Motion - Bug Report 2007x 01x 17x 201031
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BUG: vloopback-hwscan

I got vloopback loaded (via modprobe vloopback). Then I started resize: nohup resize /dev/video0 /dev/video1 320x240 320x240 yuv420p &> /dev/null &

After that "xawtv -c /dev/video2" works.

But "xawtv -hwscan" hangs. It goes through only if resize is killed.

Does vloopback interfere with "-hwscan" ?

# resize is not running
$ xawtv -hwscan
This is xawtv-3.95, running on Linux/i686 (2.6.17-5mdv)
looking for available devices
port 73-73
    type : Xvideo, image scaler
    name : Intel(R) Video Overlay

/dev/video0: OK                         [ -device /dev/video0 ]
    type : v4l
    name : OV518 USB Camera
    flags:  capture

ioctl: VIDIOC_QUERYCAP(driver="";card="";bus_info="";version=0.0.0;capabilities=0x0 []): Unknown error 515
/dev/video1: OK                         [ -device /dev/video1 ]
    type : v4l
    name : Video loopback 0 input
    flags:

/dev/video2: Invalid argument

# now start resize
$ resize /dev/video0 /dev/video1 320x240 320x240 yuv420p
Starting video stream.

#########################################################
# In a different shell

# /dev/video2 now works
$ xawtv -c /dev/video2
This is xawtv-3.95, running on Linux/i686 (2.6.17-5mdv)
/dev/video2 [v4l]: no overlay support
v4l-conf had some trouble, trying to continue anyway
ioctl: VIDIOC_QUERYCAP(driver="";card="";bus_info="";version=0.0.0;capabilities=0x0 []): Unknown error 515
libGL warning: 3D driver claims to not support visual 0x4b
libGL warning: 3D driver claims to not support visual 0x23
libGL warning: 3D driver claims to not support visual 0x25
libGL warning: 3D driver claims to not support visual 0x27
libGL warning: 3D driver claims to not support visual 0x29
libGL warning: 3D driver claims to not support visual 0x2b
libGL warning: 3D driver claims to not support visual 0x2d
libGL warning: 3D driver claims to not support visual 0x2f
libGL warning: 3D driver claims to not support visual 0x31
ioctl: VIDIOCMCAPTURE(frame=0;height=20;width=20;format=7): Invalid argument

# but this hangs
$ xawtv -hwscan
This is xawtv-3.95, running on Linux/i686 (2.6.17-5mdv)
looking for available devices
port 73-73
    type : Xvideo, image scaler
    name : Intel(R) Video Overlay

##########  now killed resize ###############
# resumes after resize is killed

/dev/video0: OK                         [ -device /dev/video0 ]
    type : v4l
    name : OV518 USB Camera
    flags:  capture

ioctl: VIDIOC_QUERYCAP(driver="";card="";bus_info="";version=0.0.0;capabilities=0x0 []): Unknown error 515
/dev/video1: OK                         [ -device /dev/video1 ]
    type : v4l
    name : Video loopback 0 input
    flags:

/dev/video2: Invalid argument

Environment

Motion version:  
ffmpeg version: 0.4.9-3.pre1
Shared libraries:  
Server OS: Mandriva 2007, kernel 2.6.17-5mdv

-- ChittaMandal - 17 Jan 2007

Follow up

Fix record

vloopback doesn't support V4L2 only V4L.

ioctl: VIDIOC_QUERYCAP(driver="";card="";bus_info="";version=0.0.0;capabilities=0x0 []): Unknown error 515

That ioctl is only for V4L2 , so i have change vloopback error when a ioctl is not supported. Changed -ENOIOCTLCMD by more appropiate error -ENOTTY.

Moreover vloopback doesn't support to be open/access by more that 1 process at same time, so if it's already open you will experience undefined result.

Correction : vloopback can be opened by many application but without using exclusive mode.

And last i don't know how hwscan works , but maybe will use some V4L2 call that is not working fine with vloopback.

So i know that vloopback need to be ported to V4L2 , but i have not time , you can take a look to vivi that is a virtual V4L2 device.

-- AngelCarpintero - 18 Jan 2007
Topic revision: r3 - 24 Jan 2007, AngelCarpintero
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