Video capture on EOS 650d only with 4 to 8 fps?

Hi,

I am trying to use an EOS 650d for video streaming. Ideally, I'd like
to use it as high-quality webcam vor conferencing. Before going into
details: Is that even feasible? I've read about a 2 second delay that
you don't get rid of. If that is a hardware property, this ends much of
the fun right away and I'm better off buying a normal UVC cam. But I
was curious if I could use the superior optics of the DSLR.

Test platform is a Core i7 laptop with Ubuntu 20.04. I switch on the
camera for video, then run

	gphoto2 --capture-movie=10s
.
This does record video and creates a file movie.mjpg. But it records
way to few frames. It tells me it recorded 44 frames for 10 seconds of
video. MPlayer plays with 25 fps for some accelerated motion …

Likewise, if I stream to v4l2loopback the live view on the laptop is
jerky, with the low framerate.

gphoto2 --stdout --capture-movie | ffmpeg -i - -vcodec rawvideo -pix_fmt yuv420p -threads 2 -f v4l2 /dev/video0
Nehme Vorschaubilder als Film in 'stdout' auf. Drücke Ctrl-C zum abbrechen.
ffmpeg version 4.2.4-1ubuntu0.1 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 9 (Ubuntu 9.3.0-10ubuntu2)
  configuration: --prefix=/usr --extra-version=1ubuntu0.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --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-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-nvenc --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
[mjpeg @ 0x5647c56f7780] 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), 960x640, 25 tbr, 1200k tbn, 25 tbc
Stream mapping:
  Stream #0:0 -> #0:0 (mjpeg (native) -> rawvideo (native))
[swscaler @ 0x5647c5754740] deprecated pixel format used, make sure you did set range correctly
Output #0, video4linux2,v4l2, to '/dev/video0':
  Metadata:
    encoder         : Lavf58.29.100
    Stream #0:0: Video: rawvideo (I420 / 0x30323449), yuv420p, 960x640, q=2-31, 184320 kb/s, 25 fps, 25 tbn, 25 tbc
    Metadata:
      encoder         : Lavc58.54.100 rawvideo
frame=   27 fps=5.2 q=-0.0 size=N/A time=00:00:01.08 bitrate=N/A speed=0.208x 

Now the fps settles around 4.something, I had 8 fps before. But never smooth.

Is 8 fps all that I can get from the camera? The live view on the TFT of
the camera looks smooth during capture.


Alrighty then,

Thomas


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