diff --git a/services/audioflinger/TrackBase.h b/services/audioflinger/TrackBase.h
index 8f720b5..7a3bb0d 100644
--- a/services/audioflinger/TrackBase.h
+++ b/services/audioflinger/TrackBase.h
@@ -325,6 +325,7 @@
 
     virtual ~PatchProxyBufferProvider() {}
 
+    virtual bool        producesBufferOnDemand() const = 0;
     virtual status_t    obtainBuffer(Proxy::Buffer* buffer,
                                      const struct timespec *requested = NULL) = 0;
     virtual void        releaseBuffer(Proxy::Buffer* buffer) = 0;
@@ -347,6 +348,8 @@
                             mPeerProxy = nullptr;
                         }
 
+            bool        producesBufferOnDemand() const override { return false; }
+
 protected:
     const sp<ClientProxy>       mProxy;
     sp<RefBase>                 mPeerReferenceHold;   // keeps mPeerProxy alive during access.