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7.1. Differences between V4L and V4L2 — The Linux …
https://www.kernel.org/doc/html/v4.9/media/uapi/v4l/diff-v4l.html
The VIDIOCGAUDIO and VIDIOCSAUDIO ioctl and struct video_audio are used to enumerate the audio inputs of a V4L device. The equivalent V4L2 ioctls are VIDIOC_G_AUDIO and VIDIOC_S_AUDIO using struct v4l2_audio as discussed in Audio Inputs and Outputs. The audio “channel number” field counting audio inputs was renamed to index.
Can v4l2 be used to read audio and video from the same …
https://stackoverflow.com/questions/917060/can-v4l2-be-used-to-read-audio-and-video-from-the-same-device
Even on the client side, everything seems to assume v4l is just video, like ffmpeg's libavdevice. Do I need to have my driver create two separate devices, a v4l2 device and an alsa device? It seems like this makes the job of keeping audio and video in sync much more difficult.
cannot get audio from usb v4l device - The VideoLAN Forums
https://forum.videolan.org/viewtopic.php?t=30923
[00000290] v4l demuxer error: cannot set audio format (16b little endian) (Inappropriate ioctl for device) vlc is from debian version 0.8.6-svn20061012.debian-2, the camera is a Logitech QuickCam 4000 Pro USB webcam and the kernel is a debian 2.6.18-3
V4L capturing - LinuxTVWiki
https://linuxtv.org/wiki/index.php/V4L_capturing
for VIDEO_DEVICE in /dev/video* ; do echo -e "\n\n$VIDEO_DEVICE\n" ; v4l2-ctl --device=$VIDEO_DEVICE --list-inputs ; done. Usually you will see e.g. a webcam with a single input and a TV card with multiple inputs. If you're still not sure which one you want, try each one in turn: mpv av://v4l2:<device> tv:///<whichever-input-number-you-connected> # or ... mpv --tv …
15. The ivtv driver — The Linux Kernel documentation
https://www.kernel.org/doc/html/v4.12/media/v4l-drivers/ivtv.html
This device only captures audio. This should be replaced by an ALSA device in the future. Note that there is no corresponding raw audio output device, this is not supported in the decoder firmware. /dev/video32. The raw video capture device(s) Read-only. The raw YUV video output from the current video input. The YUV format is non-standard (V4L2_PIX_FMT_HM12).
Video4Linux: What about Output?
https://elinux.org/images/5/59/Elc09_mattporter_v4l.pdf
Output device is normally used to send the resultant video stream to an external analog/digital video interface If you have a “special” device, the stock V4L video standards don’t always make sense The same is true for enumerating outputs, a special device might just have an internal buffer as a “physical output
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