commit b01faa31462e19957ae3c0c3ada07c9576a9494f
author Andy Hung <hunga@google.com> Wed Apr 27 12:51:32 2016 -0700
committer Andy Hung <hunga@google.com> Fri Apr 29 18:16:03 2016 -0700
tree 8e01ae4c10bb12e81745787526c34ba3b6abf2af
parent ecd0a41d9a2cc9efbc4ad6d4c91d417461772933

AudioTrack: Fix timestamp jitter

When HAL out_get_presentation_position returns error,
use server position adjusted for latency.

Bug: 28250436
Change-Id: I3dbcb9b7c4e56d34e7e161d1a02d8f64afd602b9

include/media/AudioTimestamp.h

diff --git a/include/media/AudioTimestamp.h b/include/media/AudioTimestamp.h
index 969003c..4f504a4 100644
--- a/include/media/AudioTimestamp.h
+++ b/include/media/AudioTimestamp.h
@@ -36,6 +36,7 @@
 
 struct ExtendedTimestamp {
     enum Location {
+        LOCATION_INVALID = -1,
         LOCATION_CLIENT,   // timestamp of last read frame from client-server track buffer
         LOCATION_SERVER,   // timestamp of newest frame from client-server track buffer
         LOCATION_KERNEL,   // timestamp of newest frame in the kernel (alsa) buffer.
@@ -89,8 +90,10 @@
     }
 
     // Returns the best timestamp as judged from the closest-to-hw stage in the
-    // pipeline with a valid timestamp.
-    status_t getBestTimestamp(int64_t *position, int64_t *time, int timebase) const {
+    // pipeline with a valid timestamp.  If the optional location parameter is non-null,
+    // it will be filled with the location where the time was obtained.
+    status_t getBestTimestamp(
+            int64_t *position, int64_t *time, int timebase, Location *location = nullptr) const {
         if (position == nullptr || time == nullptr
                 || timebase < 0 || timebase >= TIMEBASE_MAX) {
             return BAD_VALUE;
@@ -102,18 +105,21 @@
             if (mTimeNs[i] > 0) {
                 *position = mPosition[i];
                 *time = mTimeNs[i] + mTimebaseOffset[timebase];
+                if (location != nullptr) {
+                    *location = (Location)i;
+                }
                 return OK;
             }
         }
         return INVALID_OPERATION;
     }
 
-    status_t getBestTimestamp(AudioTimestamp *timestamp) const {
+    status_t getBestTimestamp(AudioTimestamp *timestamp, Location *location = nullptr) const {
         if (timestamp == nullptr) {
             return BAD_VALUE;
         }
         int64_t position, time;
-        if (getBestTimestamp(&position, &time, TIMEBASE_MONOTONIC) == OK) {
+        if (getBestTimestamp(&position, &time, TIMEBASE_MONOTONIC, location) == OK) {
             timestamp->mPosition = position;
             timestamp->mTime.tv_sec = time / 1000000000;
             timestamp->mTime.tv_nsec = time - timestamp->mTime.tv_sec * 1000000000LL;

include/media/AudioTrack.h

diff --git a/include/media/AudioTrack.h b/include/media/AudioTrack.h
index fc7217a..3cadf6b 100644
--- a/include/media/AudioTrack.h
+++ b/include/media/AudioTrack.h
@@ -1024,6 +1024,8 @@
     bool                    mTimestampStartupGlitchReported; // reduce log spam
     bool                    mRetrogradeMotionReported; // reduce log spam
     AudioTimestamp          mPreviousTimestamp;     // used to detect retrograde motion
+    ExtendedTimestamp::Location mPreviousLocation;  // location used for previous timestamp
+    double                  mComputedLatencyMs;     // latency between server and kernel
 
     uint32_t                mUnderrunCountOffset;   // updated when restoring tracks