROR in VoEBase::CreateChannel
");
    return audiochannel;
}
VoiceChannelTransport* voice_channel_transport = new VoiceChannelTransport(ptrVoENetwork, audiochannel);
char ip[64] = "127.0.0.1";
int rPort = 800;//remote port
int lPort = 800;//local port
error = voice_channel_transport->SetSendDestination(ip, rPort);
if (error != 0)
{
    printf("ERROR in set send ip and port
");
    return error;
}
error = voice_channel_transport->SetLocalReceiver(lPort);
if (error != 0)
{
    printf("ERROR in set receiver and port
");
    return error;
}

上面出现的VoiceChannelTransport类的定义如下

// Helper class for VoiceEngine tests.
class VoiceChannelTransport : public webrtc::test::UdpTransportData
{
public:
    VoiceChannelTransport(VoENetwork* voe_network, int channel);

    virtual ~VoiceChannelTransport();

    // Start implementation of UdpTransportData.
    void IncomingRTPPacket(const int8_t* incoming_rtp_packet,
        const size_t packet_length,
        const char* /*from_ip*/,
        const uint16_t /*from_port*/) override;

    void IncomingRTCPPacket(const int8_t* incoming_rtcp_packet,
        const size_t packet_length,
        const char* /*from_ip*/,
        const uint16_t /*from_port*/) override;
    // End implementation of UdpTransportData.

    // Specifies the ports to receive RTP packets on.
    int SetLocalReceiver(uint16_t rtp_port);

    // Specifies the destination port and IP address for a specified channel.
    int SetSendDestination(const char* ip_address, uint16_t rtp_port);

private:
    int channel_;
    VoENetwork* voe_network_;
    webrtc::test::UdpTransport* socket_transport_;
};


VoiceChannelTransport::VoiceChannelTransport(VoENetwork* voe_network,
    int channel)
    : channel_(channel),
    voe_network_(voe_network)
{
    uint8_t socket_threads = 1;
    socket_transport_ = webrtc::test::UdpTransport::Create(channel, socket_threads);
    int registered = voe_network_->RegisterExternalTransport(channel, *socket_transport_);
#if !defined(WEBRTC_ANDROID) && !defined(WEBRTC_IOS)
    if (registered != 0)
        return;
#else
    assert(registered == 0);
#endif
}

VoiceChannelTransport::~VoiceChannelTransport()
{
    voe_network_->DeRegisterExternalTransport(channel_);
    webrtc::test::UdpTransport::Destroy(socket_transport_);
}

void VoiceChannelTransport::IncomingRTPPacket(
    const int8_t* incoming_rtp_packet,
    const size_t packet_length,
    const char* /*from_ip*/,
    const uint16_t /*from_port*/)
{
    voe_network_->ReceivedRTPPacket(channel_, incoming_rtp_packet, packet_length, PacketTime());
}

void VoiceChannelTransport::IncomingRTCPPacket(
    const int8_t* incoming_rtcp_packet,
    const size_t packet_length,
    const char* /*from_ip*/,
    const uint16_t /*from_port*/)
{
    voe_network_->ReceivedRTCPPacket(channel_, incoming_rtcp_packet, packet_length);
}

int VoiceChannelTransport::SetLocalReceiver(uint16_t rtp_port)
{
    static const int kNumReceiveSocketBuffers = 500;
    int return_value = socket_transport_->InitializeReceiveSockets(this, rtp_port);
    if (return_value == 0)
    {
        return socket_transport_->StartReceiving(kNumReceiveSocketBuffers);
    }
    return return_value;
}

int VoiceChannelTransport::SetSendDestination(const char* ip_address, uint16_t rtp_port)
{
    return socket_transport_->InitializeSendSockets(ip_address, rtp_port);
}

完成了网络的设置后，进行编解码器的设置。这里简单的由用户选择使用哪一个编码器，当然还可以进一步对编码器的参数进行设置

//Setup Codecs
CodecInst codec_params;
CodecInst cinst;
for (int i = 0; i < ptrVoECodec->NumOfCodecs(); ++i)
{
    int error = ptrVoECodec->GetCodec(i, codec_params);
    if (error != 0)
    {
        printf("ERROR in VoECodec::GetCodec
");
        return error;
    }
    printf("%2d. %3d  %s/%d/%d 
", i, codec_params.pltype, codec_params.plname, codec_params.plfreq, codec_params.channels);
}
printf("Select send codec: ");
int codec_selection;
scanf("%i", &codec_selection);
ptrVoECodec->GetCodec(codec_selection, cinst);
error = ptrVoECodec->SetSendCodec(audiochannel, cinst);
if (error != 0)
{
    printf("ERROR in VoECodec::SetSendCodec
");
    return error;
}

接下来进行录制设备和播放设备的设置

//Setup Devices
int rd(-1), pd(-1);
error = ptrVoEHardware->GetNumOfRecordingDevices(rd);
if (error != 0)
{
    printf("ERROR in VoEHardware::GetNumOfRecordingDevices
");
    return error;
}
error = ptrVoEHardware->GetNumOfPlayoutDevices(pd);
if (error != 0)
{
    printf("ERROR in VoEHardware::GetNumOfPlayoutDevices
");
    return error;
}

char dn[128] = { 0 };
char guid[128] = { 0 };
printf("
Playout devices (%d): 
", pd);
for (int j = 0; j < pd; ++j)
{
    error = ptrVoEHardware->GetPlayoutDeviceName(j, dn, guid);
    if (error != 0)
    {
        printf("ERROR in VoEHardware::GetPlayoutDeviceName
");
        return error;
    }
    printf("  %d: %s 
", j, dn);
}

printf("Recording devices (%d): 
", rd);
for (int j = 0; j < rd; ++j)
{
    error = ptrVoEHardware->GetRecordingDeviceName(j, dn, guid);
    if (error != 0)
    {
        printf("ERROR in VoEHardware::GetRecordingDeviceName
");
        return error;
    }
    printf("  %d: %s 
", j, dn);
}

printf("Select playout device: ");
scanf("%d", &pd);
error = ptrVoEHardware->SetPlayoutDevice(pd);
if (error != 0)
{
    printf("ERROR in VoEHardware::SetPlayoutDevice
");
    return error;
}
printf("Select recording device: ");
scanf("%d", &rd);
getchar();
error = ptrVoEHardware->SetRecordingDevice(rd);
if (error != 0)
{
    printf("ERROR in VoEHardware::SetRecordingDevice
");
    return error;
}

然后对音频预处理功能进行设置，这里作为示例，把各种预处理功能都enable了

//Audio Processing
error = ptrVoECodec->SetVADStatus(0, 1);//FIX:why not use audio channel
if (error != 0)
{
    printf("ERROR in VoECodec::SetVADStatus
");
    return error;
}
error = ptrVoEAp->SetAgcStatus(1);
if (error != 0)
{
    printf("ERROR in VoEAudioProcess::SetAgcStatus
");
    return error;
}
error = ptrVoEAp->SetEcStatus(1);
if (error != 0)
{
    printf("ERROR in VoEAudioProcess::SetEcStatus
");
    return error;
}
error = ptrVoEAp->SetNsStatus(1);
if (error != 0)
{
    printf("ERROR in VoEAudioProcess::SetNsStatus
");
    return error;
}
error = ptrVoEAp->SetRxAgcStatus(audiochannel, 1);
if (error != 0)
{
    printf("ERROR in VoEAudioProcess::SetRxAgcStatus
");
    return error;
}
error = ptrVoEAp->SetRxNsStatus(audiochannel, 1);
if (error != 0)
{
    printf("ERROR in VoEAudioProcess::SetRxNsStatus
");
    return error;
}

至此，就可以开始发送、接收、录制了

//Start Receive
error = ptrVoEBase->StartReceive(audiochannel);
if (error != 0)
{
    printf("ERROR in VoEBase::StartReceive
");
    return error;
}
//Start Playout
error = ptrVoEBase->StartPlayout(audiochannel);
if (error != 0)
{
    printf("ERROR in VoEBase::StartPlayout
");
    return error;
}
//Start Send
error = ptrVoEBase->StartSend(audiochannel);
if (error != 0)
{
    printf("ERROR in VoEBase::StartSend
");
    return error;
}
//Start Record
error = ptrVoEFile->StartRecordingMicrophone(mic_filename.c_str());
if (error != 0)
{
    printf("ERROR in VoEFile::StartRecordingMicrophone
");
    return error;
}
error = ptrVoEFile->StartRecordingPlayout(audiochannel, play_filename.c_str());
if (error != 0)
{
    printf("ERROR in VoEFile::StartRecordingPlayout
");
    return error;
}

在通话结束之后，还需要进行相应的stop elease

//Stop Record
error = ptrVoEFile->StopRecordingMicrophone();
if (error != 0)
{
    printf("ERROR in VoEFile::StopRecordingMicrophone
");
    return error;
}
error = ptrVoEFile->StopRecordingPlayout(audiochannel);
if (error != 0)
{
    printf("ERROR in VoEFile::StopRecordingPlayout
");
    return error;
}
//Stop Receive
error = ptrVoEBase->StopReceive(audiochannel);
if (error != 0)
{
    printf("ERROR in VoEBase::StopReceive
");
    return error;
}
//Stop Send
error = ptrVoEBase->StopSend(audiochannel);
if (error != 0)
{
    printf("ERROR in VoEBase::StopSend
");
    return error;
}
//Stop Playout
error = ptrVoEBase->StopPlayout(audiochannel);
if (error != 0)
{
    printf("ERROR in VoEBase::StopPlayout
");
    return error;
}
//Delete Channel
error = ptrVoEBase->DeleteChannel(audiochannel);
if (error != 0)
{
    printf("ERROR in VoEBase::DeleteChannel
");
    return error;
}

delete voice_channel_transport;

ptrVoEBase->DeRegisterVoiceEngineObserver();
error = ptrVoEBase->Terminate();
if (error != 0)
{
    printf("ERROR in VoEBase::Terminate
");
    return error;
}

int remainingInterfaces = 0;
remainingInterfaces += ptrVoEBase->Release();
remainingInterfaces = ptrVoECodec->Release();
remainingInterfaces += ptrVoEVolume->Release();
remainingInterfaces += ptrVoEFile->Release();
remainingInterfaces += ptrVoEAp->Release();
remainingInterfaces += ptrVoEHardware->Release();
remainingInterfaces += ptrVoENetwork->Release();


/*if (remainingInterfaces > 0)
{
printf("ERROR: Could not release all interfaces
");
return -1;
}*/

bool deleted = webrtc::VoiceEngine::Delete(ptrVoE);
if (deleted == false)
{
    printf("ERROR in VoiceEngine::Delete
");
    return -1;
}

需要注意的是，这里remainingInterfaces最后不会为0，因为我们没有用到VoiceEngine的全部sub-apis。 

至此，就实现了一个音频通话的功能。本项目源代码下载地址。github地址。

原文转自 http://blog.csdn.net/nonmarking/article/details/50577860