Comment puis-je répertorier les modes vidéo disponibles pour une webcam USB sous Linux ?

Si vous avez v4l (video 4 linux 2) installé vous pouvez faire :

v4l2-ctl --list-formats

La réponse acceptée (v4l2-ctl --list-formats ) semble n'afficher que le premier format disponible, par exemple :

$ v4l2-ctl --list-formats
ioctl: VIDIOC_ENUM_FMT
        Index       : 0
        Type        : Video Capture
        Pixel Format: ''
        Name        : 2036315a-0000-0010-8000-00aa003

        Index       : 1
        Type        : Video Capture
        Pixel Format: ''
        Name        : 00000050-0000-0010-8000-00aa003

Pour voir tout formats disponibles, vous pouvez utiliser un script semblable à celui-ci :

$ for d in /dev/video* ; do echo $d ; v4l2-ctl --device=$d -D --list-formats  ; echo '===============' ; done
/dev/video0
Driver Info (not using libv4l2):
        Driver name   : uvcvideo
        Card type     : Intel(R) RealSense(TM) 410
        Bus info      : usb-0000:00:14.0-1
        Driver version: 4.4.13
        Capabilities  : 0x84200001
                Video Capture
                Streaming
                Extended Pix Format
                Device Capabilities
        Device Caps   : 0x04200001
                Video Capture
                Streaming
                Extended Pix Format
ioctl: VIDIOC_ENUM_FMT
        Index       : 0
        Type        : Video Capture
        Pixel Format: 'Z16 '
        Name        : Depth data 16-bit (Z16)

        Index       : 1
        Type        : Video Capture
        Pixel Format: ''
        Name        : 00000050-0000-0010-8000-00aa003

===============
/dev/video1
Driver Info (not using libv4l2):
        Driver name   : uvcvideo
        Card type     : Intel(R) RealSense(TM) 410
        Bus info      : usb-0000:00:14.0-1
        Driver version: 4.4.13
        Capabilities  : 0x84200001
                Video Capture
                Streaming
                Extended Pix Format
                Device Capabilities
        Device Caps   : 0x04200001
                Video Capture
                Streaming
                Extended Pix Format
ioctl: VIDIOC_ENUM_FMT
        Index       : 0
        Type        : Video Capture
        Pixel Format: ''
        Name        : 00000032-0000-0010-8000-00aa003

        Index       : 1
        Type        : Video Capture
        Pixel Format: 'UYVY'
        Name        : UYVY 4:2:2

        Index       : 2
        Type        : Video Capture
        Pixel Format: 'Y8I '
        Name        : Greyscale 8 L/R (Y8I)

        Index       : 3
        Type        : Video Capture
        Pixel Format: 'Y12I'
        Name        : Greyscale 12 L/R (Y12I)

===============
$ v4l2-ctl -D -d /dev/video1 --list-formats-ext
Driver Info (not using libv4l2):
        Driver name   : uvcvideo
        Card type     : Intel(R) RealSense(TM) 410
        Bus info      : usb-0000:00:14.0-1
        Driver version: 4.4.13
        Capabilities  : 0x84200001
                Video Capture
                Streaming
                Extended Pix Format
                Device Capabilities
        Device Caps   : 0x04200001
                Video Capture
                Streaming
                Extended Pix Format
ioctl: VIDIOC_ENUM_FMT
        Index       : 0
        Type        : Video Capture
        Pixel Format: ''
        Name        : 00000032-0000-0010-8000-00aa003
                Size: Discrete 424x240
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 480x270
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 640x360
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 640x480
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 848x480
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 1280x720
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)

        Index       : 1
        Type        : Video Capture
        Pixel Format: 'UYVY'
        Name        : UYVY 4:2:2
                Size: Discrete 424x240
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 480x270
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 640x360
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 640x480
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 848x480
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 1280x720
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)

        Index       : 2
        Type        : Video Capture
        Pixel Format: 'Y8I '
        Name        : Greyscale 8 L/R (Y8I)
                Size: Discrete 424x240
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 480x270
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 640x360
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 640x480
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 848x480
                        Interval: Discrete 0.011s (90.000 fps)
                        Interval: Discrete 0.017s (60.000 fps)
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 1280x720
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                        Interval: Discrete 0.167s (6.000 fps)
                Size: Discrete 1920x1080
                        Interval: Discrete 0.033s (30.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)

        Index       : 3
        Type        : Video Capture
        Pixel Format: 'Y12I'
        Name        : Greyscale 12 L/R (Y12I)
                Size: Discrete 960x540
                        Interval: Discrete 0.040s (25.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)
                Size: Discrete 1920x1080
                        Interval: Discrete 0.040s (25.000 fps)
                        Interval: Discrete 0.067s (15.000 fps)

Si vous utilisez des contrôles uvc pour une webcam, une autre méthode est :

uvcdynctrl -f

Vous pouvez aussi faire :

uvcdynctrl -l

pour lister tous les appareils.