diff --git a/services/audioflinger/PlaybackTracks.h b/services/audioflinger/PlaybackTracks.h
index 3f62bc3..94ea042 100644
--- a/services/audioflinger/PlaybackTracks.h
+++ b/services/audioflinger/PlaybackTracks.h
@@ -222,6 +222,8 @@
 
 private:
     void                interceptBuffer(const AudioBufferProvider::Buffer& buffer);
+    /** Write the source data in the buffer provider. @return written frame count. */
+    size_t              writeFrames(AudioBufferProvider* dest, const void* src, size_t frameCount);
     template <class F>
     void                forEachTeePatchTrack(F f) {
         for (auto& tp : mTeePatches) { f(tp.patchTrack); }