AudioRecord: Add retrograde detection to timestamps

Test: atest AudioRecordTest
Test: camera record stop/start with debug log
Bug: 147198344
Change-Id: Idd7a0bbd1938073b7b7751595b15e20e54ea3373

media/libaudioclient/AudioRecord.cpp

@@ -411,6 +411,9 @@ status_t AudioRecord::start(AudioSystem::sync_event_t event, audio_session_t tri
     mFramesReadServerOffset -= mFramesRead + framesFlushed;
     mFramesRead = 0;
     mProxy->clearTimestamp();  // timestamp is invalid until next server push
+    mPreviousTimestamp.clear();
+    mTimestampRetrogradePositionReported = false;
+    mTimestampRetrogradeTimeReported = false;
 
     // reset current position as seen by client to 0
     mProxy->setEpoch(mProxy->getEpoch() - mProxy->getPosition());
@@ -600,6 +603,39 @@ status_t AudioRecord::getTimestamp(ExtendedTimestamp *timestamp)
                 timestamp->mPosition[i] += mFramesReadServerOffset;
             }
         }
+
+        bool timestampRetrogradeTimeReported = false;
+        bool timestampRetrogradePositionReported = false;
+        for (int i = 0; i < ExtendedTimestamp::LOCATION_MAX; ++i) {
+            if (timestamp->mTimeNs[i] >= 0 && mPreviousTimestamp.mTimeNs[i] >= 0) {
+                if (timestamp->mTimeNs[i] < mPreviousTimestamp.mTimeNs[i]) {
+                    if (!mTimestampRetrogradeTimeReported) {
+                        ALOGD("%s: retrograde time adjusting [%d] current:%lld to previous:%lld",
+                                __func__, i, (long long)timestamp->mTimeNs[i],
+                                (long long)mPreviousTimestamp.mTimeNs[i]);
+                        timestampRetrogradeTimeReported = true;
+                    }
+                    timestamp->mTimeNs[i] = mPreviousTimestamp.mTimeNs[i];
+                }
+                if (timestamp->mPosition[i] < mPreviousTimestamp.mPosition[i]) {
+                    if (!mTimestampRetrogradePositionReported) {
+                        ALOGD("%s: retrograde position"
+                                " adjusting [%d] current:%lld to previous:%lld",
+                                __func__, i, (long long)timestamp->mPosition[i],
+                                (long long)mPreviousTimestamp.mPosition[i]);
+                        timestampRetrogradePositionReported = true;
+                    }
+                    timestamp->mPosition[i] = mPreviousTimestamp.mPosition[i];
+                }
+            }
+        }
+        mPreviousTimestamp = *timestamp;
+        if (timestampRetrogradeTimeReported) {
+            mTimestampRetrogradeTimeReported = true;
+        }
+        if (timestampRetrogradePositionReported) {
+            mTimestampRetrogradePositionReported = true;
+        }
     }
     return status;
 }

media/libaudioclient/include/media/AudioRecord.h

@@ -711,6 +711,10 @@ private:
 
     bool                    mInOverrun;         // whether recorder is currently in overrun state
 
+    ExtendedTimestamp       mPreviousTimestamp{}; // used to detect retrograde motion
+    bool                    mTimestampRetrogradePositionReported = false; // reduce log spam
+    bool                    mTimestampRetrogradeTimeReported = false;     // reduce log spam
+
 private:
     class DeathNotifier : public IBinder::DeathRecipient {
     public: