V4l2src Failed to allocate Buffer when running from camera

Autonomous Machines Jetson & Embedded Systems Jetson Nano
1

Hi all,

I’m trying to use the camera feed from my Jetson Nano in 2 applications at the same time, through the use of v4l2loopback, but I’m having some issues.

I have created 2 v4l2 devices with v4l2loopback, and can successfully run the producer pipeline:

PRODUCER:
gst-launch-1.0 nvarguscamerasrc ! 'video/x-raw(memory:NVMM), width=1920, height=1080, format=NV12, framerate=(fraction)30/1' ! nvvidconv ! tee name=t ! queue ! v4l2sink device=/dev/video1 t. ! queue ! v4l2sink device=/dev/video2

I have successfully created an OpenCV application that uses /dev/video1, so that’s not an issue…

But when I try to view /dev/video2 with the below pipeline, it crashes after displaying the first frame

CONSUMER:
gst-launch-1.0 v4l2src device=/dev/video2 ! xvimagesink

Setting pipeline to PAUSED …
Pipeline is live and does not need PREROLL …
Setting pipeline to PLAYING …
New clock: GstSystemClock
ERROR: from element /GstPipeline:pipeline0/GstV4l2Src:v4l2src0: Failed to allocate a buffer
Additional debug info:
gstv4l2src.c(998): gst_v4l2src_create (): /GstPipeline:pipeline0/GstV4l2Src:v4l2src0
Execution ended after 0:00:00.420358169
Setting pipeline to PAUSED …
Setting pipeline to READY …
Setting pipeline to NULL …
Freeing pipeline …

If I replace the producer with videotestsrc like so, the exact same error happens:
gst-launch-1.0 videotestsrc ! tee name=t ! queue ! v4l2sink device=/dev/video1 t. ! queue ! v4l2sink device=/dev/video2

Anyone have any idea how to fix this buffer issue?

3

Hi,
It looks like you hit constraint of USB bandwidth. Please check
connected more than two usb cameras problem on deepstream-app (Jetson Nano Dev Kit) - #12 by DaneLLL

Suggest use USB3 cameras.

4

Hi DaneLLL,

I’m using an IMX219 CSI camera

But the good news is I’ve found the problem!

Simply add a max_buffers=2 argument to v4l2loopback, and that fixes the problem! So the full command is:
sudo modprobe v4l2loopback video_nr=1,2 max_buffers=2

Not entirely sure why I don’t need that argument on PC, must be to do with the amount of available memory.

Also, curiously, if using a number higher than 2 for max_buffers, it throws the same Failed to allocate buffer error