DO NOT MERGE: Make sure we restart the prefetcher immediately when trying to satisfy a read.

Change-Id: I27c2b5d20ae577e71936d32522f70f6ba08cc247
related-to-bug: 4286618

media/libstagefright/AwesomePlayer.cpp

@@ -1127,7 +1127,7 @@ void AwesomePlayer::finishSeekIfNecessary(int64_t videoTimeUs) {
     }
 
     if (mAudioPlayer != NULL) {
-        LOGV("seeking audio to %lld us (%.2f secs).", timeUs, timeUs / 1E6);
+        LOGV("seeking audio to %lld us (%.2f secs).", videoTimeUs, videoTimeUs / 1E6);
 
         // If we don't have a video time, seek audio to the originally
         // requested seek time instead.

media/libstagefright/NuCachedSource2.cpp

@@ -326,24 +326,31 @@ void NuCachedSource2::onRead(const sp<AMessage> &msg) {
     mCondition.signal();
 }
 
-void NuCachedSource2::restartPrefetcherIfNecessary_l() {
+void NuCachedSource2::restartPrefetcherIfNecessary_l(bool force) {
     static const size_t kGrayArea = 256 * 1024;
 
     if (mFetching || mFinalStatus != OK) {
         return;
     }
 
-    if (mCacheOffset + mCache->totalSize() - mLastAccessPos
-            >= kLowWaterThreshold) {
-        return;
-    }
+    size_t maxBytes;
 
-    size_t maxBytes = mLastAccessPos - mCacheOffset;
-    if (maxBytes < kGrayArea) {
-        return;
-    }
+    if (!force) {
+        if (mCacheOffset + mCache->totalSize() - mLastAccessPos
+                >= kLowWaterThreshold) {
+            return;
+        }
 
-    maxBytes -= kGrayArea;
+        maxBytes = mLastAccessPos - mCacheOffset;
+        if (maxBytes < kGrayArea) {
+            return;
+        }
+
+        maxBytes -= kGrayArea;
+    } else {
+        // Empty it all out.
+        maxBytes = mLastAccessPos - mCacheOffset;
+    }
 
     size_t actualBytes = mCache->releaseFromStart(maxBytes);
     mCacheOffset += actualBytes;
@@ -415,10 +422,17 @@ size_t NuCachedSource2::approxDataRemaining_l(bool *eos) {
 }
 
 ssize_t NuCachedSource2::readInternal(off_t offset, void *data, size_t size) {
+    CHECK(size <= kHighWaterThreshold);
+
     LOGV("readInternal offset %ld size %d", offset, size);
 
     Mutex::Autolock autoLock(mLock);
 
+    if (!mFetching) {
+        mLastAccessPos = offset;
+        restartPrefetcherIfNecessary_l(true /* force */);
+    }
+
     if (offset < mCacheOffset
             || offset >= (off_t)(mCacheOffset + mCache->totalSize())) {
         static const off_t kPadding = 32768;

media/libstagefright/include/NuCachedSource2.h

@@ -94,7 +94,7 @@ private:
     status_t seekInternal_l(off_t offset);
 
     size_t approxDataRemaining_l(bool *eos);
-    void restartPrefetcherIfNecessary_l();
+    void restartPrefetcherIfNecessary_l(bool force = false);
 
     DISALLOW_EVIL_CONSTRUCTORS(NuCachedSource2);
 };