# Lerobot Camera Backend Issues

**URL:** <https://discuss.huggingface.co/t/lerobot-camera-backend-issues/173200>\
**Category:** Beginners\
**Created:** [February 8, 2026, 7:30am UTC](https://discuss.huggingface.co/t/lerobot-camera-backend-issues/173200 "2026-02-08T07:30:24Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![CursedRock17](https://sea2.discourse-cdn.com/hellohellohello/user_avatar/discuss.huggingface.co/cursedrock17/32/57444_2.png) [@CursedRock17](https://discuss.huggingface.co/u/CursedRock17)\
**Post date:** [February 8, 2026, 7:30am UTC](https://discuss.huggingface.co/t/lerobot-camera-backend-issues/173200/1 "2026-02-08T07:30:24Z")

</div>

**TLDR:** Trained a dataset with 2 cameras just fine, went to record and Lerobot `cv2` backend was screwed up, used temporary fix to force `Video4Linux2`.

### Environment:

- OS: Ubuntu 24.04
- Python: 3.10
- Lerobot: 0.4.2
- FFMPEG: 7.1.1

So recently I was messing with my SO101 arms, had recorded a dataset and left the lab to train my set overnight. When I came back to my machine the morning after, I received a camera issue dealing with the playback through `lerobot-record` via the ACT policy. I kept getting the following error:

```auto
WARNING:lerobot.cameras.opencv.camera_opencv:OpenCVCamera(/dev/video0) failed to set fourcc=MJPG (actual=, success=False). Continuing with default format.
RuntimeError: OpenCVCamera(/dev/video0) failed to set capture_width=640 (actual_width=640, width_success=False).
ioctl(VIDIOC_QBUF): Bad file descriptor

```

Given that the widths were the same I tracked down [the lerobot](https://github.com/huggingface/lerobot/blob/v0.4.2/src/lerobot/cameras/opencv/camera_opencv.py#L273) GitHub to see what causes a failure and it leads back to the `cv2.VideoCapture` class. I’m trying to not use the source version, but the most stable release on PyPi (I had issues with 0.4.3), so I tried a variety of changes to test this difference:

### Various Debug Attempts

- Attempted to record another dataset with the teleoperator: couldn’t access the cameras (same error)
- Made sure the cameras still functioned: Used `gnome-cheese` and `guvcview`: comfirmed both cameras worked fine on both ports in 640x480
- Ensured the ports had proper permissions: they did
- Ran `lerobot-find-cameras opencv`: Received a response with `Detected Cameras` for both, on the correct port, with the correct width/height and FFMPEG backend. Though I did get another error: `ioctl(VIDIOC_QBUF): Bad file descriptor [video4linux2,v4l2 @ 0x5f4ad1cd77c0] and ioctl(VIDIOC_G_INPUT): Inappropriate ioctl for device`
- Ran a simple OpenCV script that called `VideoCapture` by itself with the two various ports: worked
- Closed & Reopened the Terminal and of course turned the computer on and off.
- Entirely removed and reinstalled the `conda` virtual environment: continued getting the issue
- Tried it on another machine: same issue. Then retried all of the above steps

### Current Resolution:

Unfortunately nothing I had tried, worked, I was forced to alter the source variant of lerobot on the 0.4.2 branch. My temporary solution is force [this line](https://github.com/huggingface/lerobot/blob/v0.4.2/src/lerobot/cameras/opencv/camera_opencv.py#L163) to utilize `Video4Linux2`

```auto
Old: self.videocapture = cv2.VideoCapture(self.index_or_path, self.backend)
New: self.videocapture = cv2.VideoCapture(self.index_or_path, cv2.CAP_V4L2)

```

The actually camera utility and rerecording worked. Unfortunately I had other issues, but that’s for me to debug. I have 0 Idea why `lerobot` cannot find the correct backend it was pretty frustrating to take up all that time. I don’t think I’m going to open an official [issue](https://github.com/huggingface/lerobot/issues) unless there’s something that truly wasn’t on me. Hopefully this helps somebody else that may stray upon this, I’ve attached my logs and packages if anybody else wants to take a more detailed look. It was so weird because the record function litterly worked the night prior and nobody else touched the workstation, so maybe my PC did some sort of weird `apt autoupdate` that made incorrect versions.

### Extra Logs

> **lerobot-find-cameras output (yes, IK the size & FPS is different in this one)**
>
> ioctl(VIDIOC\_QBUF): Bad file descriptor  
> [video4linux2,v4l2 @ 0x5f4ad1cd77c0] ioctl(VIDIOC\_G\_INPUT): Inappropriate ioctl for device  
> ioctl(VIDIOC\_QBUF): Bad file descriptor  
> [video4linux2,v4l2 @ 0x5f4ad1ce1400] ioctl(VIDIOC\_G\_INPUT): Inappropriate ioctl for device
> 
> ## — Detected Cameras — Camera #0: Name: OpenCV Camera @ /dev/video0 Type: OpenCV Id: /dev/video0 Backend api: FFMPEG Default stream profile: Format: 0.0 Fourcc: Width: 1920 Height: 1080 Fps: 5.0
> 
> ## Camera #1: Name: OpenCV Camera @ /dev/video2 Type: OpenCV Id: /dev/video2 Backend api: FFMPEG Default stream profile: Format: 0.0 Fourcc: Width: 1920 Height: 1080 Fps: 5.0

> **Web Camera Info**
>
> ```auto
> ioctl: VIDIOC_ENUM_FMT
> Type: Video Capture
> 
> [0]: 'MJPG' (Motion-JPEG, compressed)
> Size: Discrete 1920x1080
> Interval: Discrete 0.033s (30.000 fps)
> Size: Discrete 800x600
> Interval: Discrete 0.033s (30.000 fps)
> Size: Discrete 640x480
> Interval: Discrete 0.033s (30.000 fps)
> Size: Discrete 640x360
> Interval: Discrete 0.033s (30.000 fps)
> Size: Discrete 1280x720
> Interval: Discrete 0.033s (30.000 fps)
> [1]: 'YUYV' (YUYV 4:2:2)
> Size: Discrete 1280x720
> Interval: Discrete 0.100s (10.000 fps)
> Size: Discrete 800x600
> Interval: Discrete 0.050s (20.000 fps)
> Size: Discrete 640x480
> Interval: Discrete 0.033s (30.000 fps)
> Size: Discrete 640x360
> Interval: Discrete 0.033s (30.000 fps)
> Size: Discrete 1920x1080
> Interval: Discrete 0.200s (5.000 fps)
> 
> ```

> **Packages**
>
> ```auto
> # Name Version Build Channel
> _libgcc_mutex 0.1 main
> _openmp_mutex 5.1 1_gnu
> accelerate 1.12.0 pypi_0 pypi
> aiohappyeyeballs 2.6.1 pypi_0 pypi
> aiohttp 3.13.3 pypi_0 pypi
> aiosignal 1.4.0 pypi_0 pypi
> alsa-lib 1.2.15.3 hb03c661_0 conda-forge
> annotated-types 0.7.0 pypi_0 pypi
> aom 3.9.1 hac33072_0 conda-forge
> async-timeout 5.0.1 pypi_0 pypi
> attr 2.5.2 h39aace5_0 conda-forge
> attrs 25.4.0 pypi_0 pypi
> av 15.1.0 pypi_0 pypi
> bzip2 1.0.8 h5eee18b_6
> ca-certificates 2026.1.4 hbd8a1cb_0 conda-forge
> cairo 1.18.4 h44eff21_0
> certifi 2026.1.4 pypi_0 pypi
> charset-normalizer 3.4.4 pypi_0 pypi
> click 8.3.1 pypi_0 pypi
> cloudpickle 3.1.2 pypi_0 pypi
> cmake 4.1.3 pypi_0 pypi
> datasets 4.1.1 pypi_0 pypi
> dav1d 1.2.1 hd590300_0 conda-forge
> dbus 1.16.2 h24cb091_1 conda-forge
> deepdiff 8.6.1 pypi_0 pypi
> diffusers 0.35.2 pypi_0 pypi
> dill 0.4.0 pypi_0 pypi
> draccus 0.10.0 pypi_0 pypi
> einops 0.8.1 pypi_0 pypi
> evdev 1.9.2 pypi_0 pypi
> expat 2.7.3 h7354ed3_4
> farama-notifications 0.0.4 pypi_0 pypi
> feetech-servo-sdk 1.0.0 pypi_0 pypi
> ffmpeg 7.1.1 gpl_h817a628_111 conda-forge
> filelock 3.20.3 pypi_0 pypi
> font-ttf-dejavu-sans-mono 2.37 hab24e00_0 conda-forge
> font-ttf-inconsolata 3.000 h77eed37_0 conda-forge
> font-ttf-source-code-pro 2.038 h77eed37_0 conda-forge
> font-ttf-ubuntu 0.83 h77eed37_3 conda-forge
> fontconfig 2.15.0 h7e30c49_1 conda-forge
> fonts-conda-ecosystem 1 0 conda-forge
> fonts-conda-forge 1 hc364b38_1 conda-forge
> freetype 2.14.1 ha770c72_0 conda-forge
> fribidi 1.0.16 hb03c661_0 conda-forge
> frozenlist 1.8.0 pypi_0 pypi
> fsspec 2025.9.0 pypi_0 pypi
> gdk-pixbuf 2.44.5 h2b0a6b4_0 conda-forge
> gitdb 4.0.12 pypi_0 pypi
> gitpython 3.1.46 pypi_0 pypi
> gmp 6.3.0 hac33072_2 conda-forge
> graphite2 1.3.14 hecca717_2 conda-forge
> gymnasium 1.2.3 pypi_0 pypi
> harfbuzz 12.3.2 h6083320_0 conda-forge
> hf-transfer 0.1.9 pypi_0 pypi
> hf-xet 1.2.0 pypi_0 pypi
> huggingface-hub 0.35.3 pypi_0 pypi
> icu 78.2 h33c6efd_0 conda-forge
> idna 3.11 pypi_0 pypi
> imageio 2.37.2 pypi_0 pypi
> imageio-ffmpeg 0.6.0 pypi_0 pypi
> importlib-metadata 8.7.1 pypi_0 pypi
> inquirerpy 0.3.4 pypi_0 pypi
> intel-gmmlib 22.9.0 hb700be7_0 conda-forge
> intel-media-driver 25.3.4 hecca717_0 conda-forge
> jinja2 3.1.6 pypi_0 pypi
> jsonlines 4.0.0 pypi_0 pypi
> lame 3.100 h166bdaf_1003 conda-forge
> ld_impl_linux-64 2.44 h153f514_2
> lerc 4.0.0 h0aef613_1 conda-forge
> lerobot 0.4.2 pypi_0 pypi
> level-zero 1.27.0 hb700be7_0 conda-forge
> libabseil 20250512.1 cxx17_hba17884_0 conda-forge
> libass 0.17.4 h96ad9f0_0 conda-forge
> libcap 2.77 h3ff7636_0 conda-forge
> libdeflate 1.25 h17f619e_0 conda-forge
> libdrm 2.4.125 hb03c661_1 conda-forge
> libegl 1.7.0 ha4b6fd6_2 conda-forge
> libexpat 2.7.3 h7354ed3_4
> libffi 3.4.4 h6a678d5_1
> libflac 1.5.0 he200343_1 conda-forge
> libfreetype 2.14.1 ha770c72_0 conda-forge
> libfreetype6 2.14.1 h73754d4_0 conda-forge
> libgcc 15.2.0 h69a1729_7
> libgcc-ng 15.2.0 h166f726_7
> libgl 1.7.0 ha4b6fd6_2 conda-forge
> libglib 2.86.3 h8b17d9a_0
> libglvnd 1.7.0 ha4b6fd6_2 conda-forge
> libglx 1.7.0 ha4b6fd6_2 conda-forge
> libgomp 15.2.0 h4751f2c_7
> libhwloc 2.12.2 default_hafda6a7_1000 conda-forge
> libiconv 1.18 h3b78370_2 conda-forge
> libjpeg-turbo 3.1.2 hb03c661_0 conda-forge
> liblzma 5.8.2 hb03c661_0 conda-forge
> liblzma-devel 5.8.2 hb03c661_0 conda-forge
> libnsl 2.0.0 h5eee18b_0
> libogg 1.3.5 hd0c01bc_1 conda-forge
> libopenvino 2025.2.0 hb617929_1 conda-forge
> libopenvino-auto-batch-plugin 2025.2.0 hed573e4_1 conda-forge
> libopenvino-auto-plugin 2025.2.0 hed573e4_1 conda-forge
> libopenvino-hetero-plugin 2025.2.0 hd41364c_1 conda-forge
> libopenvino-intel-cpu-plugin 2025.2.0 hb617929_1 conda-forge
> libopenvino-intel-gpu-plugin 2025.2.0 hb617929_1 conda-forge
> libopenvino-intel-npu-plugin 2025.2.0 hb617929_1 conda-forge
> libopenvino-ir-frontend 2025.2.0 hd41364c_1 conda-forge
> libopenvino-onnx-frontend 2025.2.0 h1862bb8_1 conda-forge
> libopenvino-paddle-frontend 2025.2.0 h1862bb8_1 conda-forge
> libopenvino-pytorch-frontend 2025.2.0 hecca717_1 conda-forge
> libopenvino-tensorflow-frontend 2025.2.0 h0767aad_1 conda-forge
> libopenvino-tensorflow-lite-frontend 2025.2.0 hecca717_1 conda-forge
> libopus 1.6.1 h280c20c_0 conda-forge
> libpciaccess 0.18 hb9d3cd8_0 conda-forge
> libpng 1.6.54 h421ea60_0 conda-forge
> libprotobuf 6.31.1 h49aed37_4 conda-forge
> librsvg 2.60.0 h61e6d4b_0 conda-forge
> libsndfile 1.2.2 hc7d488a_2 conda-forge
> libsqlite 3.51.2 hf4e2dac_0 conda-forge
> libstdcxx 15.2.0 h39759b7_7
> libstdcxx-ng 15.2.0 hc03a8fd_7
> libsystemd0 258.3 h6569c3e_0 conda-forge
> libtiff 4.7.1 h9d88235_1 conda-forge
> libudev1 258.3 h6569c3e_0 conda-forge
> libunwind 1.8.3 h65a8314_0 conda-forge
> liburing 2.13 hb700be7_0 conda-forge
> libusb 1.0.29 h73b1eb8_0 conda-forge
> libuuid 2.41.3 h5347b49_0 conda-forge
> libva 2.23.0 he1eb515_0 conda-forge
> libvorbis 1.3.7 h54a6638_2 conda-forge
> libvpl 2.15.0 h54a6638_1 conda-forge
> libvpx 1.14.1 hac33072_0 conda-forge
> libvulkan-loader 1.4.341.0 h5279c79_0 conda-forge
> libwebp-base 1.6.0 hd42ef1d_0 conda-forge
> libxcb 1.17.0 h9b100fa_0
> libxkbcommon 1.13.1 hca5e8e5_0 conda-forge
> libxml2 2.15.1 he237659_1 conda-forge
> libxml2-16 2.15.1 hca6bf5a_1 conda-forge
> libzlib 1.3.1 hb25bd0a_0
> markupsafe 3.0.3 pypi_0 pypi
> mergedeep 1.3.4 pypi_0 pypi
> mpg123 1.32.9 hc50e24c_0 conda-forge
> mpmath 1.3.0 pypi_0 pypi
> multidict 6.7.0 pypi_0 pypi
> multiprocess 0.70.16 pypi_0 pypi
> mypy-extensions 1.1.0 pypi_0 pypi
> ncurses 6.5 h7934f7d_0
> networkx 3.4.2 pypi_0 pypi
> numpy 2.2.6 pypi_0 pypi
> nvidia-cublas-cu12 12.6.4.1 pypi_0 pypi
> nvidia-cuda-cupti-cu12 12.6.80 pypi_0 pypi
> nvidia-cuda-nvrtc-cu12 12.6.77 pypi_0 pypi
> nvidia-cuda-runtime-cu12 12.6.77 pypi_0 pypi
> nvidia-cudnn-cu12 9.5.1.17 pypi_0 pypi
> nvidia-cufft-cu12 11.3.0.4 pypi_0 pypi
> nvidia-cufile-cu12 1.11.1.6 pypi_0 pypi
> nvidia-curand-cu12 10.3.7.77 pypi_0 pypi
> nvidia-cusolver-cu12 11.7.1.2 pypi_0 pypi
> nvidia-cusparse-cu12 12.5.4.2 pypi_0 pypi
> nvidia-cusparselt-cu12 0.6.3 pypi_0 pypi
> nvidia-nccl-cu12 2.26.2 pypi_0 pypi
> nvidia-nvjitlink-cu12 12.6.85 pypi_0 pypi
> nvidia-nvtx-cu12 12.6.77 pypi_0 pypi
> ocl-icd 2.3.3 hb9d3cd8_0 conda-forge
> opencl-headers 2025.06.13 h5888daf_0 conda-forge
> opencv-python 4.13.0.90 pypi_0 pypi
> opencv-python-headless 4.12.0.88 pypi_0 pypi
> openh264 2.6.0 hc22cd8d_0 conda-forge
> openssl 3.6.1 h35e630c_1 conda-forge
> orderly-set 5.5.0 pypi_0 pypi
> packaging 25.0 pypi_0 pypi
> pandas 2.3.3 pypi_0 pypi
> pango 1.56.4 hadf4263_0 conda-forge
> pcre2 10.46 h1321c63_0 conda-forge
> pfzy 0.3.4 pypi_0 pypi
> physical-ai-interpretability 0.1.4 pypi_0 pypi
> pillow 12.1.0 pypi_0 pypi
> pip 25.3 pyhc872135_0
> pixman 0.46.4 h54a6638_1 conda-forge
> platformdirs 4.5.1 pypi_0 pypi
> prompt-toolkit 3.0.52 pypi_0 pypi
> propcache 0.4.1 pypi_0 pypi
> protobuf 6.33.4 pypi_0 pypi
> psutil 7.2.1 pypi_0 pypi
> pthread-stubs 0.3 h0ce48e5_1
> pugixml 1.15 h3f63f65_0 conda-forge
> pulseaudio-client 17.0 h9a6aba3_3 conda-forge
> pyarrow 23.0.0 pypi_0 pypi
> pydantic 2.12.5 pypi_0 pypi
> pydantic-core 2.41.5 pypi_0 pypi
> pynput 1.8.1 pypi_0 pypi
> pyserial 3.5 pypi_0 pypi
> python 3.10.12 hd12c33a_0_cpython conda-forge
> python-dateutil 2.9.0.post0 pypi_0 pypi
> python-xlib 0.33 pypi_0 pypi
> pytz 2025.2 pypi_0 pypi
> pyyaml 6.0.3 pypi_0 pypi
> pyyaml-include 1.4.1 pypi_0 pypi
> readline 8.3 hc2a1206_0
> regex 2026.1.15 pypi_0 pypi
> requests 2.32.5 pypi_0 pypi
> rerun-sdk 0.26.2 pypi_0 pypi
> robocandywrapper 0.2.4 pypi_0 pypi
> safetensors 0.7.0 pypi_0 pypi
> scipy 1.15.3 pypi_0 pypi
> sdl2 2.32.56 h54a6638_0 conda-forge
> sdl3 3.2.30 h3b84278_0 conda-forge
> sentry-sdk 2.50.0 pypi_0 pypi
> setuptools 80.9.0 py310h06a4308_0
> six 1.17.0 pypi_0 pypi
> smmap 5.0.2 pypi_0 pypi
> snappy 1.2.2 h03e3b7b_1 conda-forge
> sqlite 3.51.1 he0a8d7e_0
> svt-av1 3.1.2 hecca717_0 conda-forge
> sympy 1.14.0 pypi_0 pypi
> tbb 2022.3.0 hb700be7_2 conda-forge
> termcolor 3.3.0 pypi_0 pypi
> tk 8.6.15 h54e0aa7_0
> toml 0.10.2 pypi_0 pypi
> torch 2.7.1 pypi_0 pypi
> torchcodec 0.5 pypi_0 pypi
> torchvision 0.22.1 pypi_0 pypi
> tqdm 4.67.1 pypi_0 pypi
> triton 3.3.1 pypi_0 pypi
> typing-extensions 4.15.0 pypi_0 pypi
> typing-inspect 0.9.0 pypi_0 pypi
> typing-inspection 0.4.2 pypi_0 pypi
> tzdata 2025.3 pypi_0 pypi
> urllib3 2.6.3 pypi_0 pypi
> wandb 0.21.4 pypi_0 pypi
> wayland 1.24.0 hdac8c69_0
> wayland-protocols 1.47 hd8ed1ab_0 conda-forge
> wcwidth 0.3.1 pypi_0 pypi
> wheel 0.45.1 py310h06a4308_0
> x264 1!164.3095 h166bdaf_2 conda-forge
> x265 3.5 h924138e_3 conda-forge
> xkeyboard-config 2.46 hb03c661_0 conda-forge
> xorg-libx11 1.8.12 h9b100fa_1
> xorg-libxau 1.0.12 h9b100fa_0
> xorg-libxcursor 1.2.3 hb9d3cd8_0 conda-forge
> xorg-libxdmcp 1.1.5 h9b100fa_0
> xorg-libxext 1.3.6 hb9d3cd8_0 conda-forge
> xorg-libxfixes 6.0.2 hb03c661_0 conda-forge
> xorg-libxrandr 1.5.5 hb03c661_0 conda-forge
> xorg-libxrender 0.9.12 hb9d3cd8_0 conda-forge
> xorg-libxscrnsaver 1.2.4 hb9d3cd8_0 conda-forge
> xorg-xorgproto 2024.1 h5eee18b_1
> xxhash 3.6.0 pypi_0 pypi
> xz 5.8.2 ha02ee65_0 conda-forge
> xz-gpl-tools 5.8.2 ha02ee65_0 conda-forge
> xz-tools 5.8.2 hb03c661_0 conda-forge
> yarl 1.22.0 pypi_0 pypi
> zipp 3.23.0 pypi_0 pypi
> zlib 1.3.1 hb25bd0a_0
> zstd 1.5.7 hb78ec9c_6 conda-forge
> 
> ```

> **lerobot-record output**
>
> ```auto
> WARNING:lerobot.cameras.opencv.camera_opencv:OpenCVCamera(/dev/video0) failed to set fourcc=MJPG (actual=, success=False). Continuing with default format.
> Traceback (most recent call last):
> File "/home/enee-467-4/Documents/lerobot_ws/record_dataset.py", line 66, in <module>
> follower.connect()
> File "/home/enee-467-4/miniforge3/envs/lerobot/lib/python3.10/site-packages/lerobot/robots/so101_follower/so101_follower.py", line 101, in connect
> cam.connect()
> File "/home/enee-467-4/miniforge3/envs/lerobot/lib/python3.10/site-packages/lerobot/cameras/opencv/camera_opencv.py", line 172, in connect
> self._configure_capture_settings()
> File "/home/enee-467-4/miniforge3/envs/lerobot/lib/python3.10/site-packages/lerobot/cameras/opencv/camera_opencv.py", line 221, in _configure_capture_settings
> self._validate_width_and_height()
> File "/home/enee-467-4/miniforge3/envs/lerobot/lib/python3.10/site-packages/lerobot/cameras/opencv/camera_opencv.py", line 278, in _validate_width_and_height
> raise RuntimeError(
> RuntimeError: OpenCVCamera(/dev/video0) failed to set capture_width=640 (actual_width=640, width_success=False).
> ioctl(VIDIOC_QBUF): Bad file descriptor
> 
> ```

---

<div class="post-metadata">

**Author:** ![lmbsh](https://avatars.discourse-cdn.com/v4/letter/l/a587f6/32.png) [@lmbsh](https://discuss.huggingface.co/u/lmbsh)\
**Post date:** [February 20, 2026, 5:50pm UTC](https://discuss.huggingface.co/t/lerobot-camera-backend-issues/173200/2 "2026-02-20T17:50:02Z")

</div>

Hi,

can you check your OpenCV dependencies?  
I experienced the same issue and found my virtual environment had different versions of opencv installed (because of dependencies from other packages I use):

```auto
opencv-contrib-python==4.13.0.92
opencv-python==4.11.0.86
opencv-python-headless==4.12.0.88

```

After pinning all opencv dependencies to `4.12.0.88` I don’t encounter your described error anymore.

It feels wrong to have different opencv dependencies in one project, but I am a novice myself and don’t know exactly the reason for this.

Good luck