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Commit 49c34acb authored by Glenn Kasten's avatar Glenn Kasten Committed by Jean-Michel Trivi
Browse files

Fix race condition in initializing downmix 

The code that initializes downmix GUID searches for an effect of
the right type.  If two or more AudioMixers are created, there is a
possibility that the GUID will temporarily have the wrong value.

Now the initialization is only done once, regardless of how many
AudioMixers there are.

Other minor changes:
 - use naming convention of leading 's' for static member variables
 - log message for no downmix effect is now a warning instead of an error,
   since it is not an error until there is actual content to downmix
   without a downmix effect

Change-Id: I33ab0e51cf9d24ecaf8ae868883736b0772178c4
parent d21952fe

services/audioflinger/AudioMixer.cpp

+26 −25
Original line number Diff line number Diff line
@@ -90,9 +90,9 @@ void AudioMixer::DownmixerBufferProvider::releaseBuffer(AudioBufferProvider::Buf 




// ----------------------------------------------------------------------------

bool AudioMixer::isMultichannelCapable = false;

bool AudioMixer::sIsMultichannelCapable = false;



effect_descriptor_t AudioMixer::dwnmFxDesc;

effect_descriptor_t AudioMixer::sDwnmFxDesc;



// Ensure mConfiguredNames bitmask is initialized properly on all architectures.

// The value of 1 << x is undefined in C when x >= 32.
@@ -136,27 +136,6 @@ AudioMixer::AudioMixer(size_t frameCount, uint32_t sampleRate, uint32_t maxNumTr 
        t++;

    }



    // find multichannel downmix effect if we have to play multichannel content

    uint32_t numEffects = 0;

    int ret = EffectQueryNumberEffects(&numEffects);

    if (ret != 0) {

        ALOGE("AudioMixer() error %d querying number of effects", ret);

        return;

    }

    ALOGV("EffectQueryNumberEffects() numEffects=%d", numEffects);



    for (uint32_t i = 0 ; i < numEffects ; i++) {

        if (EffectQueryEffect(i, &dwnmFxDesc) == 0) {

            ALOGV("effect %d is called %s", i, dwnmFxDesc.name);

            if (memcmp(&dwnmFxDesc.type, EFFECT_UIID_DOWNMIX, sizeof(effect_uuid_t)) == 0) {

                ALOGI("found effect \"%s\" from %s",

                        dwnmFxDesc.name, dwnmFxDesc.implementor);

                isMultichannelCapable = true;

                break;

            }

        }

    }

    ALOGE_IF(!isMultichannelCapable, "unable to find downmix effect");

}



AudioMixer::~AudioMixer()
@@ -276,13 +255,13 @@ status_t AudioMixer::prepareTrackForDownmix(track_t* pTrack, int trackName) 
    DownmixerBufferProvider* pDbp = new DownmixerBufferProvider();

    int32_t status;



    if (!isMultichannelCapable) {

    if (!sIsMultichannelCapable) {

        ALOGE("prepareTrackForDownmix(%d) fails: mixer doesn't support multichannel content",

                trackName);

        goto noDownmixForActiveTrack;

    }



    if (EffectCreate(&dwnmFxDesc.uuid,

    if (EffectCreate(&sDwnmFxDesc.uuid,

            pTrack->sessionId /*sessionId*/, -2 /*ioId not relevant here, using random value*/,

            &pDbp->mDownmixHandle/*pHandle*/) != 0) {

        ALOGE("prepareTrackForDownmix(%d) fails: error creating downmixer effect", trackName);
@@ -1459,6 +1438,28 @@ int64_t AudioMixer::calculateOutputPTS(const track_t& t, int64_t basePTS, 
{

    LocalClock lc;

    sLocalTimeFreq = lc.getLocalFreq();



    // find multichannel downmix effect if we have to play multichannel content

    uint32_t numEffects = 0;

    int ret = EffectQueryNumberEffects(&numEffects);

    if (ret != 0) {

        ALOGE("AudioMixer() error %d querying number of effects", ret);

        return;

    }

    ALOGV("EffectQueryNumberEffects() numEffects=%d", numEffects);



    for (uint32_t i = 0 ; i < numEffects ; i++) {

        if (EffectQueryEffect(i, &sDwnmFxDesc) == 0) {

            ALOGV("effect %d is called %s", i, sDwnmFxDesc.name);

            if (memcmp(&sDwnmFxDesc.type, EFFECT_UIID_DOWNMIX, sizeof(effect_uuid_t)) == 0) {

                ALOGI("found effect \"%s\" from %s",

                        sDwnmFxDesc.name, sDwnmFxDesc.implementor);

                sIsMultichannelCapable = true;

                break;

            }

        }

    }

    ALOGW_IF(!sIsMultichannelCapable, "unable to find downmix effect");

}



// ----------------------------------------------------------------------------

services/audioflinger/AudioMixer.h

+2 −2
Original line number Diff line number Diff line
@@ -256,9 +256,9 @@ private: 
    state_t         mState __attribute__((aligned(32)));



    // effect descriptor for the downmixer used by the mixer

    static effect_descriptor_t dwnmFxDesc;

    static effect_descriptor_t sDwnmFxDesc;

    // indicates whether a downmix effect has been found and is usable by this mixer

    static bool                isMultichannelCapable;

    static bool                sIsMultichannelCapable;



    // Call after changing either the enabled status of a track, or parameters of an enabled track.

    // OK to call more often than that, but unnecessary.