Set low latency audio buffer size to 4 ms

Change-Id: Ib11deace70b9800a2534df9ac339667a72145d90
diff --git a/CleanSpec.mk b/CleanSpec.mk
index 140a686..ac7af60 100644
--- a/CleanSpec.mk
+++ b/CleanSpec.mk
@@ -64,3 +64,4 @@
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/build.prop)
 $(call add-clean-step, rm -rf $(PRODUCT_OUT)/system/build.prop)
 $(call add-clean-step, rm -f $(PRODUCT_OUT)/system/build.prop)
+$(call add-clean-step, rm -f $(PRODUCT_OUT)/system/build.prop)
diff --git a/device.mk b/device.mk
index d6a76e4..3e14931 100644
--- a/device.mk
+++ b/device.mk
@@ -363,3 +363,7 @@
 # Reduce client buffer size for fast audio output tracks
 PRODUCT_PROPERTY_OVERRIDES += \
     af.fast_track_multiplier=1
+
+# Low latency audio buffer size in frames
+PRODUCT_PROPERTY_OVERRIDES += \
+    audio_hal.period_size=192