PiCamera() does not work with hdmi off

[ajaborsk]

I'm using RPi without screen and on batteries, so I'd like to switch off hdmi to save some mW (tvservice -o). But if I do, PiCamera() does not initialize (complains about invalid camera preview format in preview port settings). raspistill works well in the same condition, but I can't tell if a preview is showed or not.

[waveform80]

Yup, confirmed - unfortunately this is not a combination I've ever tested before and there's no easy workaround at the moment other than enabling HDMI. I'll look into this and try to get it fixed for 1.6

[waveform80]

Okay - I know what the issue is here : picamera attempts to be friendly and sets its initial resolution to the display resolution which is determined with bcm_host.graphics_get_display_size. When HDMI is disabled this returns -1 (which we don't check), and leaves the resolution as 0x0 (which naturally fails when we try to configure the preview). I'll add a check for a -1 return code and default the res to something sensible like 720p in that circumstance.