The Frame Buffer is described in this document:
http://www.altera.com/literature/ug/ug_vip.pdf The parameters in question are described on page 20-5 and 20-6.
They do not apply to the image (640x480) data, or the VIP protocol Control Packet. They apply to other protocol (possibly user defined) that might be embedded within the same stream.
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While 1 symbol = 3 color planes (= 1 pixel) => we have 640*480/10 packets per frame.
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Typically you only have (2) packets per frame: one control packet, and one video packet. See Figure 3-14 in the document.