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iizukanao / picam

Audio/video recorder for Raspberry Pi with language agnostic API
GNU Lesser General Public License v2.1
488 stars 78 forks source link

After a few minutes framerate drops very low but CPU is fine #133

Open JamesSwift opened 4 years ago

JamesSwift commented 4 years ago

Firstly, thank you so much for this amazing project! It's been really helpful with my baby monitor and a few other cameras.

When I start picam on my pi zero w's it works amazingly, but after a few minutes, suddenly the perceived framerate drops to almost 2 fps. The cpu is running around half and the memory usage is around half too so there doesn't seem to be a leak. The video will continue indefinitely (tested for round 20 hours so far), but it never gets back to the smooth frame-rate it started with. I'm having no joy in tracking this down. Any ideas?

iizukanao commented 4 years ago

Thanks for using picam. What command line options are you using? You can use -f <fps> option in order to set a fixed frame rate, like -f 30.

JamesSwift commented 4 years ago

Thanks for the quick reply! I'm running:

picam -o /run/shm/hls --autoex --time --rotation 180 -w 1080 -h 810 -v 5000000 --volume 20 --alsadev hw:1,0

I've come up with a working theory. I use the autoex flag, and the cameras are in low light (baby's room). When I increase the light the perceived frame-rate increases. So I think the exposure is being boosted to maybe 1/3 second by autoex during darker periods. What's weird though is that if I restart picam it starts with a short exposure then after a few minutes it goes back to the long exposure.

iizukanao commented 4 years ago

You're right, --autoex automatically enables --vfr (variable frame rate) mode. Don't use --autoex and use --fps <fps> instead if you want a fixed frame rate. When --autoex is used, picam starts with short exposure first.