LINUX
Works on Linux using the UVC driver. I must say, I really like how they're now engineering the webcam devices now adays! A universal driver, with the camera electronics providing several stream devices.
DIFFERENCES C922 vs C920
I'm guessing the differences between the C922 and C920, the C922 just provides a faster processor (CPU) for faster frame rates (fps) while lacking a privacy cover. Thinking they're assuming the blue LED light upon camera activation is adequate. Both provide glass lenses, while the C922 also includes a small stand. Likely, instead of other people looking down upon you, they're looking up at you.
LINUX INSTALLATION
Linux Kernel
linux > drivers > Multimedia (media) > USB Video Class (UVC)
If the module/driver hasn't already automagically loaded, then load the driver
# modprobe uvcvideo
Ensure you're using the correct audio record device, mine is hw:0,0 using an additional PCI-E Asus Xonar ST, although you may prefer the webcam's built-in.
$ arecord --list-devices
Ensure you're using the correct video device, mine is /dev/video2, as I have a Hauppauge TV/video capture card.
$ v4l2-ctl --list-devices
Capture some audio/video:
$ ffmpeg -f v4l2 -video_size 640x480 -i /dev/video0 -f alsa -i hw:0,0 -c:v libx264 -preset ultrafast -c:a aac -crf 0 webcam.mp4
Thinking on the whim in conjunction what TV ATSC uses, MPEG TS or PS, are probably the best defacto stream recording methods, easily played, edited or archived,
$ ffmpeg -f v4l2 -i /dev/video2 -f alsa -i hw:0,0 webcam.ts
NVIDIA NvENC H/W ACCELERATION
When trying the maximum resolutions 1080p (1920x1080) or 720p (1280x720), all I get is broken audio/video sync, "Audio/Video desynchronisation detected!" FFMpeg error. See below TODO items. The Windows Logitech Camera Capture software averts the desynchronization by likely using Nvidia's NvEncoder, as I have a Nvidia Geforce 670 video card. Took me awhile, but I now have 1080p/720p stutter free on my Linux box, substitute "-video_size 1920x1080":
$ ffmpeg -f v4l2 -input_format "mjpeg" -video_size 1080x720 -i /dev/video2 -f alsa -i hw:0,0 -pix_fmt yuv420p -acodec aac -c:v h264_nvenc -pixel_format yuv444p -y /tmp/output.mp4
First, we specify the "mjpeg" instead of the "yuyv422" stream provided by the camera, as yuyv422 is rawvideo and still to heavy on resources here. My video size, then video device. Next I specify my alsa device for sound recording, rather than the cheap on-camera microphone. The key to using Nvidia's nvenc on linux or using FFMpeg, the placement of "-pix_fmt yuv420p" for converting the yuyv422/yuyvj422 input stream to a compatible Nvidia nvenc format, after the input streams and before specifying the output codecs! Then the output alsa and h264 codecs, along with the output filename. (FFMPeg's NvEnc page seems to specify incompatbile or out-dated flags/options.)
TIP: The uncompressed raw video is provided by a yuyv422 stream device from the camera, specified by v4l-ctl. (eg. $ v4l2-ctl --list-formats --device /dev/video2) When pulling the yuyv422 raw video, can push only rawvideo into a *.yuv container. Specifying *.avi container tends to transcode audio/video. This interface is likely used for photos or snapshots by Logitech's Camera Capture.
TIP: Instead of specifying non-indexed randomized /dev/video? numbers as Linux kernel drivers currently provide no indexing unlike additional sound cards, can access the specific camera by using, "/dev/v4l/by-id/usb-046d_HD_Pro_Webcam_C920_89A6F41F-video-index2" a symlink to /dev/video2 device.
TIP: Windows FFMpeg options using DirectShow, within shell or Cygwin:
List Devices
$ ffmpeg -list_devices true -f dshow -i dummy
List a Device's Resolutions
$ ffmpeg -f dshow -list_options true -i video="HD Pro Webcam C920"
Sample Recording
$ ffmpeg -f dshow -i video="HD Pro Webcam C920":audio="Microphone (ASUS Xonar Essence STX Audio Device)" out.mp4
TODO: Can record microphone and video camera activates, but FFMpeg created file doesn't seem to contain a video, only audio?
NOTE: Oddly, the gspca_vc032x module will recognize the Logitech 920s (046d:0892) device string, so if experiencing collisions or problems, try blacklisting or removing the gspca_vc032x driver.
TODO: My Logitech's software Camera Capture created video containers/files contain four additional audio streams rather than just two audio streams for stereo or one audio stream for mono. (FFprobe reports one VideoHandler stream with four SoundHandler containing three AAC streams.) Possibly just capturing all available microphone stream devices? Three are identical kbps with one lacking a few kbps, and upon further analyzing, three contain direct feed from my secondary sound card microphone by testing by directly tapping on the microphone. I could be wrong, and the webcam mics could be extremely sensitive sounding as if I'm tapping on it instead of my secondary mic. This is something that hopefully can be fixed, else it should be considered a bug.
| Standing screen display size | 2.7 Inches |
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