Converting color format with zero copy using hardware

Autonomous Machines Jetson & Embedded Systems Jetson AGX Xavier
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1

I am using sample 07_video_convert as my reference. I would like to convert from yuv to rgb. I successfully converted a yuv file to rgb. Now I would like to convert camera frames from yuv to rgb. I have noticed from the code that there are two operations that need to be done. A read and a write operation and each one of them requires copying data from/to pointers returned by NvBufferMemMap. This means that data is copied twice. Is there a way to avoid those two copy operations?

3

Hi,
Is your camera a Bayer sensor, YUV snesor or USB camera? If the frame data is captured into NvBuffer directly you can call NvBufferTransform() to convert YUV420 to RGBA.

4

Its a gmsl camera and we are using V4L2_MEMORY_MMAP to get the data from the camera. The camera does not support V4L2_MEMORY_USRPTR, but I think it could support V4L2_MEMORY_DMABUF

5

Hi,
Please execute the command and share the information for reference:

$ v4l2-ctl -d /dev/videoX --list-formats-ext

Would like to know what formats are supported.

6 
v4l2-ctl -d /dev/video0 --list-formats-ext
ioctl: VIDIOC_ENUM_FMT
	Index       : 0
	Type        : Video Capture
	Pixel Format: 'UYVY'
	Name        : UYVY 4:2:2
		Size: Discrete 1280x720
			Interval: Discrete 0.033s (30.000 fps)

	Index       : 1
	Type        : Video Capture
	Pixel Format: 'NV16'
	Name        : Y/CbCr 4:2:2
		Size: Discrete 1280x720
			Interval: Discrete 0.033s (30.000 fps)

	Index       : 2
	Type        : Video Capture
	Pixel Format: 'UYVY'
	Name        : UYVY 4:2:2
		Size: Discrete 1280x720
			Interval: Discrete 0.033s (30.000 fps)
7

We are using UYVY format 4:2:2

8

Hi,
Please try to run this sample with your camera:

/usr/src/jetson_multimedia_api/samples/12_camera_v4l2_cuda/

If you can run it successfully, please modify this line:

-    input_params.colorFormat = get_nvbuff_color_fmt(V4L2_PIX_FMT_YUV420M);
+    input_params.colorFormat = NvBufferColorFormat_ABGR32;
    input_params.nvbuf_tag = NvBufferTag_NONE;
    /* Create Render buffer */
    if (-1 == NvBufferCreateEx(&ctx->render_dmabuf_fd, &input_params))

By default the YUV422(YUYV or UYVY) frame data is converted to YUV420 for rendering. You can change to RGBA and try.

9

Yes it does work, thank you.

11

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