I'm not a programmer nor script writer (working to correct script part) but I would investigate a script that could capture and record (more append) the voip packets to a file which at the same time could be accessed and read by your voip playback software. Playback reading packets from the beginning of the file while at the same time the script is writing the latest packets captured to the end of the file. More like a buffer (pipe) between the two. The key, depending on the playback software, is to present this as a readable file to the playback software while it is being accessed by the recording script.