Running the video stream¶
Streaming from the SDI-MIPI bridge to the chosen board is done through the MIPI CSI interface in a 2 or 4 lane configuration. The SDI to MIPI bridge supports only the YUV422 format in 1080p (30 or 60 FPS) or 720p (60 FPS) resolution.
Loading the bitstream¶
Different resolutions and framerates require different bitstreams.
Therefore the FPGA manager subsystem in the Linux kernel is used to reprogram the FPGA as needed.
In order to load the bitstream, first place it in the /lib/firmware/sdi_bridge directory as this is the path where the FPGA Manager looks for files to load.
Once that is done, pass the bitstream’s filename to the load node and wait until the process is finished.
echo "sdi_bridge/<bitstream_name.bit>" | sudo tee /sys/class/fpga_manager/fpga0/load
When the bitstream is loaded, the CDONE LED should be blinking and the USER_LED should be turned on. The USER_LED is wired to the tInit output of the CMOS to D-PHY IP core which activates when the core has been initialized.
Note
The DAT_ERROR LED is turned on if there are no errors and turns off if data errors occur.
By default there are bitstreams for each supported video format located in the /lib/firmware/sdi_bridge directory.
Default bitstreams are named with the following pattern:
<video_format>-<lanes>.bit
For example, to load the 1080p60 2-lanes variant:
echo "sdi_bridge/1080p60-2lanes.bit" | sudo tee /sys/class/fpga_manager/fpga0/load
Important
The lane count of the uploaded bitstream variant must match the device tree used in your Linux kernel.
Setting up the stream¶
If valid SDI signal is present on the SDI-MIPI bridge input, the LOCKED LED turns on.
It indicates that the deserializer was able to acquire lock to the input signal.
To be able to get the proper video data on the device, the video source has to stream in YUV422 format.
Testing the video stream¶
Note
If you see incorrect colors or there is no picture, try pressing the reset button on the SDI Bridge. If that doesn’t help, reload the bitstream.
To test the video stream, you can launch e.g. gstreamer as follows:
gst-launch-1.0 v4l2src device=/dev/video0 ! 'video/x-raw,width=<width>,height=<height>' ! xvimagesink
The <width> and <height> parameters should match the currently used bitstream and SDI video resolution, either 1920x1080 or 1280x720.
To test the video stream, you can use e.g. qv4l2 app.
There, you should set the expected pixel format and resolution according to the video source and loaded bitstream.
Note
Raspberry Pi currently supports only 4-lanes variants.
Also, the v4l2-ctl tool can be used to grab frames:
v4l2-ctl --stream-mmap --set-fmt-video=width=<width>,height=<height>,pixelformat=VYUY --stream-count=0 --stream-to=/dev/null
The <width> and <height> parameters should match the currently used bitstream and SDI video format, either 1920x1080 or 1280x720.
To write captured frames to a file, set your target destination with --stream-to=.
To get the exact number of frames grabbed, set --stream-count=.