Latest version doesn't support MJPEG

[milong26]

I try to use MJPEG in opencv camera setting:

self.camera.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter_fourcc(*'MJPG'))

This works well in 42bf1e8b for in 78fd1a1e04f87f3ec52428f72c29485124472fbc support MJPEG image to video but in 6d723c4 it adds restriction on image format.

Does lerobot require YUYV format?

[CarolinePascal]

Hi @milong26 !

If I understand your issue correctly, you are trying to use the MJPEG encoders instead of the default av1 decoder. Starting from 6d723c4, we decided to restrict the available encoders to the three tested in our video benchmark. You may have a look at the corresponding PR #983 to get more details.

That being said, if you think that MJPEG could be a good alternative to av1 feel free to detail why here !

Best,

Caroline.

[milong26]

Hi @milong26 !

If I understand your issue correctly, you are trying to use the MJPEG encoders instead of the default av1 decoder. Starting from 6d723c4, we decided to restrict the available encoders to the three tested in our video benchmark. You may have a look at the corresponding PR #983 to get more details.

That being said, if you think that MJPEG could be a good alternative to av1 feel free to detail why here !

Best,

Caroline.

Yeah your understanding right. I know that I have to use default av1 decoder if I want to follow video benchmarl :D thanks for your answer.

To me I can just use only these two : YUYV and MJPEG under camera setting. like this

v4l2-ctl -d /dev/video0 --list-formats
ioctl: VIDIOC_ENUM_FMT
        Type: Video Capture

        [0]: 'MJPG' (Motion-JPEG, compressed)
        [1]: 'YUYV' (YUYV 4:2:2)

but when I use default YUYV bandwidth is a problem(cursed). So I have a try on MJPG it woks.
I don't know clearly the real differece between these two format(just mjpeg takes smaller space and gets compressed picture) Will MJPEG format make much difference to the result?

[milong26]

Thanks! I will take MJPEG format as a test, after this I'll tell u how about it going. :)

[vkamenski]

Just adding a data point: I’m using a Logitech C920 on Ubuntu 24.04, and I can confirm that the camera only works reliably with the MJPG format. While YUYV is also listed by v4l2-ctl, it results in severe frame drops or flickering at higher resolutions (e.g., 1280x720). Forcing MJPG via v4l2-ctl or OpenCV's CAP_PROP_FOURCC is the only stable option in my setup.

[CarolinePascal]

Hi @milong26 @vkamenski !

Have you seen PR #1558 ? Please let us now on the PR feed if the proposed MJPG support also solved your issue. This will motivate a faster merge into main ;)

Best,

Caroline.

[forgetwhatuwant]

Hi @vkamenski @milong26 ,
Please feel free to test the PR #1558 , i just use MJPG as my opencv format to run smolvla policy from data-collecting to trainning and inference.
Best wish!