Raspberry Camera API

Latest revision as of 15:49, 4 January 2022

Back to Robobot

[edit] Camera use

Raspberry pi operating system version "bullseye" uses a new camera library.

The info is taken from https://www.raspberrypi.com/documentation/accessories/camera.html#libcamera-and-libcamera-apps?ref=https://githubhelp.com

[edit] LibCamera

If not already installed, install with

sudo apt install libcamera-apps

It should not be needed to install libcamera-dev

[edit] Camera streaming

The libcamera library can do streaming out of the box with the command:

libcamera-vid -n -t 0 --inline --listen --rotation 0 --framerate 30 --width 1920 --height 1080 -o tcp://0.0.0.0:8888

It will listen to port 8888 for TCP connections on the localhost.

From another PC the stream can be displayed by VLC, (or the same parameter in the VLC "media" -> "open network stream")

vlc tcp/h264://192.168.2.14:8888

if 192.168.2.14 is the IP of the Raspberry pi. The streaming will terminate when the VLC stops the connection.

A start-script is placed in the "local" home folder.

./stream_cam.sh

with examples of different solutions.

[edit] camera from OpenCV

The raspberry cameras seem to prefer 10 bit/pixel in Bayer RGGB format - other formats are not consistent for both new and old camera.

[edit] Format check

Install package v4l-utils (also installed by default)

sudo apt install v4l-utils

The supported image formats from both cameras are:

v4l2-ctl -d/dev/video0 --list-formats

ioctl: VIDIOC_ENUM_FMT
       Type: Video Capture
       [0]: 'BA81' (8-bit Bayer BGBG/GRGR)
       [1]: 'pBAA' (10-bit Bayer BGBG/GRGR Packed)
       [2]: 'BG10' (10-bit Bayer BGBG/GRGR)

For the used format 'BG10' the frame sizes supported is found

v4l2-ctl -d /dev/video0 --list-framesizes BG10

ioctl: VIDIOC_ENUM_FRAMESIZES
       Size: Discrete 2592x1944
       Size: Discrete 1920x1080
       Size: Discrete 1296x972
       Size: Discrete 640x480

But formats can be converted to other formats, visible as other video devices e.g /dev/video12.

v4l2-ctl -d/dev/video12 --list-formats

ioctl: VIDIOC_ENUM_FMT
       Type: Video Capture Multiplanar
       [0]: 'YUYV' (YUYV 4:2:2)
       [1]: 'YVYU' (YVYU 4:2:2)
       [2]: 'VYUY' (VYUY 4:2:2)
       [3]: 'UYVY' (UYVY 4:2:2)
       [4]: 'YU12' (Planar YUV 4:2:0)
       [5]: 'YV12' (Planar YVU 4:2:0)
       [6]: 'RGB3' (24-bit RGB 8-8-8)
       [7]: 'BGR3' (24-bit BGR 8-8-8)
       [8]: 'BGR4' (32-bit BGRA/X 8-8-8-8)
       [9]: 'RGBP' (16-bit RGB 5-6-5)
       [10]: 'NV12' (Y/CbCr 4:2:0)
       [11]: 'NV21' (Y/CrCb 4:2:0)

Format BA81 did not give a proper result for both cameras. I didn't succeed in using the converted formats, maybe because they are based on the BA81 format. Format 'BG10' works for both cameras and is easily converted to RGB format using OpenCV (https://docs.opencv.org/3.4/db/d64/tutorial_js_colorspaces.html).