6by9
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
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Re: Hardware camera sync pulses

Thu Aug 02, 2018 10:02 am

gordon77 wrote:
Thu Aug 02, 2018 8:08 am
6by9 wrote:
Mon Aug 07, 2017 4:00 pm
There have been various requests over the years for external triggers for frame synchronisation. Generally it's been stated that doing such things isn't trivial, and it wasn't. However, as of the 22nd July firmware, there is support for repurposing the camera LED GPIO to change state on frame start and frame end interrupts.....
I don't quite see how this externally triggers cameras, it appears it just shows you when a picture is being taken. Anyone got any details how it can be used to trigger cameras?
It can't be, and I don't think I've ever said it could be.
You can use it alongside the frame rate control to produce effectively a phase lock loop that will pull things in to sync over a few seconds and keep them there.
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gordon77
Posts: 3339
Joined: Sun Aug 05, 2012 3:12 pm

Re: Hardware camera sync pulses

Thu Aug 02, 2018 12:24 pm

6by9 wrote:
Thu Aug 02, 2018 10:02 am
gordon77 wrote:
Thu Aug 02, 2018 8:08 am
6by9 wrote:
Mon Aug 07, 2017 4:00 pm
There have been various requests over the years for external triggers for frame synchronisation. Generally it's been stated that doing such things isn't trivial, and it wasn't. However, as of the 22nd July firmware, there is support for repurposing the camera LED GPIO to change state on frame start and frame end interrupts.....
I don't quite see how this externally triggers cameras, it appears it just shows you when a picture is being taken. Anyone got any details how it can be used to trigger cameras?
It can't be, and I don't think I've ever said it could be.
You can use it alongside the frame rate control to produce effectively a phase lock loop that will pull things in to sync over a few seconds and keep them there.
Thanks. It looks like I misunderstood "There have been various requests over the years for external triggers for frame synchronisation."

6by9
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 5549
Joined: Wed Dec 04, 2013 11:27 am
Location: ZZ9 Plural Z Alpha, aka just outside Cambridge.

Re: Hardware camera sync pulses

Sun Aug 05, 2018 1:05 pm

gordon77 wrote:
Thu Aug 02, 2018 12:24 pm
Thanks. It looks like I misunderstood "There have been various requests over the years for external triggers for frame synchronisation."
True, I could have possibly phrased that better - now edited.
This is purely an output which synchronised with frame start/end events as received by the SoC.
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
Please don't send PMs asking for support - use the forum.
I'm not interested in doing contracts for bespoke functionality - please don't ask.

Kozuch
Posts: 62
Joined: Sun Aug 10, 2014 10:35 am

Re: Hardware camera sync pulses

Sat Sep 15, 2018 6:27 pm

Do the camera sync pulses also work with the very high FPS mode that user HermannSW showed in the Raw sensor access / CSI-2 receiver peripheral thread? And also here. He claims some 900-1000 FPS.

6by9
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 5549
Joined: Wed Dec 04, 2013 11:27 am
Location: ZZ9 Plural Z Alpha, aka just outside Cambridge.

Re: Hardware camera sync pulses

Sat Sep 15, 2018 6:53 pm

Kozuch wrote:
Sat Sep 15, 2018 6:27 pm
Do the camera sync pulses also work with the very high FPS mode that user HermannSW showed in the Raw sensor access / CSI-2 receiver peripheral thread? And also here. He claims some 900-1000 FPS.
IIRC then no. They only work with the full camera stack, not rawcam/raspiraw.
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
Please don't send PMs asking for support - use the forum.
I'm not interested in doing contracts for bespoke functionality - please don't ask.

Kozuch
Posts: 62
Joined: Sun Aug 10, 2014 10:35 am

Re: Hardware camera sync pulses

Sat Sep 15, 2018 10:50 pm

That really is a pity. Do you think there could be a way to get the closest possible to the moment when a frame is taken in raw camera mode?

6by9
Raspberry Pi Engineer & Forum Moderator
Raspberry Pi Engineer & Forum Moderator
Posts: 5549
Joined: Wed Dec 04, 2013 11:27 am
Location: ZZ9 Plural Z Alpha, aka just outside Cambridge.

Re: Hardware camera sync pulses

Sun Sep 16, 2018 9:25 am

Kozuch wrote:
Sat Sep 15, 2018 10:50 pm
That really is a pity. Do you think there could be a way to get the closest possible to the moment when a frame is taken in raw camera mode?
I can do the same thing as for the main stack (it's less plumbing there too), although it still makes little real world sense with a rolling shutter camera where there isn't a single instant of capture.
Software Engineer at Raspberry Pi Trading. Views expressed are still personal views.
Please don't send PMs asking for support - use the forum.
I'm not interested in doing contracts for bespoke functionality - please don't ask.

Kozuch
Posts: 62
Joined: Sun Aug 10, 2014 10:35 am

Re: Hardware camera sync pulses

Sun Sep 16, 2018 1:01 pm

Sync does make a big reason for rolling shutter, especially when combined with a special camera mode (raw in this case) which further shortens the image readout etc. (in low resolution, but that is OK for many computer vision applications). There are also moments when the shutter speed is very short and the rolling shutter is negligible (I can think of a sunny outdoor scene etc.).

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