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Commit 3cf71376 authored by Chia-chi Yeh's avatar Chia-chi Yeh
Browse files

RTP: Send silence packets on idle streams for every second. 

Originally a stream does not send packets when it is receive-only or there is
nothing to mix. However, this causes some problems with certain firewalls and
proxies. A firewall might remove a port mapping when there is no outgoing
packet for a preiod of time, and a proxy might wait for incoming packets from
both sides before start forwarding. To solve these problems, we send out a
silence packet on the stream for every second. It should be good enough to
keep the stream alive with relatively low resources.

Bug: 3119690
Change-Id: Ib9c55e5dddfba28928bd9b376832b68bda24c0e4
parent 8f49c025

voip/jni/rtp/AudioGroup.cpp

+48 −32
Original line number Diff line number Diff line
@@ -63,6 +63,14 @@ int gRandom = -1; 
// real jitter buffer. For a stream at 8000Hz it takes 8192 bytes. These numbers

// are chosen by experiments and each of them can be adjusted as needed.



// Originally a stream does not send packets when it is receive-only or there is

// nothing to mix. However, this causes some problems with certain firewalls and

// proxies. A firewall might remove a port mapping when there is no outgoing

// packet for a preiod of time, and a proxy might wait for incoming packets from

// both sides before start forwarding. To solve these problems, we send out a

// silence packet on the stream for every second. It should be good enough to

// keep the stream alive with relatively low resources.



// Other notes:

// + We use elapsedRealtime() to get the time. Since we use 32bit variables

//   instead of 64bit ones, comparison must be done by subtraction.
@@ -110,7 +118,7 @@ private: 
    int mSampleRate;

    int mSampleCount;

    int mInterval;

    int mLogThrottle;

    int mKeepAlive;



    int16_t *mBuffer;

    int mBufferMask;
@@ -262,12 +270,8 @@ void AudioStream::encode(int tick, AudioStream *chain) 
    ++mSequence;

    mTimestamp += mSampleCount;



    if (mMode == RECEIVE_ONLY) {

        return;

    }



    // If there is an ongoing DTMF event, send it now.

    if (mDtmfEvent != -1) {

    if (mMode != RECEIVE_ONLY && mDtmfEvent != -1) {

        int duration = mTimestamp - mDtmfStart;

        // Make sure duration is reasonable.

        if (duration >= 0 && duration < mSampleRate * 100) {
@@ -289,9 +293,17 @@ void AudioStream::encode(int tick, AudioStream *chain) 
        mDtmfEvent = -1;

    }



    // It is time to mix streams.

    bool mixed = false;

    int32_t buffer[mSampleCount + 3];

    int16_t samples[mSampleCount];

    if (mMode == RECEIVE_ONLY) {

        if ((mTick ^ mKeepAlive) >> 10 == 0) {

            return;

        }

        mKeepAlive = mTick;

        memset(samples, 0, sizeof(samples));

    } else {

        // Mix all other streams.

        bool mixed = false;

        memset(buffer, 0, sizeof(buffer));

        while (chain) {

            if (chain != this &&
@@ -300,16 +312,9 @@ void AudioStream::encode(int tick, AudioStream *chain) 
            }

            chain = chain->mNext;

        }

    if (!mixed) {

        if ((mTick ^ mLogThrottle) >> 10) {

            mLogThrottle = mTick;

            LOGV("stream[%d] no data", mSocket);

        }

        return;

    }



    // Cook the packet and send it out.

    int16_t samples[mSampleCount];

        if (mixed) {

            // Saturate into 16 bits.

            for (int i = 0; i < mSampleCount; ++i) {

                int32_t sample = buffer[i];

                if (sample < -32768) {
@@ -320,12 +325,23 @@ void AudioStream::encode(int tick, AudioStream *chain) 
                }

                samples[i] = sample;

            }

        } else {

            if ((mTick ^ mKeepAlive) >> 10 == 0) {

                return;

            }

            mKeepAlive = mTick;

            memset(samples, 0, sizeof(samples));

            LOGV("stream[%d] no data", mSocket);

        }

    }



    if (!mCodec) {

        // Special case for device stream.

        send(mSocket, samples, sizeof(samples), MSG_DONTWAIT);

        return;

    }



    // Cook the packet and send it out.

    buffer[0] = htonl(mCodecMagic | mSequence);

    buffer[1] = htonl(mTimestamp);

    buffer[2] = mSsrc;
@@ -883,7 +899,7 @@ void add(JNIEnv *env, jobject thiz, jint mode, 
    int codecType = -1;

    char codecName[16];

    int sampleRate = -1;

    sscanf(codecSpec, "%d %[^/]%*c%d", &codecType, codecName, &sampleRate);

    sscanf(codecSpec, "%d %15[^/]%*c%d", &codecType, codecName, &sampleRate);

    codec = newAudioCodec(codecName);

    int sampleCount = (codec ? codec->set(sampleRate, codecSpec) : -1);

    env->ReleaseStringUTFChars(jCodecSpec, codecSpec);