Android Audio程式碼分析16 - testPlaybackHeadPositionAfterPause函數

play, stop, flush這幾個函數，今天來看看pause函數。

*****************************************源碼*************************************************
    //Test case 4: getPlaybackHeadPosition() is > 0 after play(); pause();
    @LargeTest
    public void testPlaybackHeadPositionAfterPause() throws Exception {
        // constants for test
        final String TEST_NAME = "testPlaybackHeadPositionAfterPause";
        final int TEST_SR = 22050;
        final int TEST_CONF = AudioFormat.CHANNEL_OUT_STEREO;
        final int TEST_FORMAT = AudioFormat.ENCODING_PCM_16BIT;
        final int TEST_MODE = AudioTrack.MODE_STREAM;
        final int TEST_STREAM_TYPE = AudioManager.STREAM_MUSIC;
       
        //-------- initialization --------------
        int minBuffSize = AudioTrack.getMinBufferSize(TEST_SR, TEST_CONF, TEST_FORMAT);
        AudioTrack track = new AudioTrack(TEST_STREAM_TYPE, TEST_SR, TEST_CONF, TEST_FORMAT,
                minBuffSize, TEST_MODE);
        byte data[] = new byte[minBuffSize/2];
        //--------    test        --------------
        assumeTrue(TEST_NAME, track.getState() == AudioTrack.STATE_INITIALIZED);
        track.write(data, 0, data.length);
        track.write(data, 0, data.length);
        track.play();
        Thread.sleep(100);
        track.pause();
        int pos = track.getPlaybackHeadPosition();
        log(TEST_NAME, "position ="+ pos);
        assertTrue(TEST_NAME, pos > 0);
        //-------- tear down      --------------
        track.release();
    }
**********************************************************************************************
源碼路徑：
frameworks\base\media\tests\mediaframeworktest\src\com\android\mediaframeworktest\functional\MediaAudioTrackTest.java

#######################說明################################
    //Test case 4: getPlaybackHeadPosition() is > 0 after play(); pause();
    @LargeTest
    public void testPlaybackHeadPositionAfterPause() throws Exception {
        // constants for test
        final String TEST_NAME = "testPlaybackHeadPositionAfterPause";
        final int TEST_SR = 22050;
        final int TEST_CONF = AudioFormat.CHANNEL_OUT_STEREO;
        final int TEST_FORMAT = AudioFormat.ENCODING_PCM_16BIT;
        final int TEST_MODE = AudioTrack.MODE_STREAM;
        final int TEST_STREAM_TYPE = AudioManager.STREAM_MUSIC;
       
        //-------- initialization --------------
        int minBuffSize = AudioTrack.getMinBufferSize(TEST_SR, TEST_CONF, TEST_FORMAT);
        AudioTrack track = new AudioTrack(TEST_STREAM_TYPE, TEST_SR, TEST_CONF, TEST_FORMAT,
                minBuffSize, TEST_MODE);
        byte data[] = new byte[minBuffSize/2];
        //--------    test        --------------
        assumeTrue(TEST_NAME, track.getState() == AudioTrack.STATE_INITIALIZED);
        track.write(data, 0, data.length);
        track.write(data, 0, data.length);
        track.play();
        Thread.sleep(100);
        track.pause();
++++++++++++++++++++++++++++++pause++++++++++++++++++++++++++++++++++
    /**
     * Pauses the playback of the audio data.
     * @throws IllegalStateException
     */
    public void pause()
    throws IllegalStateException {
        if (mState != STATE_INITIALIZED) {
            throw(new IllegalStateException("pause() called on uninitialized AudioTrack."));
        }
        //logd("pause()");

        // pause playback
        synchronized(mPlayStateLock) {
            native_pause();
+++++++++++++++++++++++++++++++android_media_AudioTrack_pause+++++++++++++++++++++++++++++++++
static void
android_media_AudioTrack_pause(JNIEnv *env, jobject thiz)
{
    AudioTrack *lpTrack = (AudioTrack *)env->GetIntField(
        thiz, javaAudioTrackFields.nativeTrackInJavaObj);
    if (lpTrack == NULL ) {
        jniThrowException(env, "java/lang/IllegalStateException",
            "Unable to retrieve AudioTrack pointer for pause()");
        return;
    }

    lpTrack->pause();
++++++++++++++++++++++++++++++AudioTrack::pause++++++++++++++++++++++++++++++++++
void AudioTrack::pause()
{
    LOGV("pause");
    if (android_atomic_and(~1, &mActive) == 1) {
// mAudioTrack在函數AudioTrack::createTrack中被賦值，其最終指向的其實是一個TrackHandle對象
        mAudioTrack->pause();
++++++++++++++++++++++++++++AudioFlinger::TrackHandle::pause++++++++++++++++++++++++++++++++++++
void AudioFlinger::TrackHandle::pause() {
    mTrack->pause();
++++++++++++++++++++++++++++AudioFlinger::PlaybackThread::Track::pause++++++++++++++++++++++++++++++++++++
void AudioFlinger::PlaybackThread::Track::pause()
{
    LOGV("pause(%d), calling thread %d", mName, IPCThreadState::self()->getCallingPid());
    sp<ThreadBase> thread = mThread.promote();
    if (thread != 0) {
        Mutex::Autolock _l(thread->mLock);
        if (mState == ACTIVE || mState == RESUMING) {
            mState = PAUSING;
            LOGV("ACTIVE/RESUMING => PAUSING (%d) on thread %p", mName, thread.get());
            if (!isOutputTrack()) {
++++++++++++++++++++++++++++isOutputTrack++++++++++++++++++++++++++++++++++++
            bool isOutputTrack() const {
                return (mStreamType == AudioSystem::NUM_STREAM_TYPES);
            }
----------------------------isOutputTrack------------------------------------
                thread->mLock.unlock();
// 在看stop代碼的時候已經看過函數AudioSystem::stopOutput
                AudioSystem::stopOutput(thread->id(),
                                        (AudioSystem::stream_type)mStreamType,
                                        mSessionId);
                thread->mLock.lock();
            }
        }
    }
}
----------------------------AudioFlinger::PlaybackThread::Track::pause------------------------------------
}
----------------------------AudioFlinger::TrackHandle::pause------------------------------------
    }
}
------------------------------AudioTrack::pause----------------------------------
}
-------------------------------android_media_AudioTrack_pause---------------------------------
            mPlayState = PLAYSTATE_PAUSED;
        }
    }
------------------------------pause----------------------------------
        int pos = track.getPlaybackHeadPosition();
        log(TEST_NAME, "position ="+ pos);
        assertTrue(TEST_NAME, pos > 0);
        //-------- tear down      --------------
        track.release();
++++++++++++++++++++++++++++++release++++++++++++++++++++++++++++++++++
    /**
     * Releases the native AudioTrack resources.
     */
    public void release() {
        // even though native_release() stops the native AudioTrack, we need to stop
        // AudioTrack subclasses too.
        try {
            stop();
        } catch(IllegalStateException ise) {
            // don't raise an exception, we're releasing the resources.
        }
        native_release();
+++++++++++++++++++++++++++++android_media_AudioTrack_native_release+++++++++++++++++++++++++++++++++++
static void android_media_AudioTrack_native_release(JNIEnv *env,  jobject thiz) {
      
    // do everything a call to finalize would
    android_media_AudioTrack_native_finalize(env, thiz);
+++++++++++++++++++++++++++++android_media_AudioTrack_native_finalize+++++++++++++++++++++++++++++++++++
static void android_media_AudioTrack_native_finalize(JNIEnv *env,  jobject thiz) {
    //LOGV("android_media_AudioTrack_native_finalize jobject: %x\n", (int)thiz);
      
    // delete the AudioTrack object
    AudioTrack *lpTrack = (AudioTrack *)env->GetIntField(
        thiz, javaAudioTrackFields.nativeTrackInJavaObj);
    if (lpTrack) {
        //LOGV("deleting lpTrack: %x\n", (int)lpTrack);
        lpTrack->stop();
        delete lpTrack;
    }
   
    // delete the JNI data
    AudioTrackJniStorage* pJniStorage = (AudioTrackJniStorage *)env->GetIntField(
        thiz, javaAudioTrackFields.jniData);
    if (pJniStorage) {
        // delete global refs created in native_setup
        env->DeleteGlobalRef(pJniStorage->mCallbackData.audioTrack_class);
        env->DeleteGlobalRef(pJniStorage->mCallbackData.audioTrack_ref);
        //LOGV("deleting pJniStorage: %x\n", (int)pJniStorage);
        delete pJniStorage;
    }
}
-----------------------------android_media_AudioTrack_native_finalize-----------------------------------
    // + reset the native resources in the Java object so any attempt to access
    // them after a call to release fails.
    env->SetIntField(thiz, javaAudioTrackFields.nativeTrackInJavaObj, 0);
    env->SetIntField(thiz, javaAudioTrackFields.jniData, 0);
}
-----------------------------android_media_AudioTrack_native_release-----------------------------------
        mState = STATE_UNINITIALIZED;
    }
------------------------------release----------------------------------
    }
###########################################################

&&&&&&&&&&&&&&&&&&&&&&&總結&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
pause與stop類似，都會調用函數AudioSystem::stopOutput。
差別是，stop會reset，也就是將audio_track_cblk_t中的user, server等清0。
而pause不會。

這也就是在播放的時候，按暫停，播放進度條會停在當前位置不動，按停止的話，進度條則回到了初始狀態。
&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&

 

 

摘自：江風的專欄