AudioSystem: add API to query audio HW sync source

Add a method to query from the audio HAL the HW sync
source used for a given audio session.
Modify audio policy to select a direct output with HW sync
when requested.

Bug: 16132368.

Change-Id: I03038f9188f2d389f8a5fd76a671854013a4513e

3 files changed, 33 insertions, 2 deletions

diff --git a/services/audioflinger/AudioFlinger.cpp b/services/audioflinger/AudioFlinger.cpp
index b8cc33a..1f77b2f 100644
--- a/services/audioflinger/AudioFlinger.cpp
+++ b/services/audioflinger/AudioFlinger.cpp
@@ -1579,6 +1579,25 @@ status_t AudioFlinger::setLowRamDevice(bool isLowRamDevice)
     return NO_ERROR;
 }
 
+audio_hw_sync_t AudioFlinger::getAudioHwSyncForSession(audio_session_t sessionId)
+{
+    Mutex::Autolock _l(mLock);
+    for (size_t i = 0; i < mPlaybackThreads.size(); i++) {
+        sp<PlaybackThread> thread = mPlaybackThreads.valueAt(i);
+        if ((thread->hasAudioSession(sessionId) & ThreadBase::TRACK_SESSION) != 0) {
+            // A session can only be on one thread, so exit after first match
+            String8 reply = thread->getParameters(String8(AUDIO_PARAMETER_STREAM_HW_AV_SYNC));
+            AudioParameter param = AudioParameter(reply);
+            int value;
+            if (param.getInt(String8(AUDIO_PARAMETER_STREAM_HW_AV_SYNC), value) == NO_ERROR) {
+                return value;
+            }
+            break;
+        }
+    }
+    return AUDIO_HW_SYNC_INVALID;
+}
+
 // ----------------------------------------------------------------------------
 
 
diff --git a/services/audioflinger/AudioFlinger.h b/services/audioflinger/AudioFlinger.h
index 31c5a1a..4e9d49b 100644
--- a/services/audioflinger/AudioFlinger.h
+++ b/services/audioflinger/AudioFlinger.h
@@ -248,6 +248,9 @@ public:
     /* Set audio port configuration */
     virtual status_t setAudioPortConfig(const struct audio_port_config *config);
 
+    /* Get the HW synchronization source used for an audio session */
+    virtual audio_hw_sync_t getAudioHwSyncForSession(audio_session_t sessionId);
+
     virtual     status_t    onTransact(
                                 uint32_t code,
                                 const Parcel& data,
diff --git a/services/audiopolicy/AudioPolicyManager.cpp b/services/audiopolicy/AudioPolicyManager.cpp
index c519593..c00541c 100644
--- a/services/audiopolicy/AudioPolicyManager.cpp
+++ b/services/audiopolicy/AudioPolicyManager.cpp
@@ -118,6 +118,7 @@ const StringToEnum sFlagNameToEnumTable[] = {
     STRING_TO_ENUM(AUDIO_OUTPUT_FLAG_DEEP_BUFFER),
     STRING_TO_ENUM(AUDIO_OUTPUT_FLAG_COMPRESS_OFFLOAD),
     STRING_TO_ENUM(AUDIO_OUTPUT_FLAG_NON_BLOCKING),
+    STRING_TO_ENUM(AUDIO_OUTPUT_FLAG_HW_AV_SYNC),
 };
 
 const StringToEnum sFormatNameToEnumTable[] = {
@@ -671,12 +672,17 @@ audio_io_handle_t AudioPolicyManager::getOutputForAttr(const audio_attributes_t
         ALOGE("getOutputForAttr() called with NULL audio attributes");
         return 0;
     }
-    ALOGV("getOutputForAttr() usage=%d, content=%d, tag=%s",
-            attr->usage, attr->content_type, attr->tags);
+    ALOGV("getOutputForAttr() usage=%d, content=%d, tag=%s flags=%08x",
+            attr->usage, attr->content_type, attr->tags, attr->flags);
 
     // TODO this is where filtering for custom policies (rerouting, dynamic sources) will go
     routing_strategy strategy = (routing_strategy) getStrategyForAttr(attr);
     audio_devices_t device = getDeviceForStrategy(strategy, false /*fromCache*/);
+
+    if ((attr->flags & AUDIO_FLAG_HW_AV_SYNC) != 0) {
+        flags = (audio_output_flags_t)(flags | AUDIO_OUTPUT_FLAG_HW_AV_SYNC);
+    }
+
     ALOGV("getOutputForAttr() device %d, samplingRate %d, format %x, channelMask %x, flags %x",
           device, samplingRate, format, channelMask, flags);
 
@@ -746,6 +752,9 @@ audio_io_handle_t AudioPolicyManager::getOutputForDevice(
     if ((flags & AUDIO_OUTPUT_FLAG_COMPRESS_OFFLOAD) != 0) {
         flags = (audio_output_flags_t)(flags | AUDIO_OUTPUT_FLAG_DIRECT);
     }
+    if ((flags & AUDIO_OUTPUT_FLAG_HW_AV_SYNC) != 0) {
+        flags = (audio_output_flags_t)(flags | AUDIO_OUTPUT_FLAG_DIRECT);
+    }
 
     // Do not allow offloading if one non offloadable effect is enabled. This prevents from
     // creating an offloaded track and tearing it down immediately after start when audioflinger