この記事で使用したWebcamはLogicoolのC270
#Webcamで設定可能な解像度やフレームレートを調べる方法
準備
$ sudo apt install v4l-utils
v4l2-ctl --list-formats-ext を使う。
この解像度とフレームレートの組み合わせだとWebcamから取得した後で変換しなくてすむ。
$ v4l2-ctl --list-formats-ext
ioctl: VIDIOC_ENUM_FMT
Index : 0
Type : Video Capture
Pixel Format: 'YUYV'
Name : YUYV 4:2:2
Size: Discrete 640x480
Interval: Discrete 0.033s (30.000 fps)
Interval: Discrete 0.040s (25.000 fps)
Interval: Discrete 0.050s (20.000 fps)
Interval: Discrete 0.067s (15.000 fps)
Interval: Discrete 0.100s (10.000 fps)
Interval: Discrete 0.200s (5.000 fps)
Size: Discrete 160x120
Interval: Discrete 0.033s (30.000 fps)
Interval: Discrete 0.040s (25.000 fps)
Interval: Discrete 0.050s (20.000 fps)
Interval: Discrete 0.067s (15.000 fps)
Interval: Discrete 0.100s (10.000 fps)
Interval: Discrete 0.200s (5.000 fps)
Size: Discrete 176x144
Interval: Discrete 0.033s (30.000 fps)
Interval: Discrete 0.040s (25.000 fps)
Interval: Discrete 0.050s (20.000 fps)
Interval: Discrete 0.067s (15.000 fps)
Interval: Discrete 0.100s (10.000 fps)
Interval: Discrete 0.200s (5.000 fps)
Size: Discrete 320x176
Interval: Discrete 0.033s (30.000 fps)
Interval: Discrete 0.040s (25.000 fps)
Interval: Discrete 0.050s (20.000 fps)
Interval: Discrete 0.067s (15.000 fps)
Interval: Discrete 0.100s (10.000 fps)
Interval: Discrete 0.200s (5.000 fps)
...
長いのでgistに貼りました。
https://gist.github.com/tetsu-koba/175c956fcc2abe7be925ca47a9aac4bc
#Webcamに設定可能な項目
$ v4l2-ctl --all
Driver Info (not using libv4l2):
Driver name : uvcvideo
Card type : UVC Camera (046d:0825)
Bus info : usb-3f980000.usb-1.5
Driver version: 4.14.24
Capabilities : 0x84200001
Video Capture
Streaming
Extended Pix Format
Device Capabilities
Device Caps : 0x04200001
Video Capture
Streaming
Extended Pix Format
Priority: 2
Video input : 0 (Camera 1: ok)
Format Video Capture:
Width/Height : 640/480
Pixel Format : 'YUYV'
Field : None
Bytes per Line : 1280
Size Image : 614400
Colorspace : sRGB
Transfer Function : Default
YCbCr/HSV Encoding: Default
Quantization : Default
Flags :
Crop Capability Video Capture:
Bounds : Left 0, Top 0, Width 640, Height 480
Default : Left 0, Top 0, Width 640, Height 480
Pixel Aspect: 1/1
Selection: crop_default, Left 0, Top 0, Width 640, Height 480
Selection: crop_bounds, Left 0, Top 0, Width 640, Height 480
Streaming Parameters Video Capture:
Capabilities : timeperframe
Frames per second: 30.000 (30/1)
Read buffers : 0
brightness (int) : min=0 max=255 step=1 default=-8193 value=128
contrast (int) : min=0 max=255 step=1 default=57343 value=32
saturation (int) : min=0 max=255 step=1 default=57343 value=32
white_balance_temperature_auto (bool) : default=1 value=1
gain (int) : min=0 max=255 step=1 default=57343 value=64
power_line_frequency (menu) : min=0 max=2 default=2 value=2
white_balance_temperature (int) : min=0 max=10000 step=10 default=61432 value=4000 flags=inactive
sharpness (int) : min=0 max=255 step=1 default=57343 value=24
backlight_compensation (int) : min=0 max=1 step=1 default=57343 value=0
exposure_auto (menu) : min=0 max=3 default=0 value=3
exposure_absolute (int) : min=1 max=10000 step=1 default=166 value=166 flags=inactive
exposure_auto_priority (bool) : default=0 value=1
#ffmpegから設定可能な解像度の一覧
$ ffmpeg -f v4l2 -list_formats all -i /dev/video0
ffmpeg version 3.2.10-1~deb9u1+rpt1 Copyright (c) 2000-2018 the FFmpeg developers
built with gcc 6.3.0 (Raspbian 6.3.0-18+rpi1) 20170516
configuration: --prefix=/usr --extra-version='1~deb9u1+rpt1'
(... omit ...)
[video4linux2,v4l2 @ 0x11505c0] Raw : yuyv422 : YUYV 4:2:2 : 640x480 160x120 176x144 320x176 320x240 352x288 432x240 544x288 640x360 752x416 800x448 800x600 864x480 960x544 960x720 1024x576 1184x656 1280x720 1280x960
[video4linux2,v4l2 @ 0x11505c0] Compressed: mjpeg : Motion-JPEG : 640x480 160x120 176x144 320x176 320x240 352x288 432x240 544x288 640x360 752x416 800x448 800x600 864x480 960x544 960x720 1024x576 1184x656 1280x720 1280x960
/dev/video0: Immediate exit requested
（横スクロールして見てください)
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