What is the point of using speed up and speed down fifo?

Hi,

From the example file on how to use SGDMA core provided by Altera, i found out that, they used speed up fifo, speed down fifo and timing adapter in between 2 sgdma core. picture shows the connection.

What is the point of these speed changing FIFO?? i think they are just there to demo the use of fifo is capable of changing speed. In reality, they dun serve much purpose in this particular design. Am i right?

Regards,

Michael