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Commit 33ff89ba authored by Phil Burk's avatar Phil Burk
Browse files

AudioTrack: lower Java latency 



Add AUDIO_FLAG_LOW_LATENCY to enable Fast track.

Change-Id: Ib1bff635afaa57af7754cb751b57c6afc4c2ab2b
Bug: 21019153
Signed-off-by: default avatarPhil Burk <philburk@google.com>
parent e0db3086

include/media/AudioTrack.h

+1 −0
Original line number Diff line number Diff line
@@ -811,6 +811,7 @@ protected: 
    audio_io_handle_t       mOutput;                // returned by AudioSystem::getOutput()



    sp<AudioTrackThread>    mAudioTrackThread;

    bool                    mThreadCanCallJava;



    float                   mVolume[2];

    float                   mSendLevel;

media/libmedia/AudioTrack.cpp

+22 −9
Original line number Diff line number Diff line
@@ -288,6 +288,8 @@ status_t AudioTrack::set( 
          streamType, sampleRate, format, channelMask, frameCount, flags, notificationFrames,

          sessionId, transferType, uid, pid);



    mThreadCanCallJava = threadCanCallJava;



    switch (transferType) {

    case TRANSFER_DEFAULT:

        if (sharedBuffer != 0) {
@@ -356,6 +358,9 @@ status_t AudioTrack::set( 
        if ((mAttributes.flags & AUDIO_FLAG_HW_AV_SYNC) != 0) {

            flags = (audio_output_flags_t)(flags | AUDIO_OUTPUT_FLAG_HW_AV_SYNC);

        }

        if ((mAttributes.flags & AUDIO_FLAG_LOW_LATENCY) != 0) {

            flags = (audio_output_flags_t) (flags | AUDIO_OUTPUT_FLAG_FAST);

        }

    }



    // these below should probably come from the audioFlinger too...
@@ -1170,21 +1175,27 @@ status_t AudioTrack::createTrack_l() 
    }

    // Client decides whether the track is TIMED (see below), but can only express a preference

    // for FAST.  Server will perform additional tests.

    if ((mFlags & AUDIO_OUTPUT_FLAG_FAST) && !((

    if (mFlags & AUDIO_OUTPUT_FLAG_FAST) {

        bool useCaseAllowed =

            // either of these use cases:

            // use case 1: shared buffer

            (mSharedBuffer != 0) ||

            // use case 2: callback transfer mode

            (mTransfer == TRANSFER_CALLBACK) ||

            // use case 3: obtain/release mode

            (mTransfer == TRANSFER_OBTAIN)) &&

            // matching sample rate

            (mSampleRate == mAfSampleRate))) {

        ALOGW("AUDIO_OUTPUT_FLAG_FAST denied by client; transfer %d, track %u Hz, output %u Hz",

            (mTransfer == TRANSFER_OBTAIN) ||

            // use case 4: synchronous write

            ((mTransfer == TRANSFER_SYNC) && mThreadCanCallJava);

        // sample rates must also match

        bool fastAllowed = useCaseAllowed && (mSampleRate == mAfSampleRate);

        if (!fastAllowed) {

            ALOGW("AUDIO_OUTPUT_FLAG_FAST denied by client; transfer %d,"

                "track %u Hz, output %u Hz",

                mTransfer, mSampleRate, mAfSampleRate);

            // once denied, do not request again if IAudioTrack is re-created

            mFlags = (audio_output_flags_t) (mFlags & ~AUDIO_OUTPUT_FLAG_FAST);

        }

    }



    // The client's AudioTrack buffer is divided into n parts for purpose of wakeup by server, where

    //  n = 1   fast track with single buffering; nBuffering is ignored
@@ -1254,7 +1265,7 @@ status_t AudioTrack::createTrack_l() 
    pid_t tid = -1;

    if (mFlags & AUDIO_OUTPUT_FLAG_FAST) {

        trackFlags |= IAudioFlinger::TRACK_FAST;

        if (mAudioTrackThread != 0) {

        if (mAudioTrackThread != 0 && !mThreadCanCallJava) {

            tid = mAudioTrackThread->getTid();

        }

    }
@@ -1328,7 +1339,9 @@ status_t AudioTrack::createTrack_l() 
    if (mFlags & AUDIO_OUTPUT_FLAG_FAST) {

        if (trackFlags & IAudioFlinger::TRACK_FAST) {

            ALOGV("AUDIO_OUTPUT_FLAG_FAST successful; frameCount %zu", frameCount);

            if (!mThreadCanCallJava) {

                mAwaitBoost = true;

            }

        } else {

            ALOGV("AUDIO_OUTPUT_FLAG_FAST denied by server; frameCount %zu", frameCount);

            // once denied, do not request again if IAudioTrack is re-created