clearing data in queue element in a pipeline

[cppb]

I have a code that converts back to back video files. The pipeline looks like the following:

filesrc location="fil1.mov" ! decodebin name="decode"  decode. ! queue ! ffmpegcolorspace ! theoraenc quality=32 ! oggmux name=mux ! filesink location=fil.ogg"decode. ! queue ! audioconvert ! vorbisenc ! queue ! mux.

This works, but the second video file it converts has asynchronus audio and video tracks. In fact most of the audio track is lost. I suspect that the data in the queue is not cleared or there is some buffering problem when it starts the second conversion.... if this is the reason, is there a way to clear data in the queue element?

Is there any other reason why this might be happening?

I tried using gst_element_send_event( qElement*, gst_event_new_flush_start())  but that doesn't work and gives an unhandleled exception.

any replied would be appreciated.