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The purpose of this page is to publish preliminary results and questions. The content is entirely temporary and subject to change. Links to this page are useless except for brief discussions. Items will be removed when resolved.

How to retrieve an MJPG stream from an EMEET S600 USB webcam?

$ v4l2-ctl --list-devices
EMEET SmartCam S600: EMEET Smar (usb-0000:6f:00.4-2.3.3):
	/dev/video0
	/dev/video1
	/dev/media0
$ v4l2-ctl --list-formats-ext
ioctl: VIDIOC_ENUM_FMT
...
	[0]: 'MJPG' (Motion-JPEG, compressed)
		Size: Discrete 3840x2160
			Interval: Discrete 0.033s (30.000 fps)
etc...
...
	[1]: 'YUYV' (YUYV 4:2:2)
		Size: Discrete 640x480
			Interval: Discrete 0.033s (30.000 fps)
		Size: Discrete 640x360
			Interval: Discrete 0.033s (30.000 fps)

So YUYV is limited where MJPG offers high resolutions. This is where quite some programs fail by using YUYV only. Like this:

$ ffmpeg -f v4l2 -i /dev/v4l/by-path/pci-0000:6f:00.4-usb-0:2.3.3:1.0-video-index0 test.mp4
...
[video4linux2,v4l2 @ 0x5584e52d95c0] The V4L2 driver changed the video from 1920x1080 to 640x480
...
Stream #0:0: Video: rawvideo (YUY2 / 0x32595559), yuyv422, 640x480, 147456 kb/s, 30 fps, 30 tbr, 1000k tbn
...

This page offers examples of how to retrieve information and do settings. Unfortunately it doesn’t cover choosing between MJPG and YUYV.

The following statements are interesting because the output is exactly the same:

$ ffmpeg -f v4l2 -list_formats all -i /dev/video0
$ ffmpeg -list_formats all -i /dev/video0

result both is:

...
... Compressed: mjpeg : Motion-JPEG : 3840x2160 2560x1440 1920x1080 1280x960 1280x720 1024x576 960x720 800x600 640x480 640x360
...Raw : yuyv422 : YUYV 4:2:2 : 640x480 640x360

This post reflects on choosing different inputs:

ffmpeg -f v4l2 -input_format mjpeg -framerate 30 -video_size 3840x2160 -i /dev/video0 -c:v copy test.mp4

How to use a USB webcam as a rear-view mirror on your Android phone?

The easy answer to this question: connect a proper USB cable and install a viewer such as “USB Camera Viewer”.

Then there are complications of course.

  • The cable length can be a show stopper.
  • The camera drains the battery during longer trips.
  • So the questions are:
    • How can the cable go beyond USB limitations?
    • Is it possible to inject power to the cable?

What are the best 8″ – 10″ monitors?

Small monitors that can serve as a rear-view mirror are few and far between. The best I could find was a ‘Jonsbo DS8’ 8-inch LCD monitor. In terms of OLED, there is nothing to be found in this size. The idea arose to use an OLED phone, dedicated or otherwise, to display the RTSP stream from the rear camera.

A Google Pixel 6 Pro has a screen diagonal of 6.7 inches and barely obstructs the view. In that case, the question becomes how to forward an RTSP stream coming in on a Linux system to the phone.

Two approaches that get close…

https://superuser.com/questions/361130/how-to-stream-the-pc-desktop-to-a-phone-with-vlc

https://android.stackexchange.com/questions/7034/can-i-stream-video-from-pc-to-an-android-device-over-usb

More… https://prime-5.videolan.me/vlc-user/streaming_files/en/advanced/streaming/rtsp_session.html

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