The choice of an external-frame-buffer solution for AXI4-Stream based video systems is the AXI-VDMA core. The AXI-VDMA core supports the AXI4-Stream video interfaces natively, meaning SOF and EOL signals are properly interpreted and generated by the AXI-VDMA core.
As illustrated in This Figure , the AXI-VDMA core supports one master and one slave interface. Slave/Master interfaces can:
• Use any input SOF signals, or an external Frame Sync input as a source to initiate Frame transfers (AXI-VDMA Frame sync crossbar).
• AXI Master interfaces to use any AXI Slave interfaces to be the Gen-lock master.
• AXI Slave interfaces to use any AXI Master interfaces to be the Gen-lock master (Genlock crossbar).
Using a Frame sync crossbar enables video systems with a Frame Buffer, but without external output Frame sync source, to automatically retrieve the last frame finished on the write-side. This is picked up immediately after reading a frame has completed on the read side.
Some IP cores, such as the Video On-Screen Display, can have multiple read channels (slave interfaces) which must be synchronized. You might need multiple instances of a slower core running in parallel to achieve sufficient throughput. These parallel core instances can use multiple write channels (master interfaces), which must be synchronized. Operating modes for single write - multiple read ports:
• Genlock mode: Write side and read side individually freewheels.
• Same Frame Readout mode: Write side freewheels, but all read sides need to read out the same frame.
• Synchronizer mode: All frames written need to be read out on all ports.