How to take a photo with a webcam? #111
Assignees
Benjamin_Loison (Benjamin Loison)
Clear assignees
Benjamin_Loison (Benjamin Loison)
No Assignees
Notifications
Due Date
No due date set.
Dependencies
No dependencies set.
Reference: Benjamin_Loison/linux#111
Reference in new issue
Block a user
DuckDuckGo search Linux take a photo with a camera.
Would help #9.
Related to Benjamin_Loison/avnc/issues/8.
Output:
on Debian 13 GNOME HP laptop.
Output:
https://www.firestorm.cx/fswebcam/ is not found and https://www.firestorm.cx does not return relevant content.
Note:
DuckDuckGo and Google search Linux ffmpeg get camera photo.
The Ask Ubuntu answer 102774:
Output:
Output:
While it works fine, it seems less clean than with
-vframes 1.Output:
Related to Benjamin_Loison/avnc/issues/8.
For SSH:
Output:
Output:
Output:
DuckDuckGo search ffmpeg to stdout.
The Super User answer 520952:
Output:
Output:
DuckDuckGo and Google search ffmpeg jpg stdout.
https://manpages.debian.org/trixie/ffmpeg/ffmpeg.1.en.html
Checking
-fand format occurrences:Output:
Output:
Output:
Output:
Output:
On Debian 13, how to make the following correctly output and detect a JPEG?
GLM 5.3 Think and Search:
The problem isn't detection — it's that your command never produces any output. Two issues:
file -is a shell pipe, not an ffmpeg argument. ffmpeg has no output file, so it printsAt least one output file must be specifiedand writes nothing to stdout →file -sees an empty stream.-vframes 1is an output option, so placing it before any output triggers theTrailing option(s) found in the command: may be ignoredwarning.Correct command
Expected output:
What each part does
-f v4l2 -i /dev/video0— explicitly declare the input format (optional but avoids auto-detection quirks).-frames:v 1— output option: encode exactly one frame (put it after the input, as an output option).-c:v mjpeg— encode to Motion JPEG (a single MJPEG frame is a standard JPEG file).-f image2 pipe:1— force theimage2muxer and write to stdout. You need-f image2explicitly because ffmpeg won't guess a muxer for a raw pipe.| file -—filereads the piped bytes from stdin.Notes
-hide_bannerjust suppresses the version noise.)ioctl(VIDIOC_QBUF): Bad file descriptor/ buffers warning at the end is harmless cleanup noise from the v4l2 capture device exiting after one frame — it doesn't affect the output.Related to Benjamin_Loison/Improve_websites_thanks_to_open_source/issues/4333.
Output:
Output:
Output:
Manual does not help figure out why
2inimage2.Related to Benjamin-Loison/Signal-Desktop/issues/135.
DuckDuckGo search Linux get camera maximum resolution.
The Ask Ubuntu answer 687140:
Output:
Output:
does not help.
Mistral:
conv_01a1a6e7838c75a8a3f20c15e1ece7b7Prompt:
On Debian 13 how to use maximum resolution (1920x1080) for:
?
GLM 5.3 Think and Search:
The problem
Two separate issues in your output:
image2warning: writing to a pipe requires-update 1(with a single frame) since ffmpeg 5+.Step 1: Check what your camera actually supports
or:
You will almost certainly see that 1920x1080 is only offered as MJPEG, not YUYV. Uncompressed YUYV at 1080p30 is ~1 Gbit/s, which exceeds USB 2.0 bandwidth — that's why cameras cap raw formats at ~640x480/720p and reserve 1080p for MJPEG.
Step 2: Capture at 1920x1080
Key points:
-input_format mjpeg— request the MJPEG stream from the device (this is an input option, so it goes before-i).-video_size 1920x1080— also an input option, before-i.-update 1— fixes thedoes not contain an image sequence patternwarning when writing to a pipe.If MJPEG 1080p exists, the output should now report
1920x1080.If the camera only offers 1080p in YUYV (or you want raw)
Uncompressed 1080p only fits over USB 2.0 at a low frame rate, so drop the framerate:
If the camera doesn't support 1080p at all
Then no ffmpeg option can create real detail — you can only upscale (interpolate) the best native mode:
…but that produces a 1920x1080 file with no more actual detail than the native resolution. In that case use the largest native size listed by
--list-formats-extinstead.Note on
-vframes 1-vframesis deprecated in ffmpeg 7.x; prefer-frames:v 1(both still work, but the latter is the modern syntax).Argument order solves the issue:
Output: