diff --git a/media/libmediaplayerservice/nuplayer/GenericSource.cpp b/media/libmediaplayerservice/nuplayer/GenericSource.cpp
index b3efd74..5406825 100644
--- a/media/libmediaplayerservice/nuplayer/GenericSource.cpp
+++ b/media/libmediaplayerservice/nuplayer/GenericSource.cpp
@@ -168,6 +168,9 @@
 
     for (size_t i = 0; i < numtracks; ++i) {
         sp<MediaSource> track = extractor->getTrack(i);
+        if (track == NULL) {
+            continue;
+        }
 
         sp<MetaData> meta = extractor->getTrackMetaData(i);
 
@@ -210,22 +213,25 @@
             }
         }
 
-        if (track != NULL) {
-            mSources.push(track);
-            int64_t durationUs;
-            if (meta->findInt64(kKeyDuration, &durationUs)) {
-                if (durationUs > mDurationUs) {
-                    mDurationUs = durationUs;
-                }
-            }
-
-            int32_t bitrate;
-            if (totalBitrate >= 0 && meta->findInt32(kKeyBitRate, &bitrate)) {
-                totalBitrate += bitrate;
-            } else {
-                totalBitrate = -1;
+        mSources.push(track);
+        int64_t durationUs;
+        if (meta->findInt64(kKeyDuration, &durationUs)) {
+            if (durationUs > mDurationUs) {
+                mDurationUs = durationUs;
             }
         }
+
+        int32_t bitrate;
+        if (totalBitrate >= 0 && meta->findInt32(kKeyBitRate, &bitrate)) {
+            totalBitrate += bitrate;
+        } else {
+            totalBitrate = -1;
+        }
+    }
+
+    if (mSources.size() == 0) {
+        ALOGE("b/23705695");
+        return UNKNOWN_ERROR;
     }
 
     mBitrate = totalBitrate;
@@ -257,7 +263,7 @@
 
 status_t NuPlayer::GenericSource::setBuffers(
         bool audio, Vector<MediaBuffer *> &buffers) {
-    if (mIsWidevine && !audio) {
+    if (mIsWidevine && !audio && mVideoTrack.mSource != NULL) {
         return mVideoTrack.mSource->setBuffers(buffers);
     }
     return INVALID_OPERATION;
diff --git a/media/libstagefright/MPEG4Extractor.cpp b/media/libstagefright/MPEG4Extractor.cpp
index a5b28e6..38754e8 100644
--- a/media/libstagefright/MPEG4Extractor.cpp
+++ b/media/libstagefright/MPEG4Extractor.cpp
@@ -923,6 +923,11 @@
             }
 
             if (isTrack) {
+                int32_t trackId;
+                // There must be exact one track header per track.
+                if (!mLastTrack->meta->findInt32(kKeyTrackID, &trackId)) {
+                    mLastTrack->skipTrack = true;
+                }
                 if (mLastTrack->skipTrack) {
                     Track *cur = mFirstTrack;
 
@@ -2651,6 +2656,9 @@
                 break;
             }
         }
+    } else {
+        ALOGE("b/21657957");
+        return NULL;
     }
 
     ALOGV("getTrack called, pssh: %zu", mPssh.size());
diff --git a/media/libstagefright/SampleIterator.cpp b/media/libstagefright/SampleIterator.cpp
index 2748349..c5f359e 100644
--- a/media/libstagefright/SampleIterator.cpp
+++ b/media/libstagefright/SampleIterator.cpp
@@ -84,6 +84,11 @@
 
     CHECK(sampleIndex < mStopChunkSampleIndex);
 
+    if (mSamplesPerChunk == 0) {
+        ALOGE("b/22802344");
+        return ERROR_MALFORMED;
+    }
+
     uint32_t chunk =
         (sampleIndex - mFirstChunkSampleIndex) / mSamplesPerChunk
         + mFirstChunk;