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linux - Can v4l2 be used to read audio and video from the ...
https://stackoverflow.com/questions/917060/can-v4l2-be-used-to-read-audio-and-video-from-the-same-device
IF you want your driver to play with gstreamer etc. a separate audio device generally is what is expected. Most of the cheap v4l2 capture card's audio is only an analog pass through with a volume control requiring a jumper to capture the audio via the sound card's line input. Share. Improve this answer.
Documentation:Modules/v4l2 - VideoLAN Wiki
https://wiki.videolan.org/Documentation:Modules/v4l2/
These options do not apply to audio streams in compressed data. v4l2-adev < string > : Audio input device default value: "". v4l2-audio-method < integer > : Allowed audio input methods (bitmask: 1 for OSS, 2 for ALSA) default value: 3. v4l2-stereo : Capture audio in stereo default value: enabled. v4l2-samplerate < integer > : Audio input sample ...
Part I - Video for Linux API — The Linux Kernel …
https://www.kernel.org/doc/html/v4.9/media/uapi/v4l/v4l2.html
Removed VIDIOC_*_OLD from videodev2.h header and update it to reflect latest changes. Added the multi-planar API. Removed obsolete vtx (videotext) API. Added documentation for the Digital Video timings API. Now, revisions will match the kernel version where the V4L2 API changes will be used by the Linux Kernel.
1.12. V4L2 Controls — The Linux Kernel documentation
https://www.kernel.org/doc/html/v4.10/media/kapi/v4l2-controls.html
static int foo_s_ctrl(struct v4l2_ctrl *ctrl) { struct foo *state = container_of(ctrl->handler, struct foo, ctrl_handler); switch (ctrl->id) { case V4L2_CID_AUDIO_VOLUME: { struct v4l2_ctrl *mute = ctrl->cluster[AUDIO_CL_MUTE]; write_reg(0x123, mute->val ? 0 : ctrl->val); break; } case V4L2_CID_CONTRAST: write_reg(0x456, ctrl->val); break; } return 0; }
8.67. V4L2 read() — The Linux Kernel documentation
https://www.kernel.org/doc/html/v4.11/media/uapi/v4l/func-read.html
8.67.4. Description¶. read() attempts to read up to count bytes from file descriptor fd into the buffer starting at buf.The layout of the data in the buffer is discussed in the respective device interface section, see ##. If count is zero, read() returns zero and has no other results. If count is greater than SSIZE_MAX, the result is unspecified.Regardless of the count value each read() …
Part I - Video for Linux API — The Linux Kernel …
https://www.kernel.org/doc/html/latest/userspace-api/media/v4l/v4l2.html
Part I - Video for Linux API. This part describes the Video for Linux API version 2 (V4L2 API) specification. Revision 4.5. Table of Contents. 1. Common API Elements. 1.1. Opening and Closing Devices. 1.1.1.
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