Hello, After some discussions in the WIP thread, I decided to send a patch without the part in question. So here is the "Using a Webcam" chapter which does only mention that it's necessary to set permissions of /dev/video* to the user. I leaves out the details about how to do it best.
If there are new developments, like a video group or a sysctl video.record knob, I'll send delta patches to describe the behavior. OK? Best Regards, Stefan Index: faq/faq13.html =================================================================== RCS file: /cvs/www/faq/faq13.html,v retrieving revision 1.220 diff -u -p -u -p -r1.220 faq13.html --- faq/faq13.html 19 May 2020 02:01:48 -0000 1.220 +++ faq/faq13.html 19 Sep 2020 17:26:38 -0000 @@ -66,6 +66,7 @@ FAQ - Multimedia <li><a href="#default" >Choosing the Default Audio Device</a> <li><a href="#audioprob" >Debugging Audio Problems</a> <li><a href="#midi" >Using MIDI Instruments</a> + <li><a href="#webcam" >Using a Webcam</a> <!-- XXX <li><a href="#playDVD" >Playing DVDs</a> <li><a href="#burnCD" >Burning CDs and DVDs</a> @@ -491,6 +492,196 @@ output: <pre class="cmdbox"> $ <b>midicat -q midi/0 -q midithru/0</b> </pre> + +<h2 id="webcam">Using a Webcam</h2> + +<h3>Supported Hardware</h3> + +<p> +Most webcams today work according to the USB Video Class +(UVC) specification, which is supported by the <a +href="https://man.openbsd.org/uvideo";>uvideo(4)</a> device driver and +attaches to the <a href="https://man.openbsd.org/video.4";>video(4)</a> +device. The manpage lists some supported devices, but there is a +good chance that other devices work as well. For example, webcams in +Lenovo Thinkpads laptops do usually work. + +<p> +A supported webcam (or other video device) shows up in <code>dmesg</code> +like this: + +<pre class="cmdbox"> +uvideo0 at uhub0 port 8 configuration 1 interface 0 "Azurewave Integrated Camera" rev 2.01/69.05 addr 10 +video0 at uvideo0 +uvideo1 at uhub0 port 8 configuration 1 interface 2 "Azurewave Integrated Camera" rev 2.01/69.05 addr 10 +video1 at uvideo1 +</pre> + +<p> +You see that an <code>uvideo</code> device was detected and has +been attached to <code>video0</code>. This device will be accessible +through <code>/dev/video0</code>. + +<p> +Modern laptops sometimes attach a second video device, which is the +infrared camera for face recognition. The second camera does not produce +a usable video stream. + +<p> +You can find the usable camera with the <a +href="https://man.openbsd.org/video";>video(1)</a> command: + +<pre class="cmdbox"> +$ <b>video -q -f /dev/video0</b> +video device /dev/video0: + encodings: yuy2 + frame sizes (width x height, in pixels) and rates (in frames per second): + 320x180: 30 + 320x240: 30 + 352x288: 30 + 424x240: 30 + 640x360: 30 + 640x480: 30 + 848x480: 20 + 960x540: 15 + 1280x720: 10 + controls: brightness, contrast, saturation, hue, gamma, sharpness, white_balance_temperature + +$ <b>video -q -f /dev/video1</b> +video: /dev/video1 has no usable YUV encodings +</pre> + +<p> +The usable camera device shows supported resolutions and framerates. +Note that the framerates only apply to the uncompressed YUY2 stream. More +on that in <a href="#recvideo">Recording a webcam stream</a>. + +<h3>Using a webcam as user</h3> + +<p> +To use the webcam as regular user, you need to change the device +permissions. Only root is allowed to access video devices by default. + +<pre class="cmdbox"> +$ <b>doas chown $USER /dev/video0</b> +</pre> + +<h3 id="recvideo">Recording a webcam stream</h3> + +<p> +This section uses <code>ffplay</code> and <code>ffmpeg</code> from +graphics/ffmpeg. To find out what your camera is capable of, run the +following command: + +<pre class="cmdbox"> +$ <b>ffplay -f v4l2 -list_formats all -i /dev/video0</b> +[...] +[video4linux2,v4l2 @ 0x921f8420800] Compressed: mjpeg : MJPEG : 1280x720 320x180 320x240 352x288 424x240 640x360 640x480 848x480 960x540 +[video4linux2,v4l2 @ 0x921f8420800] Raw : yuyv422 : YUYV : 640x480 320x180 320x240 352x288 424x240 640x360 848x480 960x540 1280x720 +</pre> + +<p> +At the end of the output, you'll find two lines similiar to the two +above. + +<p> +The first line shows resolutions supported in the uncompressed YUYV +format. The frame rates in this format can be very low. + +<p> +The second line shows the supported MJPEG compressed video resolutions, +which deliver much higher framerates (usually 30fps or 60fps). + +<p> +Now try to play the webcam stream. Choose one of the MJPEG resolutions +and run: + +<pre class="cmdbox"> +$ <b>ffplay -f v4l2 -input_format mjpeg -video_size 1280x720 -i /dev/video0</b> +[...] +Input #0, video4linux2,v4l2, from '/dev/video0':B sq= 0B f=0/0 + Duration: N/A, start: 1599377893.546533, bitrate: N/A + Stream #0:0: Video: mjpeg (Baseline), yuvj422p(pc, bt470bg/unknown/unknown), 1280x720, 30 fps, 30 tbr, 1000k tbn, 1000k tbc +</pre> + +The webcam stream should be displayed. Ffplay also shows the used +resolution and the framerate (fps) used. + +<p> +If this works, you can go ahead and record the video with ffmpeg: + +<pre class="cmdbox"> +$ <b>ffmpeg -f v4l2 -input_format mjpeg -video_size 1280x720 -i /dev/video0 ~/video.mkv</b> +</pre> + +End the recording with "q". You have now recorded your stream to file +<code>~/video.mkv</code>. + +<h3>Controlling webcam settings</h3> + +<p> +Webcams usually have brightness, contrast and other controls. +<a href="https://man.openbsd.org/video.1";>Video(1)</a> +allows you to alter these settings. + +<p> +First find out which supported controls your camera has: + +<pre class="cmdbox"> +$ <b>video -c</b> +brightness=128 +contrast=32 +saturation=64 +hue=0 +gamma=120 +sharpness=3 +white_balance_temperature=auto +</pre> + +<p> +You can change for example the brightness setting to 200: + +<pre class="cmdbox"> +$ <b>video brightness=200</b> +brightness: 128 -> 200 +</pre> + +<p> +If you would like to reset all settings to their defaults, you can do so with: + +<pre class="cmdbox"> +$ <b>video -d</b> +$ <b>video -c</b> +brightness=128 +contrast=32 +saturation=64 +hue=0 +gamma=120 +sharpness=3 +white_balance_temperature=auto +</pre> + +<p> +Some settings, like the <code>white_balance_temperature</code> support +automatic adjustments. You can set them to a fixed value or set them to +"auto", which lets the camera decide and use whatever value it thinks is +best. + +<h3>Access webcam in chromium</h3> + +<p> +Chromium has access to <code>/dev/video</code> by default. To +allow Chromium to access other video devices, you need to add +the device paths to <code>/etc/chromium/unveil.main</code> and +<code>/etc/chromium/unveil.utility_video</code> + +<h3>Access webcam in firefox</h3> + +<p> +Firefox has access to <code>/dev/video</code> and <code>/dev/video0</code> +by default. To allow Firefox to access other video devices, you need to +add the device paths to <code>/etc/firefox/unveil.main</code>. + <!-- XXX To record MIDI files, you can use the <code>smfrec</code> utility bundled in
