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• Anomalie #3815 : sql_updateq qui ne fait pas de jointure

  10 août 2016, par Ybbet SPIP

  Donc, ce que tu veux dire, c’est qu’il n’est pas possible de faire ce type de requête avec l’API de SPIP ?
  

  1. <span class="CodeRay"><span class="class">UPDATE</span> spip_mots <span class="keyword">as</span> mots, spip_groupes_mots <span class="keyword">as</span> groupes <span class="class">SET</span> mots.type=groupes.titre <span class="keyword">WHERE</span> mots.id_groupe=groupes.id_groupe
  2. </span>

  Télécharger

  Cette requête MySQL est pourtant "commune".
  Bien entendu, on peut lancer cette requête avec la fonction sql_query()

• v4l2loopback+ffmpeg input for uvc gadget

  13 mai, par Mosi

  I'm trying to use an MP4 video file as the input for a UVC Gadget setup on my Raspberry Pi 4 Model B, but I'm running into an issue when streaming through V4L2.

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  Goal :

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  To emulate a webcam that streams a looping MP4 video file to a Windows 11 host.

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  My setup :

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  • Hardware : Raspberry Pi 4 Model B

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  • OS : Raspberry Pi OS Lite 64-bit (2025-05-06-raspios-bookworm-arm64-lite)

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  • Kernel : 6.12.25+rpt-rpi-v8

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  • Host System : Windows 11

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  • UVC Gadget version : v0.3.0

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  Workflow :

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  [MP4 Video] → [FFmpeg] → [V4L2 Loopback] → [UVC Gadget] → Windows sees virtual webcam


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  What works :

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  The UVC Gadget works perfectly when I use a real webcam as the source (e.g., /dev/video0). Windows detects the virtual webcam and displays a smooth video stream.

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  The problem :

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  When I try to use an MP4 video file through FFmpeg and send it to the loopback device (/dev/video3), the UVC Gadget fails with the following error :

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  Command I'm using :

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  ffmpeg -re -stream_loop -1 -i input.mp4 -vf scale=640:480 \
  -c:v rawvideo -pix_fmt yuyv422 -r 30 -f v4l2 /dev/video3


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  Then I run :

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  sudo uvc-gadget -d /dev/video3 uvc.0


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  Output :

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  bRequestType 21 bRequest 01 wValue 0200 wIndex 0001 wLength 0022
streaming request (req SET_CUR cs 02)
setting commit control, length = 34
Setting format to 0x56595559 640x480
=== Setting frame rate to 30 fps
Starting video stream.
--> [At this point I open the camera on the Windows host]
/dev/video3: 2 buffers requested.
Failed to export buffer 0.
Failed to export buffers on source: Inappropriate ioctl for device (25)


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  Things I've tried :

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  • Multiple FFmpeg formats, resolutions, and pixel formats

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  • Various ffmpeg buffer and framerate tweaks

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  • Different UVC Gadget versions

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  • GitHub related projects (showcamera, etc.)

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  • Older Raspberry Pi OS versions

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  Most guides and GitHub projects I found are outdated (5+ years old), and newer methods seem undocumented or incompatible with current kernel/UVC gadget tools.

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  My question :

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  How can I stream an MP4 file as a virtual webcam using UVC Gadget without getting ioctl errors ?
  &#xA;Is there a proper way to set up FFmpeg and loopback devices so that UVC Gadget can read the stream correctly ?

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  Any modern working example or tips would be very appreciated. Thanks in advance !

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• What are the gotchas of using statically linked libraries in serverless platforms such as Google Cloud Functions ?

  5 septembre 2017, par Dzh

  Libraries such as ffmpeg-static upload statically linked binaries onto container.

  I wonder what are the drawbacks of using this approach ?

  Does the library size counts against your memory use (it’s billed by GCloud) ?

  Does it slow down the container ? Perhaps some future-proofing issues ?

  Edit : Found something of a related (I wanted to setup OpenCV) on AWS blog. It doesn’t explain drawbacks, just shows how to do it exactly.