getting gst-launch-1.0 nvcamerasrc to work with v4l2loopback

[kclim2]

• v4l2loopback version: v4l2loopback driver version 0.9.1

• kernel version: Linux tegra-ubuntu 3.10.96-test gstreamer v4l2sink support #1 SMP PREEMPT Mon Dec 5 17:28:33 CST 2016 aarch64 aarch64 aarch64 GNU/Linux

*lsb
lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 16.04 LTS
Release: 16.04
Codename: xenial

I made a post on nvidia developer forum on getting gst-launch-1.0 nvcamerasrc to work with v4l2loopback. Please help to shed some light if possible.

https://devtalk.nvidia.com/default/topic/994012/jetson-tx1/passing-gst-launch-from-nvcamerasrc-to-v4l2sink/

[umlaeute]

please try again with v4l2loopback-0.10

Apart from that, the cannot identify device /dev/video3 error suggests that there is no /dev/video3 file.
v4l2loopback will create device-files at the module-load stage (rather than dynamically).
So if you have a physical /dev/video0 and you want 3 loopback devices (dev/video1../dev/video3) you ought to load the module like:

sudo modprobe v4l2loopback devices=3

[kclim2]

Hi umlaeute,

Thanks for the prompt response.

we originally using v4l2loopback-0.10 with nvidia TX1 Linux tegra-ubuntu 3.10.96 aarch64 GNU/Linux (see https://devtalk.nvidia.com/default/topic/988447/?comment=5081657 for the error detail).

we then realized v4l2loopback 0.9 doesn't give us the error (able to use guvcview to consume the created v4l2loopback adapter /dev/video3 with producer grabbing an USB webcam /dev/video0) but fail to get it working with nvcamerasrc at our /dev/video1 (see error as follow):

gst-launch-1.0 --gst-debug-level=3 nvcamerasrc ! 'video/x-raw(memory:NVMM), width=(int)1920, height=(int)1080, format=(string)I420, framerate=(fraction)30/1' ! nvtee ! nvvidconv flip-method=2 ! 'video/x-raw(memory:NVMM), format=(string)I420, framerate=(fraction)30/1' ! v4l2sink device=/dev/video3
0:00:00.042475886 7498 0x59a0c0 ERROR GST_PIPELINE grammar.y:642:gst_parse_perform_link: could not link nvvconv0 to v4l2sink0

(see more error detail and nvcamerasrc' capability from https://devtalk.nvidia.com/default/topic/994012/?comment=5085953 )

Wish you could help to analyze the possible source of error.

PS: please ignore the error message produced by DaneLLL who was trying to help to resolve the issue (i believe DaneLLL didn't create his /dev/video3 at all)

Apart from that, the cannot identify device /dev/video3 error suggests that there is no /dev/video3 file.
v4l2loopback will create device-files at the module-load stage (rather than dynamically).

[umlaeute]

v4l2loopback-0.10 fixed some major issues with GStreamer-1.0, I don't think that going back to 0.9 should be considered an option.

If guvcview doesn't work with 0.10 (but with 0.9), then this should be fixed instead.

otoh, guvcview (2.0.4) works nicely here (my desktop machine, running Debian/sid on an amd64), and the all references to this program i found in the forums you linked to say:

guvcview has no problem to open the v4l2loopback device

so i'm not sure what the issue is that you are describing (apart from "it doesn't work")

[kclim2]

the loopback device is created at /dev/video1

gst-launch gives the following errors:

gst-launch-1.0 v4l2src device=/dev/video1 ! xvimagesink
Setting pipeline to PAUSED ...
Pipeline is live and does not need PREROLL ...
Setting pipeline to PLAYING ...
New clock: GstSystemClock
0:00:00.265454948 14712       0x6fd940 ERROR          v4l2allocator gstv4l2allocator.c:1299:gst_v4l2_allocator_dqbuf:<v4l2src0:pool:src:allocator> buffer 1 was not queued, this indicate a driver bug.
0:00:00.265566042 14712       0x6fd940 WARN                 v4l2src gstv4l2src.c:884:gst_v4l2src_create:<v4l2src0> error: Failed to allocate a buffer
0:00:00.265689167 14712       0x6fd940 WARN                 basesrc gstbasesrc.c:2948:gst_base_src_loop:<v4l2src0> error: Internal data flow error.
0:00:00.265725156 14712       0x6fd940 WARN                 basesrc gstbasesrc.c:2948:gst_base_src_loop:<v4l2src0> error: streaming task paused, reason error (-5)
ERROR: from element /GstPipeline:pipeline0/GstV4l2Src:v4l2src0: Failed to allocate a buffer
Additional debug info:
gstv4l2src.c(884): gst_v4l2src_create (): /GstPipeline:pipeline0/GstV4l2Src:v4l2src0
Execution ended after 0:00:00.075286250
Setting pipeline to PAUSED ...
Setting pipeline to READY ...
Setting pipeline to NULL ...
Freeing pipeline ...

using guvcview --device=/dev/video1 is able to open the loopback device without giving any problem.

[beniwtv]

Yeah I get the same error as above. Gucview can open the device, but gstreamer can't.

Producer (from a real webcam):
gst-launch-1.0 v4l2src device=/dev/video0 ! v4l2sink device=/dev/video102

Consumer:

gst-launch-1.0 v4l2src device=/dev/video102 ! xvimagesink

v4l2loopback-dkms 0.1.0-1 on Ubuntu 17.10

[windzu]

Hi umlaeute,

Thanks for the prompt response.

we originally using v4l2loopback-0.10 with nvidia TX1 Linux tegra-ubuntu 3.10.96 aarch64 GNU/Linux (see https://devtalk.nvidia.com/default/topic/988447/?comment=5081657 for the error detail).

we then realized v4l2loopback 0.9 doesn't give us the error (able to use guvcview to consume the created v4l2loopback adapter /dev/video3 with producer grabbing an USB webcam /dev/video0) but fail to get it working with nvcamerasrc at our /dev/video1 (see error as follow):

gst-launch-1.0 --gst-debug-level=3 nvcamerasrc ! 'video/x-raw(memory:NVMM), width=(int)1920, height=(int)1080, format=(string)I420, framerate=(fraction)30/1' ! nvtee ! nvvidconv flip-method=2 ! 'video/x-raw(memory:NVMM), format=(string)I420, framerate=(fraction)30/1' ! v4l2sink device=/dev/video3
0:00:00.042475886 7498 0x59a0c0 ERROR GST_PIPELINE grammar.y:642:gst_parse_perform_link: could not link nvvconv0 to v4l2sink0

(see more error detail and nvcamerasrc' capability from https://devtalk.nvidia.com/default/topic/994012/?comment=5085953 )

Wish you could help to analyze the possible source of error.

PS: please ignore the error message produced by DaneLLL who was trying to help to resolve the issue (i believe DaneLLL didn't create his /dev/video3 at all)

Apart from that, the cannot identify device /dev/video3 error suggests that there is no /dev/video3 file.
v4l2loopback will create device-files at the module-load stage (rather than dynamically).

Hello, I ran the same test on xavier and encountered the same problem as you, did you solve this problem in the end?

[umlaeute]

liberal adding of tee elements often helps...

[umlaeute]

i did a quick google-check and found this:

The nvv4l2camerasrc plugin default currently supports only DMABUF (importer role) streaming I/O mode with V4L2_MEMORY_DMABUF.

the v4l2loopback device currently only supports V4L2_MEMORY_MMAP, so that might explain why it's not working.

i'm therefore closing this as a duplicate of #501 (in case you wonder: #501 is about the underlying issue, whereas this bug-report is about a symptom; hence i'm closing this one in favour of the other)