Merge "aaudio: offset MMAP timestamps"

media/libaaudio/src/client/AudioStreamInternal.cpp

@@ -232,6 +232,24 @@ aaudio_result_t AudioStreamInternal::open(const AudioStreamBuilder &builder) {
         mCallbackBuffer = new uint8_t[callbackBufferSize];
     }
 
+    // For debugging and analyzing the distribution of MMAP timestamps.
+    // For OUTPUT, use a NEGATIVE offset to move the CPU writes further BEFORE the HW reads.
+    // For INPUT, use a POSITIVE offset to move the CPU reads further AFTER the HW writes.
+    // You can use this offset to reduce glitching.
+    // You can also use this offset to force glitching. By iterating over multiple
+    // values you can reveal the distribution of the hardware timing jitter.
+    if (mAudioEndpoint.isFreeRunning()) { // MMAP?
+        int32_t offsetMicros = (getDirection() == AAUDIO_DIRECTION_OUTPUT)
+                ? AAudioProperty_getOutputMMapOffsetMicros()
+                : AAudioProperty_getInputMMapOffsetMicros();
+        // This log is used to debug some tricky glitch issues. Please leave.
+        ALOGD_IF(offsetMicros, "%s() - %s mmap offset = %d micros",
+                __func__,
+                (getDirection() == AAUDIO_DIRECTION_OUTPUT) ? "output" : "input",
+                offsetMicros);
+        mTimeOffsetNanos = offsetMicros * AAUDIO_NANOS_PER_MICROSECOND;
+    }
+
     setState(AAUDIO_STREAM_STATE_OPEN);
 
     return result;
@@ -478,7 +496,8 @@ aaudio_result_t AudioStreamInternal::onTimestampService(AAudioServiceMessage *me
 #if LOG_TIMESTAMPS
     logTimestamp(*message);
 #endif
-    processTimestamp(message->timestamp.position, message->timestamp.timestamp);
+    processTimestamp(message->timestamp.position,
+            message->timestamp.timestamp + mTimeOffsetNanos);
     return AAUDIO_OK;
 }
 

media/libaaudio/src/client/AudioStreamInternal.h

@@ -194,6 +194,7 @@ private:
     // By delaying slightly we can avoid waking up before other side is ready.
     const int32_t            mWakeupDelayNanos; // delay past typical wakeup jitter
     const int32_t            mMinimumSleepNanos; // minimum sleep while polling
+    int32_t                  mTimeOffsetNanos = 0; // add to time part of an MMAP timestamp
 
     AudioEndpointParcelable  mEndPointParcelable; // description of the buffers filled by service
     EndpointDescriptor       mEndpointDescriptor; // buffer description with resolved addresses

media/libaaudio/src/utility/AAudioUtilities.cpp

@@ -335,6 +335,30 @@ int32_t AAudioProperty_getHardwareBurstMinMicros() {
     return prop;
 }
 
+static int32_t AAudioProperty_getMMapOffsetMicros(const char *functionName,
+        const char *propertyName) {
+    const int32_t minMicros = -20000; // arbitrary
+    const int32_t defaultMicros = 0;  // arbitrary
+    const int32_t maxMicros =  20000; // arbitrary
+    int32_t prop = property_get_int32(propertyName, defaultMicros);
+    if (prop < minMicros) {
+        ALOGW("%s: clipped %d to %d", functionName, prop, minMicros);
+        prop = minMicros;
+    } else if (prop > maxMicros) {
+        ALOGW("%s: clipped %d to %d", functionName, prop, minMicros);
+        prop = maxMicros;
+    }
+    return prop;
+}
+
+int32_t AAudioProperty_getInputMMapOffsetMicros() {
+    return AAudioProperty_getMMapOffsetMicros(__func__, AAUDIO_PROP_INPUT_MMAP_OFFSET_USEC);
+}
+
+int32_t AAudioProperty_getOutputMMapOffsetMicros() {
+    return AAudioProperty_getMMapOffsetMicros(__func__, AAUDIO_PROP_OUTPUT_MMAP_OFFSET_USEC);
+}
+
 aaudio_result_t AAudio_isFlushAllowed(aaudio_stream_state_t state) {
     aaudio_result_t result = AAUDIO_OK;
     switch (state) {

media/libaaudio/src/utility/AAudioUtilities.h

@@ -94,31 +94,26 @@ audio_flags_mask_t AAudioConvert_allowCapturePolicyToAudioFlagsMask(
 
 // Note that this code may be replaced by Settings or by some other system configuration tool.
 
-#define AAUDIO_PROP_MMAP_POLICY           "aaudio.mmap_policy"
-
 /**
  * Read system property.
  * @return AAUDIO_UNSPECIFIED, AAUDIO_POLICY_NEVER or AAUDIO_POLICY_AUTO or AAUDIO_POLICY_ALWAYS
  */
 int32_t AAudioProperty_getMMapPolicy();
-
-#define AAUDIO_PROP_MMAP_EXCLUSIVE_POLICY "aaudio.mmap_exclusive_policy"
+#define AAUDIO_PROP_MMAP_POLICY           "aaudio.mmap_policy"
 
 /**
  * Read system property.
  * @return AAUDIO_UNSPECIFIED, AAUDIO_POLICY_NEVER or AAUDIO_POLICY_AUTO or AAUDIO_POLICY_ALWAYS
  */
 int32_t AAudioProperty_getMMapExclusivePolicy();
-
-#define AAUDIO_PROP_MIXER_BURSTS           "aaudio.mixer_bursts"
+#define AAUDIO_PROP_MMAP_EXCLUSIVE_POLICY "aaudio.mmap_exclusive_policy"
 
 /**
  * Read system property.
  * @return number of bursts per AAudio service mixer cycle
  */
 int32_t AAudioProperty_getMixerBursts();
-
-#define AAUDIO_PROP_HW_BURST_MIN_USEC      "aaudio.hw_burst_min_usec"
+#define AAUDIO_PROP_MIXER_BURSTS           "aaudio.mixer_bursts"
 
 /**
  * Read a system property that specifies the number of extra microseconds that a thread
@@ -130,7 +125,6 @@ int32_t AAudioProperty_getMixerBursts();
  * @return number of microseconds to delay the wakeup.
  */
 int32_t AAudioProperty_getWakeupDelayMicros();
-
 #define AAUDIO_PROP_WAKEUP_DELAY_USEC      "aaudio.wakeup_delay_usec"
 
 /**
@@ -139,7 +133,6 @@ int32_t AAudioProperty_getWakeupDelayMicros();
  * @return minimum number of microseconds to sleep.
  */
 int32_t AAudioProperty_getMinimumSleepMicros();
-
 #define AAUDIO_PROP_MINIMUM_SLEEP_USEC      "aaudio.minimum_sleep_usec"
 
 /**
@@ -153,7 +146,21 @@ int32_t AAudioProperty_getMinimumSleepMicros();
  * @return minimum number of microseconds for a MMAP HW burst
  */
 int32_t AAudioProperty_getHardwareBurstMinMicros();
+#define AAUDIO_PROP_HW_BURST_MIN_USEC      "aaudio.hw_burst_min_usec"
+
+/**
+ * Read a system property that specifies an offset that will be added to MMAP timestamps.
+ * This can be used to correct bias in the timestamp.
+ * It can also be used to analyze the time distribution of the timestamp
+ * by progressively modifying the offset and listening for glitches.
+ *
+ * @return number of microseconds to offset the time part of an MMAP timestamp
+ */
+int32_t AAudioProperty_getInputMMapOffsetMicros();
+#define AAUDIO_PROP_INPUT_MMAP_OFFSET_USEC    "aaudio.in_mmap_offset_usec"
 
+int32_t AAudioProperty_getOutputMMapOffsetMicros();
+#define AAUDIO_PROP_OUTPUT_MMAP_OFFSET_USEC   "aaudio.out_mmap_offset_usec"
 
 /**
  * Is flush allowed for the given state?