Overview

This sample uses V4L2 image capturing with NVIDIA^® CUDA^® format conversion.

Building and Running

Prerequisites

You have followed Steps 1-3 in Building and Running.
You have installed:
- CUDA Toolkit
A USB camera suppporting YUYV output format is plugged into your target.

To build

Enter:
```
   $ cd v4l2cuda
   $ make
```

To clean up all generated files

Enter

make clean

To run

Enter:
```
$ ./capture-cuda [options]
```

To view supported options

Enter:
```
$ ./capture-cuda --help
```

Flow

This is the overall process flow of capture-cuda:

            V4L2                          CUDA
USB camera ------> captured image (YUYV) ------> converted image (RGB)

As shown in the following diagrams, the buffer flow differs depending on V4L2 capturing modes and CUDA memory management.

V4L2 memory-mapped buffers (V4L2_MEMORY_MMAP) are allocated in kernel space. The application maps them in user space and copies them to the CUDA device allocated memory for CUDA processing.

The application allocates V4L2 user-space buffers (V4L2_MEMORY_USERPTR). In this situation, the driver directly fills in the user-space memory. When you allocate CUDA-mappable memory (with cudaHostAlloc), the CUDA device can access the V4L2 captured buffer without memory copy.

Using Memory-Mapped Buffers (-m option)

$ ./capture-cuda -d /dev/video0 -m

   _                       _              _           _
  | |  mmap        copy   | |  convert   | |  copy   | |  write
  |_| ------> ptr ------> |_| =========> |_| ------> |_| -------> file
        |
kernel  |  user

Using Memory-Mapped Buffers and Zero-Copy CUDA Memory (-m and -z options)

$ ./capture-cuda -d /dev/video0 -m -z

   _                       _              _
  | |  mmap        copy   | |  convert   | |  write
  |_| ------> ptr ------> |_| =========> |_| -------> file
        |
kernel  |  user

Using Application-Allocated Buffers (-u option)

$ ./capture-cuda -d /dev/video0 -u

               _           _              _           _
    userptr   | |  copy   | |  convert   | |  copy   | |  write
   ---------> |_| ------> |_| =========> |_| ------> |_| -------> file
        |
kernel  |  user

Using Application-Allocated Buffers and Zero-Copy CUDA Memory (-u and -z options)

$ ./capture-cuda -d /dev/video0 -u -z

               _              _
    userptr   | |  convert   | |  write
   ---------> |_| =========> |_| -------> file
        |
kernel  |  user

Jetson Linux Multimedia API Reference

32.4.2 Release