libmediaplayerservice: offload playback support

Main change is to how recycled tracks are used for gapless
playback. If we are playing offloaded tracks that can't be
recycled we don't open a new offloaded output until we have
closed the previous one. This is because offloaded tracks
are a limited resource so we don't want to spuriously create
unnecessary instances. If the tracks cannot be recycled
this means that the formats are incompatible and so the
hardware most likely will also be unable to use the existing
output channel for the new track. If we already have the
maximum number of hardware offload channels open (which could
be only one) then creation of the next output would fail if
we attempted it while the previous output was still open.

Change-Id: I4f5958074e7ffd2e17108157fee86329506730ea
Signed-off-by: Eric Laurent <elaurent@google.com>

2 files changed, 207 insertions, 84 deletions

diff --git a/media/libmediaplayerservice/MediaPlayerService.cpp b/media/libmediaplayerservice/MediaPlayerService.cpp
index afde373..8833bd7 100644
--- a/media/libmediaplayerservice/MediaPlayerService.cpp
+++ b/media/libmediaplayerservice/MediaPlayerService.cpp
@@ -53,6 +53,8 @@
 #include <media/AudioTrack.h>
 #include <media/MemoryLeakTrackUtil.h>
 #include <media/stagefright/MediaErrors.h>
+#include <media/stagefright/AudioPlayer.h>
+#include <media/stagefright/foundation/ADebug.h>
 
 #include <system/audio.h>
 
@@ -1381,6 +1383,45 @@ status_t MediaPlayerService::AudioOutput::getFramesWritten(uint32_t *frameswritt
     return OK;
 }
 
+status_t MediaPlayerService::AudioOutput::setParameters(const String8& keyValuePairs)
+{
+    if (mTrack == 0) return NO_INIT;
+    return mTrack->setParameters(keyValuePairs);
+}
+
+String8  MediaPlayerService::AudioOutput::getParameters(const String8& keys)
+{
+    if (mTrack == 0) return String8::empty();
+    return mTrack->getParameters(keys);
+}
+
+void MediaPlayerService::AudioOutput::deleteRecycledTrack()
+{
+    ALOGV("deleteRecycledTrack");
+
+    if (mRecycledTrack != 0) {
+
+        if (mCallbackData != NULL) {
+            mCallbackData->setOutput(NULL);
+            mCallbackData->endTrackSwitch();
+        }
+
+        if ((mRecycledTrack->getFlags() & AUDIO_OUTPUT_FLAG_COMPRESS_OFFLOAD) == 0) {
+            mRecycledTrack->flush();
+        }
+        // An offloaded track isn't flushed because the STREAM_END is reported
+        // slightly prematurely to allow time for the gapless track switch
+        // but this means that if we decide not to recycle the track there
+        // could be a small amount of residual data still playing. We leave
+        // AudioFlinger to drain the track.
+
+        mRecycledTrack.clear();
+        delete mCallbackData;
+        mCallbackData = NULL;
+        close();
+    }
+}
+
 status_t MediaPlayerService::AudioOutput::open(
         uint32_t sampleRate, int channelCount, audio_channel_mask_t channelMask,
         audio_format_t format, int bufferCount,
@@ -1397,20 +1438,34 @@ status_t MediaPlayerService::AudioOutput::open(
         bufferCount = mMinBufferCount;
 
     }
-    ALOGV("open(%u, %d, 0x%x, %d, %d, %d)", sampleRate, channelCount, channelMask,
-            format, bufferCount, mSessionId);
+    ALOGV("open(%u, %d, 0x%x, 0x%x, %d, %d 0x%x)", sampleRate, channelCount, channelMask,
+                format, bufferCount, mSessionId, flags);
     uint32_t afSampleRate;
     size_t afFrameCount;
     uint32_t frameCount;
 
-    if (AudioSystem::getOutputFrameCount(&afFrameCount, mStreamType) != NO_ERROR) {
-        return NO_INIT;
-    }
-    if (AudioSystem::getOutputSamplingRate(&afSampleRate, mStreamType) != NO_ERROR) {
-        return NO_INIT;
+    // offloading is only supported in callback mode for now.
+    // offloadInfo must be present if offload flag is set
+    if (((flags & AUDIO_OUTPUT_FLAG_COMPRESS_OFFLOAD) != 0) &&
+            ((cb == NULL) || (offloadInfo == NULL))) {
+        return BAD_VALUE;
     }
 
-    frameCount = (sampleRate*afFrameCount*bufferCount)/afSampleRate;
+    if ((flags & AUDIO_OUTPUT_FLAG_COMPRESS_OFFLOAD) != 0) {
+        frameCount = 0; // AudioTrack will get frame count from AudioFlinger
+    } else {
+        uint32_t afSampleRate;
+        size_t afFrameCount;
+
+        if (AudioSystem::getOutputFrameCount(&afFrameCount, mStreamType) != NO_ERROR) {
+            return NO_INIT;
+        }
+        if (AudioSystem::getOutputSamplingRate(&afSampleRate, mStreamType) != NO_ERROR) {
+            return NO_INIT;
+        }
+
+        frameCount = (sampleRate*afFrameCount*bufferCount)/afSampleRate;
+    }
 
     if (channelMask == CHANNEL_MASK_USE_CHANNEL_ORDER) {
         channelMask = audio_channel_out_mask_from_count(channelCount);
@@ -1420,65 +1475,108 @@ status_t MediaPlayerService::AudioOutput::open(
         }
     }
 
-    sp<AudioTrack> t;
-    CallbackData *newcbd = NULL;
-    if (mCallback != NULL) {
-        newcbd = new CallbackData(this);
-        t = new AudioTrack(
-                mStreamType,
-                sampleRate,
-                format,
-                channelMask,
-                frameCount,
-                flags,
-                CallbackWrapper,
-                newcbd,
-                0,  // notification frames
-                mSessionId);
-    } else {
-        t = new AudioTrack(
-                mStreamType,
-                sampleRate,
-                format,
-                channelMask,
-                frameCount,
-                flags,
-                NULL,
-                NULL,
-                0,
-                mSessionId);
-    }
-
-    if ((t == 0) || (t->initCheck() != NO_ERROR)) {
-        ALOGE("Unable to create audio track");
-        delete newcbd;
-        return NO_INIT;
-    }
-
+    // Check whether we can recycle the track
+    bool reuse = false;
+    bool bothOffloaded = false;
 
     if (mRecycledTrack != 0) {
+        // check whether we are switching between two offloaded tracks
+        bothOffloaded = (flags & mRecycledTrack->getFlags()
+                                & AUDIO_OUTPUT_FLAG_COMPRESS_OFFLOAD) != 0;
+
         // check if the existing track can be reused as-is, or if a new track needs to be created.
+        reuse = true;
 
-        bool reuse = true;
         if ((mCallbackData == NULL && mCallback != NULL) ||
                 (mCallbackData != NULL && mCallback == NULL)) {
             // recycled track uses callbacks but the caller wants to use writes, or vice versa
             ALOGV("can't chain callback and write");
             reuse = false;
         } else if ((mRecycledTrack->getSampleRate() != sampleRate) ||
-                (mRecycledTrack->channelCount() != channelCount) ||
-                (mRecycledTrack->frameCount() != t->frameCount())) {
-            ALOGV("samplerate, channelcount or framecount differ: %d/%d Hz, %d/%d ch, %d/%d frames",
+                (mRecycledTrack->channelCount() != (uint32_t)channelCount) ) {
+            ALOGV("samplerate, channelcount differ: %u/%u Hz, %u/%d ch",
                   mRecycledTrack->getSampleRate(), sampleRate,
-                  mRecycledTrack->channelCount(), channelCount,
-                  mRecycledTrack->frameCount(), t->frameCount());
+                  mRecycledTrack->channelCount(), channelCount);
             reuse = false;
         } else if (flags != mFlags) {
             ALOGV("output flags differ %08x/%08x", flags, mFlags);
             reuse = false;
+        } else if (mRecycledTrack->format() != format) {
+            reuse = false;
+        }
+    } else {
+        ALOGV("no track available to recycle");
+    }
+
+    ALOGV_IF(bothOffloaded, "both tracks offloaded");
+
+    // If we can't recycle and both tracks are offloaded
+    // we must close the previous output before opening a new one
+    if (bothOffloaded && !reuse) {
+        ALOGV("both offloaded and not recycling");
+        deleteRecycledTrack();
+    }
+
+    sp<AudioTrack> t;
+    CallbackData *newcbd = NULL;
+
+    // We don't attempt to create a new track if we are recycling an
+    // offloaded track. But, if we are recycling a non-offloaded or we
+    // are switching where one is offloaded and one isn't then we create
+    // the new track in advance so that we can read additional stream info
+
+    if (!(reuse && bothOffloaded)) {
+        ALOGV("creating new AudioTrack");
+
+        if (mCallback != NULL) {
+            newcbd = new CallbackData(this);
+            t = new AudioTrack(
+                    mStreamType,
+                    sampleRate,
+                    format,
+                    channelMask,
+                    frameCount,
+                    flags,
+                    CallbackWrapper,
+                    newcbd,
+                    0,  // notification frames
+                    mSessionId,
+                    AudioTrack::TRANSFER_CALLBACK,
+                    offloadInfo);
+        } else {
+            t = new AudioTrack(
+                    mStreamType,
+                    sampleRate,
+                    format,
+                    channelMask,
+                    frameCount,
+                    flags,
+                    NULL,
+                    NULL,
+                    0,
+                    mSessionId);
+        }
+
+        if ((t == 0) || (t->initCheck() != NO_ERROR)) {
+            ALOGE("Unable to create audio track");
+            delete newcbd;
+            return NO_INIT;
+        }
+    }
+
+    if (reuse) {
+        CHECK(mRecycledTrack != NULL);
+
+        if (!bothOffloaded) {
+            if (mRecycledTrack->frameCount() != t->frameCount()) {
+                ALOGV("framecount differs: %u/%u frames",
+                      mRecycledTrack->frameCount(), t->frameCount());
+                reuse = false;
+            }
         }
+
         if (reuse) {
-            ALOGV("chaining to next output");
+            ALOGV("chaining to next output and recycling track");
             close();
             mTrack = mRecycledTrack;
             mRecycledTrack.clear();
@@ -1488,19 +1586,16 @@ status_t MediaPlayerService::AudioOutput::open(
             delete newcbd;
             return OK;
         }
+    }
 
-        // if we're not going to reuse the track, unblock and flush it
-        if (mCallbackData != NULL) {
-            mCallbackData->setOutput(NULL);
-            mCallbackData->endTrackSwitch();
-        }
-        mRecycledTrack->flush();
-        mRecycledTrack.clear();
-        delete mCallbackData;
-        mCallbackData = NULL;
-        close();
+    // we're not going to reuse the track, unblock and flush it
+    // this was done earlier if both tracks are offloaded
+    if (!bothOffloaded) {
+        deleteRecycledTrack();
     }
 
+    CHECK((t != NULL) && ((mCallback == NULL) || (newcbd != NULL)));
+
     mCallbackData = newcbd;
     ALOGV("setVolume");
     t->setVolume(mLeftVolume, mRightVolume);
@@ -1514,15 +1609,19 @@ status_t MediaPlayerService::AudioOutput::open(
     }
     mTrack = t;
 
-    status_t res = t->setSampleRate(mPlaybackRatePermille * mSampleRateHz / 1000);
-    if (res != NO_ERROR) {
-        return res;
+    status_t res = NO_ERROR;
+    if ((flags & AUDIO_OUTPUT_FLAG_COMPRESS_OFFLOAD) == 0) {
+        res = t->setSampleRate(mPlaybackRatePermille * mSampleRateHz / 1000);
+        if (res == NO_ERROR) {
+            t->setAuxEffectSendLevel(mSendLevel);
+            res = t->attachAuxEffect(mAuxEffectId);
+        }
     }
-    t->setAuxEffectSendLevel(mSendLevel);
-    return t->attachAuxEffect(mAuxEffectId);;
+    ALOGV("open() DONE status %d", res);
+    return res;
 }
 
-void MediaPlayerService::AudioOutput::start()
+status_t MediaPlayerService::AudioOutput::start()
 {
     ALOGV("start");
     if (mCallbackData != NULL) {
@@ -1531,8 +1630,9 @@ void MediaPlayerService::AudioOutput::start()
     if (mTrack != 0) {
         mTrack->setVolume(mLeftVolume, mRightVolume);
         mTrack->setAuxEffectSendLevel(mSendLevel);
-        mTrack->start();
+        return mTrack->start();
     }
+    return NO_INIT;
 }
 
 void MediaPlayerService::AudioOutput::setNextOutput(const sp<AudioOutput>& nextOutput) {
@@ -1645,10 +1745,6 @@ status_t MediaPlayerService::AudioOutput::attachAuxEffect(int effectId)
 void MediaPlayerService::AudioOutput::CallbackWrapper(
         int event, void *cookie, void *info) {
     //ALOGV("callbackwrapper");
-    if (event != AudioTrack::EVENT_MORE_DATA) {
-        return;
-    }
-
     CallbackData *data = (CallbackData*)cookie;
     data->lock();
     AudioOutput *me = data->getOutput();
@@ -1657,23 +1753,46 @@ void MediaPlayerService::AudioOutput::CallbackWrapper(
         // no output set, likely because the track was scheduled to be reused
         // by another player, but the format turned out to be incompatible.
         data->unlock();
-        buffer->size = 0;
+        if (buffer != NULL) {
+            buffer->size = 0;
+        }
         return;
     }
 
-    size_t actualSize = (*me->mCallback)(
-            me, buffer->raw, buffer->size, me->mCallbackCookie,
-            CB_EVENT_FILL_BUFFER);
+    switch(event) {
+    case AudioTrack::EVENT_MORE_DATA: {
+        size_t actualSize = (*me->mCallback)(
+                me, buffer->raw, buffer->size, me->mCallbackCookie,
+                CB_EVENT_FILL_BUFFER);
+
+        if (actualSize == 0 && buffer->size > 0 && me->mNextOutput == NULL) {
+            // We've reached EOS but the audio track is not stopped yet,
+            // keep playing silence.
+
+            memset(buffer->raw, 0, buffer->size);
+            actualSize = buffer->size;
+        }
+
+        buffer->size = actualSize;
+        } break;
 
-    if (actualSize == 0 && buffer->size > 0 && me->mNextOutput == NULL) {
-        // We've reached EOS but the audio track is not stopped yet,
-        // keep playing silence.
 
-        memset(buffer->raw, 0, buffer->size);
-        actualSize = buffer->size;
+    case AudioTrack::EVENT_STREAM_END:
+        ALOGV("callbackwrapper: deliver EVENT_STREAM_END");
+        (*me->mCallback)(me, NULL /* buffer */, 0 /* size */,
+                me->mCallbackCookie, CB_EVENT_STREAM_END);
+        break;
+
+    case AudioTrack::EVENT_NEW_IAUDIOTRACK :
+        ALOGV("callbackwrapper: deliver EVENT_TEAR_DOWN");
+        (*me->mCallback)(me,  NULL /* buffer */, 0 /* size */,
+                me->mCallbackCookie, CB_EVENT_TEAR_DOWN);
+        break;
+
+    default:
+        ALOGE("received unknown event type: %d inside CallbackWrapper !", event);
     }
 
-    buffer->size = actualSize;
     data->unlock();
 }
 
@@ -1803,10 +1922,11 @@ status_t MediaPlayerService::AudioCache::open(
     return NO_ERROR;
 }
 
-void MediaPlayerService::AudioCache::start() {
+status_t MediaPlayerService::AudioCache::start() {
     if (mCallbackThread != NULL) {
         mCallbackThread->run("AudioCache callback");
     }
+    return NO_ERROR;
 }
 
 void MediaPlayerService::AudioCache::stop() {
diff --git a/media/libmediaplayerservice/MediaPlayerService.h b/media/libmediaplayerservice/MediaPlayerService.h
index f7076cc..7d27944 100644
--- a/media/libmediaplayerservice/MediaPlayerService.h
+++ b/media/libmediaplayerservice/MediaPlayerService.h
@@ -94,7 +94,7 @@ class MediaPlayerService : public BnMediaPlayerService
                 audio_output_flags_t flags = AUDIO_OUTPUT_FLAG_NONE,
                 const audio_offload_info_t *offloadInfo = NULL);
 
-        virtual void            start();
+        virtual status_t        start();
         virtual ssize_t         write(const void* buffer, size_t size);
         virtual void            stop();
         virtual void            flush();
@@ -112,11 +112,14 @@ class MediaPlayerService : public BnMediaPlayerService
                 void            setNextOutput(const sp<AudioOutput>& nextOutput);
                 void            switchToNextOutput();
         virtual bool            needsTrailingPadding() { return mNextOutput == NULL; }
+        virtual status_t        setParameters(const String8& keyValuePairs);
+        virtual String8         getParameters(const String8& keys);
 
     private:
         static void             setMinBufferCount();
         static void             CallbackWrapper(
                 int event, void *me, void *info);
+               void             deleteRecycledTrack();
 
         sp<AudioTrack>          mTrack;
         sp<AudioTrack>          mRecycledTrack;
@@ -196,7 +199,7 @@ class MediaPlayerService : public BnMediaPlayerService
                 audio_output_flags_t flags = AUDIO_OUTPUT_FLAG_NONE,
                 const audio_offload_info_t *offloadInfo = NULL);
 
-        virtual void            start();
+        virtual status_t        start();
         virtual ssize_t         write(const void* buffer, size_t size);
         virtual void            stop();
         virtual void            flush() {}