Zero-Copy

Two processes on a Jetson, one camera frame in NVMM (GPU memory), no copies. The kernel does the heavy lifting via dma-buf fds; SCM_RIGHTS carries the fd across the process boundary; NvBufSurfaceImport reconstructs the surface on the consumer side; a cache-line-padded ring of atomic ref-counts keeps fan-out coherent without locks. With benchmark numbers and a Godbolt-runnable demo of the SCM_RIGHTS pattern.

A sequel to the first STM32H750 tracker post. After the C++ port was proven in production, I spent a week of evenings cutting dead vendor code, splitting the algorithm out to host for unit tests, wiring the LCD SPI through DMA to let the CPU run the tracker in parallel with the blit, unlocking the camera’s real frame rate, chasing a subtle BB-drift bug back to a too-wide SAD search, and finally building an offline A/B harness that compares SAD, NCC, and MOSSE on four synthetic scenarios so the next tracker port is a data decision, not a vibes one.

How we built a GStreamer plugin suite for zero-copy NVMM video on NVIDIA Jetson, the bugs we hit along the way, and what it takes to contribute to the GStreamer project — from filing issues to getting an MR merged.