MJPG output from webcam (MATLAB Support Package for USB Webcams)

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SG 2019-4-9

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https://ww2.mathworks.cn/matlabcentral/answers/455300-mjpg-output-from-webcam-matlab-support-package-for-usb-webcams

编辑： Jerico 2023-2-7

Is it somehow possible to acquire images in MJPG instead of YUV format with the snapshot function?

I need a higher framerate from my webcam. According to the datasheet YUV is 5 fps@1600x1200 while MJPG is 15 fps@1600x1200.

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William Thielicke 2021-11-2

I have the exact same question.

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yanqi liu 2021-11-5

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https://ww2.mathworks.cn/matlabcentral/answers/455300-mjpg-output-from-webcam-matlab-support-package-for-usb-webcams#answer_824169

sir，i think may be consider the camera device config

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William Thielicke 2021-11-5

在 MATLAB Online 中打开

Ok, it sems that this is not 100% Matlab related.... Still, it is very unclear to me how I can change the mode of the webcam and set it to YUYV422 or MJPEG.

I am playing around with ffmpeg, I can e.g. set the following:

ffmpeg -f dshow -pixel_format yuyv422 -show_video_device_dialog true -i video="OPTOLUTION_USB_Cam1"

Then I get (amonst other stuff I dont fully understand) the following reply from ffmpeg:

Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 1600x1200, 5 fps, 5 tbr, 10000k tbn, 10000k tbc

I can also set something else with ffmpeg:

ffmpeg -f dshow -vcodec mjpeg -show_video_device_dialog true -i video="OPTOLUTION_USB_Cam1"

... then the reply is:

Stream #0:0: Video: mjpeg (Baseline) (MJPG / 0x47504A4D), yuvj422p(pc, bt470bg/unknown/unknown), 1600x1200, 30 fps, 30 tbr, 10000k tbn, 10000k tbc

So, apparently this somehow affects the setting of the webcam. But this still doesn't seem to have an effect inside Matlab. However, I think that I "accidentally" managed to run my Webcam in Matlab using MJPEG a single time (because it had like 50 fps in the preview video). But I cannot reproduce this... Any ideas?

William Thielicke 2021-11-6

I just copied the text from MATLAB help to show what options exist in general. I am pretty sure that it doesn't matter what camera I use. MATLAB just silently changed the way it handles webcams, there seems to be no changelog available. So I am totally stuck and can't continue developing hardware for people that use my toolbox. This is pretty frustrating.... I am using this camera: https://www.arducam.com/product/arducam-2mp-global-shutter-usb-camera-board-for-computer-50fps-ov2311-monochrome-uvc-webcam-module-with-low-distortion-m12-lens-without-microphones-compatible-with-windows-linux-android-and-mac-os/

And it is super important to know of MJPEG or another format is used (I absolutely prefer non compressed data), because I am triggering the camera. The timing between hardware Trigger input and the actual exposure needs to be known exactly for my application. And this timing is totally different between MJPEG and other formats. So in the end, I think I have to use ffmpeg (called from my MATLAB GUI) to capture the data which really sucks.

William Thielicke 2021-11-6

编辑：William Thielicke 2021-11-6

@yanqi liu: The application is not for me. It is for the users of a popular toolbox. But with a random and apparently undocumented change of MATLABs behaviour, this will be pretty hard.

Jerico 2023-2-7

编辑：Jerico 2023-2-7

Hi has anyone resolved this problem? I'm having the exact problem now. I'm using a logitech brio 4k and I can't seems to be available to load a 4k resolutions due to this problem. thanks in advance

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