Re: rc cameras, section 'video conferencing'. ffmpeg/v4l2 options currently still valid?

Hi,

Your video4linux loopback device might not be set up on /dev/video0,
so this might be your regular webcam.

So try /dev/video1 or /dev/video2 or higher until you get the v4l2 loopback device.

CIao, Marcus

On Thu, Dec 09, 2021 at 06:52:29PM +0100, Ulrich Salaschek wrote:
> Hi to all,
> 
> first, the obligatory Thank You for gphoto!!
> 
> using a command from the wiki, I encountered an error message though, aiming
> to use my Nikon D7100 as a webcam.
> 
> When running
> $ gphoto2 --stdout --capture-movie | ffmpeg -i - -vcodec rawvideo -pix_fmt
> yuv420p -threads 0 -f v4l2 /dev/video0
> the camera's mirror opens but then gphoto aborts with the following error
> message from ffmpeg/v4l2
> 
> 
> [error message]
> gphoto2 --stdout --capture-movie | ffmpeg -i - -vcodec rawvideo -pix_fmt
> yuv420p -threads 0 -f v4l2 /dev/video0
> ffmpeg version 4.4-6ubuntu5 Copyright (c) 2000-2021 the FFmpeg developers
>   built with gcc 11 (Ubuntu 11.2.0-7ubuntu1)
>   configuration: --prefix=/usr --extra-version=6ubuntu5 --toolchain=hardened
> --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu
> --arch=amd64 --enable-gpl --disable-stripping --enable-gnutls
> --enable-ladspa --enable-libaom --enable-libass --enable-libbluray
> --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2
> --enable-libdav1d --enable-libflite --enable-libfontconfig
> --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm
> --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg
> --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq
> --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr
> --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora
> --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx
> --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid
> --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx
> --enable-openal --enable-opencl --enable-opengl --enable-sdl2
> --enable-pocketsphinx --enable-librsvg --enable-libmfx --enable-libdc1394
> --enable-libdrm --enable-libiec61883 --enable-nvenc --enable-chromaprint
> --enable-frei0r --enable-libx264 --enable-shared
>   libavutil      56. 70.100 / 56. 70.100
>   libavcodec     58.134.100 / 58.134.100
>   libavformat    58. 76.100 / 58. 76.100
>   libavdevice    58. 13.100 / 58. 13.100
>   libavfilter     7.110.100 /  7.110.100
>   libswscale      5.  9.100 /  5.  9.100
>   libswresample   3.  9.100 /  3.  9.100
>   libpostproc    55.  9.100 / 55.  9.100
> Nehme Vorschaubilder als Film in 'stdout' auf. Drücke Ctrl-C zum abbrechen.
> [mjpeg @ 0x5633a608f440] Format mjpeg detected only with low score of 25,
> misdetection possible!
> Input #0, mjpeg, from 'pipe:':
>   Duration: N/A, bitrate: N/A
>   Stream #0:0: Video: mjpeg (Baseline), yuvj422p(pc,
> bt470bg/unknown/unknown), 640x360, 25 tbr, 1200k tbn, 25 tbc
> Stream mapping:
>   Stream #0:0 -> #0:0 (mjpeg (native) -> rawvideo (native))
> [swscaler @ 0x5633a60f7b80] deprecated pixel format used, make sure you did
> set range correctly
> [video4linux2,v4l2 @ 0x5633a6092f40] ioctl(VIDIOC_G_FMT): Invalid argument
> Could not write header for output file #0 (incorrect codec parameters ?):
> Invalid argument
> Error initializing output stream 0:0 --
> Conversion failed!
> [/error message]
> 
> 
> Help is appreciated.
> Kind regards
> Ulrich
> 
> 
> 
> Running Ubuntu 21.10 with Kernel 5.13.0-22
> v4l2loopback kernel module is installed and loaded alongside videodev
> $ gphoto2 --summary displays the camera infos correctly
> $ gphoto2 --capture-image-and-download and other commands work as expected
> 
> Versions:
> This version of gphoto2 is using the following software versions and
> options:
> gphoto2         2.5.27         gcc, popt(m), exif, cdk, aa, jpeg, readline
> libgphoto2      2.5.27         standard camlibs, gcc, ltdl, EXIF
> libgphoto2_port 0.12.0         iolibs: disk ptpip serial usb1 usbdiskdirect
> usbscsi, gcc, ltdl, EXIF, USB, serial without locking
> 
> 
> 
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