Video and Image Processing Suite User Guide

ID 683416
Date 2/12/2021

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16.4. Handling of Avalon-ST Video Control Packets and User Packets

The Frame Buffer II IP core stores non-image data packets in memory.

Some applications may repeat and drop the user packets together with their associated frame. For example, if the packets contain frame-specific information such as a frame ID.

The behavior of the IP core is not determined by the field dimensions announced in the Avalon-ST Video control packets and relies exclusively on the startofpacket and endofpacket signals to delimit the frame boundaries.
  • The IP core consequently handles and propagates mislabeled frames. Use this feature in a system where you cannot drop a frame. The latency introduced during the buffering could provide enough time to correct the invalid control packet.
  • The buffering and propagation of image data packets incompatible with preceding control packets is an undesired behavior in most systems. Dropping invalid frames is often a convenient and acceptable way of dealing with glitches from the video input.

You can parameterize the Frame Buffer II IP core to drop all mislabeled fields or frames at compile time.

To drop and repeat user packets:
  • Set the user packet affinity bit (bit 1) of the Misc. register.
  • Turn on Drop invalid frames parameter.

Turn on the Frame repeating parameter to guarantee that reader keeps on repeating the last valid received frame— freezes the output—when the input drops.