[audio][nuplayer] Aggregate buffers to reduce power.

Combine audio data from multiple buffers into one.
This reduces churn between threads and saves battery power.

Only use buffer aggregation when offloading the decoder.
Pend buffer if it won't fit in the bigger buffer.

Bug: 15094301
Change-Id: Iad3dac90b5d6b0fa43432b0e6776652ee2eafaa1
Signed-off-by: Phil Burk <philburk@google.com>

2 files changed, 94 insertions, 4 deletions

diff --git a/media/libmediaplayerservice/nuplayer/NuPlayer.cpp b/media/libmediaplayerservice/nuplayer/NuPlayer.cpp
index 76d25de..2bffed1 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayer.cpp
+++ b/media/libmediaplayerservice/nuplayer/NuPlayer.cpp
@@ -984,6 +984,8 @@ void NuPlayer::finishFlushIfPossible() {
 
     ALOGV("both audio and video are flushed now.");
 
+    mPendingAudioAccessUnit.clear();
+
     if (mTimeDiscontinuityPending) {
         mRenderer->signalTimeDiscontinuity();
         mTimeDiscontinuityPending = false;
@@ -1240,14 +1242,48 @@ status_t NuPlayer::feedDecoderInputData(bool audio, const sp<AMessage> &msg) {
 
     sp<ABuffer> accessUnit;
 
+    // Aggregate smaller buffers into a larger buffer.
+    // The goal is to reduce power consumption.
+    // Unfortunately this does not work with the software AAC decoder.
+    // TODO optimize buffer size for power consumption
+    // The offload read buffer size is 32 KB but 24 KB uses less power.
+    const int kAudioBigBufferSizeBytes = 24 * 1024;
+    bool doBufferAggregation = (audio && mOffloadAudio);
+    sp<ABuffer> biggerBuffer;
+    bool needMoreData = false;
+    int numSmallBuffers = 0;
+    bool gotTime = false;
+
     bool dropAccessUnit;
     do {
-        status_t err = mSource->dequeueAccessUnit(audio, &accessUnit);
+        status_t err;
+        // Did we save an accessUnit earlier because of a discontinuity?
+        if (audio && (mPendingAudioAccessUnit != NULL)) {
+            accessUnit = mPendingAudioAccessUnit;
+            mPendingAudioAccessUnit.clear();
+            err = mPendingAudioErr;
+            ALOGV("feedDecoderInputData() use mPendingAudioAccessUnit");
+        } else {
+            err = mSource->dequeueAccessUnit(audio, &accessUnit);
+        }
 
         if (err == -EWOULDBLOCK) {
-            return err;
+            ALOGD("feedDecoderInputData() got EWOULDBLOCK");
+            if (biggerBuffer == NULL) {
+                return err;
+            } else {
+                break; // Reply with data that we already have.
+            }
         } else if (err != OK) {
             if (err == INFO_DISCONTINUITY) {
+                if (biggerBuffer != NULL) {
+                    // We already have some data so save this for later.
+                    mPendingAudioErr = err;
+                    mPendingAudioAccessUnit = accessUnit;
+                    accessUnit.clear();
+                    ALOGD("feedDecoderInputData() save discontinuity for later");
+                    break;
+                }
                 int32_t type;
                 CHECK(accessUnit->meta()->findInt32("discontinuity", &type));
 
@@ -1352,7 +1388,52 @@ status_t NuPlayer::feedDecoderInputData(bool audio, const sp<AMessage> &msg) {
             dropAccessUnit = true;
             ++mNumFramesDropped;
         }
-    } while (dropAccessUnit);
+
+        size_t smallSize = accessUnit->size();
+        needMoreData = false;
+        if (doBufferAggregation && (biggerBuffer == NULL)
+                // Don't bother if only room for a few small buffers.
+                && (smallSize < (kAudioBigBufferSizeBytes / 3))) {
+            // Create a larger buffer for combining smaller buffers from the extractor.
+            biggerBuffer = new ABuffer(kAudioBigBufferSizeBytes);
+            biggerBuffer->setRange(0, 0); // start empty
+        }
+
+        if (biggerBuffer != NULL) {
+            int64_t timeUs;
+            bool smallTimestampValid = accessUnit->meta()->findInt64("timeUs", &timeUs);
+            // Will the smaller buffer fit?
+            size_t bigSize = biggerBuffer->size();
+            size_t roomLeft = biggerBuffer->capacity() - bigSize;
+            // Should we save this small buffer for the next big buffer?
+            // If the first small buffer did not have a timestamp then save
+            // any buffer that does have a timestamp until the next big buffer.
+            if ((smallSize > roomLeft)
+                || (!gotTime && (numSmallBuffers > 0) && smallTimestampValid)) {
+                mPendingAudioErr = err;
+                mPendingAudioAccessUnit = accessUnit;
+                accessUnit.clear();
+            } else {
+                // Append small buffer to the bigger buffer.
+                memcpy(biggerBuffer->base() + bigSize, accessUnit->data(), smallSize);
+                bigSize += smallSize;
+                biggerBuffer->setRange(0, bigSize);
+
+                // Keep looping until we run out of room in the biggerBuffer.
+                needMoreData = true;
+
+                // Grab time from first small buffer if available.
+                if ((numSmallBuffers == 0) && smallTimestampValid) {
+                    biggerBuffer->meta()->setInt64("timeUs", timeUs);
+                    gotTime = true;
+                }
+
+                ALOGV("feedDecoderInputData() #%d, smallSize = %zu, bigSize = %zu, capacity = %zu",
+                        numSmallBuffers, smallSize, bigSize, biggerBuffer->capacity());
+                numSmallBuffers++;
+            }
+        }
+    } while (dropAccessUnit || needMoreData);
 
     // ALOGV("returned a valid buffer of %s data", audio ? "audio" : "video");
 
@@ -1368,7 +1449,13 @@ status_t NuPlayer::feedDecoderInputData(bool audio, const sp<AMessage> &msg) {
         mCCDecoder->decode(accessUnit);
     }
 
-    reply->setBuffer("buffer", accessUnit);
+    if (biggerBuffer != NULL) {
+        ALOGV("feedDecoderInputData() reply with aggregated buffer, %d", numSmallBuffers);
+        reply->setBuffer("buffer", biggerBuffer);
+    } else {
+        reply->setBuffer("buffer", accessUnit);
+    }
+
     reply->post();
 
     return OK;
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayer.h b/media/libmediaplayerservice/nuplayer/NuPlayer.h
index 511d752..b318cfe 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayer.h
+++ b/media/libmediaplayerservice/nuplayer/NuPlayer.h
@@ -157,6 +157,9 @@ private:
     // notion of time has changed.
     bool mTimeDiscontinuityPending;
 
+    sp<ABuffer> mPendingAudioAccessUnit;
+    status_t    mPendingAudioErr;
+
     FlushStatus mFlushingAudio;
     FlushStatus mFlushingVideo;