[Discuss-gnuradio] ALSA Source

Hello,   I have acoustic modem which uses ALSA source as interface to outside world. I use a preamble based time synchronization technique to find start of data in the frame. But my synchronization method is taking too long and in the process i think i am loosing incoming samples from ALSA source. Is there a way to buffer samples from ALSA source , until i finish synchronization. Please provide me some suggestions. Thanks in advance, Ram