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gphoto / libgphoto2

The libgphoto2 camera access and control library.
GNU Lesser General Public License v2.1
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vcamera prints error messages about opening invalid filename upon startup #842

Closed RReverser closed 2 years ago

RReverser commented 2 years ago

When using virtual camera, I've noticed that I'm always getting error message like

001,001: No such file or directory

upon startup, even though everything works fine afterwards.

I've tracked it down to this piece of code: https://github.com/gphoto/libgphoto2/blob/8b462f8c835b9d3ab0cee4117e0b0458dac00445/libgphoto2_port/vusb/vcamera.c#L1802-L1816

Basically, vcam_open receives port like usb:001,001 from camera_init, truncates it to second half and then for some reason tries to open what's left (001,001), fails and prints an error via perror.

I could either remove perror code or that code altogether, but I suppose it serves some purpose which is not documented in the file, so I'm not confident with making any fixes there. @msmeissn could you help out?

RReverser commented 2 years ago

Thanks for removing the warning. I wonder though, should it even try to open filenames like 001,001 in the first place? Maybe it could skip that branch altogether for usb: ports?

msmeissn commented 2 years ago

Reason is that the vusb driver doubles as both a virtual ptp camera and a fuzzing driver. over the path statement it is fed the fuzzing data.

RReverser commented 2 years ago

Could fuzzing data be fed under custom prefix only? E.g. when someone passes vusb:some_path, then some_path should be used for fuzzing, but when a regular usb:... prefix is used (which is the default when using gp_camera_autodetect), then assume it's just virtual ptp camera?

msmeissn commented 2 years ago

i just put all the fuzzing code behind an ifdef FUZZING so it does not confuse the virtual ptp usage. ;)

RReverser commented 2 years ago

Thanks!

jim-easterbrook commented 1 year ago

I'm glad I found this bug report. I was having difficulty using a virtual camera with python-gphoto2 until I built it with libgphoto2 compiled from the current GitHub repos. Keenly awaiting the next release of libgphoto2 now. (-: