When Running in MediaCodec Mode, Widevine Freezes If You Rewind

There was a subtle interaction between Widevine's libraries and MediaCodec
mode.  Widevine's code assumed (erroneously) that video seeks would always
happen before audio seeks, and because we can't seek audio and video
independently from each other, we would ignore audio seeks but respect video
seeks.  This led to a problem since MediaCodec mode calls seeks in arbitrary
order.

Fix is to always respect the first request we get to seek and ignore the
second.

Bug: 6793514
Change-Id: Ic9ec60e0e0f606c7a0de6283dd4c30318eebdbad

proprietary/wvm/WVMMediaSource.cpp

@@ -2,6 +2,7 @@
  * Copyright (C) 2011 Google, Inc.  All Rights Reserved
  */
 
+//#define LOG_NDEBUG 0
 #define LOG_TAG "WVMMediaSource"
 #include <utils/Log.h>
 
@@ -24,6 +25,7 @@ static void _cb(int code)
 }
 
 status_t WVMMediaSource::sLastError = NO_ERROR;
+int64_t WVMMediaSource::mLastSeekTimeUs = -1;
 
 WVMMediaSource::WVMMediaSource(WVSession *session, WVEsSelector esSelector,
                                const sp<MetaData> &metaData, bool isLive,
@@ -246,8 +248,10 @@ status_t WVMMediaSource::read(MediaBuffer **buffer, const ReadOptions *options)
             // prior to the specified time.
             seekNextSync = true;
         } else {
-            // Let video stream control seek
-            if (mESSelector == WV_EsSelector_Video) {
+            // Whichever stream gets the seek first should do the actual seeking.
+            // To keep from double-seeking, we share the information about who
+            // has seeked most recently.
+            if (mLastSeekTimeUs != seekTimeUs) {
                 float scaleUsed;
                 std::string when = usecToNPT(seekTimeUs) + std::string("-");
                 WVStatus result = WV_Play(mSession, 1.0, &scaleUsed, when );
@@ -255,6 +259,11 @@ status_t WVMMediaSource::read(MediaBuffer **buffer, const ReadOptions *options)
                     ALOGE("WV_Play returned status %d in WVMMediaSource::read\n", result);
                     return ERROR_IO;
                 }
+                mLastSeekTimeUs = seekTimeUs;
+            } else {
+                // Now that both video and audio were seeked, clear the shared
+                // data.
+                mLastSeekTimeUs = -1;
             }
         }
     }

proprietary/wvm/include/WVMMediaSource.h

@@ -69,17 +69,16 @@ public:
         memcpy(mCryptoPluginKey, key, sizeof(mCryptoPluginKey));
     }
 
-private:
-    DecryptContext mDecryptContext;
-
 protected:
     virtual ~WVMMediaSource();
 
 private:
+    static int64_t mLastSeekTimeUs;
     Mutex mLock;
 
     WVSession *mSession;
     WVEsSelector mESSelector;  // indicates audio vs. video
+    DecryptContext mDecryptContext;
 
     sp<MetaData> mTrackMetaData;
 
@@ -94,6 +93,7 @@ private:
     MediaBufferGroup *mGroup;
 
     int64_t mKeyTime;
+
     unsigned long long mDts;
     unsigned long long mPts;