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5.1. Video and Vision Processing IP Control Examples
In this system, the full variant clipper IP is parameterized to perform a fixed clip of 1080p HD video clipped down to 720p HD video and has no memory-mapped control interface. The clipper parameters always clip to a height and width of 1280x720 pixels. No further control is necessary as information about the incoming video fields is carried in image information control packets (refer to the Intel FPGA streaming video protocol specification). So, if the input resolution changed to 720p, the clipper reads that information from the image information packets and performs no additional clipping.
The figure shows the video protocol packets from the video ingress subsystem. The packets stream into IP1, which doesn’t change the dimensions of the video. It sends the same image information packets and the same number of data packets into the clipper IP.
The figure shows an image information packet with the video field information for a progressive frame of 1920x1080 pixels. Each video packet carries one line of 1920 pixels.
The image information packet from the clipper contains the new field dimensions of 1280x720 and the clipper only outputs 720 video packets, each of 1280 pixels.
Most systems need to control IPs so that you can apply different amounts of clipping, scaling or mixing. In this system, the full variant of the clipper IP now includes a memory-mapped control interface. The clipper IP includes a register map and the processor can read the clipper's parameter information and set clipping offsets for any clipping style that you want. When the processor writes any changes to clipping requirements, a final write to the COMMIT register (or receiving a commit auxiliary control packet) ensures they apply when the IP receives the next image information packet to mark the start of the next field.
The processor can also read the dimensions of the incoming video and the count of incoming fields if you turn on Debug features.
Intel recommends this method of control, which is the simplest and most flexible.
In this example, the lite variant clipper IP is parameterized with the mandatory memory-mapped control interface. In lite variant IPs, the processor writes the field’s properties to the clipper’s IMAGE_INFO registers. The streaming interface just contains video data. Otherwise, control operates as for full variant IPs with memory-mapped control. The processor also writes desired clipping dimensions to the clipper’s register map.
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