URSA Cam frame rate weirdness

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RandyOK

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URSA Cam frame rate weirdness

PostWed Aug 04, 2021 8:17 pm

our cameraman was shooting along just fine at UHD 59.94. But after a battery change all of the clips recorded at around 40 frames per second which play back fast .
First of all: What caused this?
Second: How can I fix it?
Third: How can I prevent this from happening again?

We checked back the Angelbird card in the camera and it played back fast on the original camera too.
Everything before the battery change is OK and everything shot after the battery change is fast/bad.

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James Alexander Barnett

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Re: URSA Cam frame rate weirdness

PostWed Aug 04, 2021 9:45 pm

Sounds like he might of hit the "off speed" recording button somehow, capturing at 40fps and conformed to playback at 59.94fps.

If you press the fps on the screen it will bring up the frame rate and "off speed" record option.
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RandyOK

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Re: URSA Cam frame rate weirdness

PostWed Aug 04, 2021 10:03 pm

I just checked that. The off speed frame rate was indeed set at 40 frames per second however, the Off speed record select button was in the off position. I am wondering if the hot swap on the battery may have caused it to go into the off speed record mode even though the switch was off. What do you think?
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Jack Fairley

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Re: URSA Cam frame rate weirdness

PostWed Aug 04, 2021 11:48 pm

I think it's more likely that someone accidentally pressed the HFR button.
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Re: URSA Cam frame rate weirdness

PostThu Aug 05, 2021 8:57 am

Which is actually too easy on these cameras. I tend to set HFR to the standard frame rate when not in use as a safety measure (which still doesn't avoid audio sync trouble).
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RandyOK

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Re: URSA Cam frame rate weirdness

PostThu Aug 05, 2021 11:49 am

I would think that but all he did was change a battery that had died between shots.
.
He didn’t have to get into the menus at all.
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John Brawley

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Re: URSA Cam frame rate weirdness

PostThu Aug 05, 2021 3:47 pm

RandyOK wrote:I would think that but all he did was change a battery that had died between shots.
.
He didn’t have to get into the menus at all.


For sure they accidentally hit the HFR button.

It’s easy to do. I usually map it to another function all together. Before you could do that in software I would make it to a very high number so I would notice (hopefully) the exposure change. It happened to me a few times.

You can also use the “lock” function which sill stop accidental toggles.

There’s no way it was only the battery change. Can’t see that happening ever. Unless he held the camera to change the battery holding in the HFR button ;-)

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RandyOK

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Re: URSA Cam frame rate weirdness

PostFri Aug 06, 2021 4:06 am

You must be right!
I was referring to the OFF Frame rate button in the record MENU.
I didn’t realize the HFR button was in that position on the outside of the camera.
Never used it ( on purpose, lol)
Thanks.
I will let my crew know to look out for and avoid this button.

Thanks guys!
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Mike Potton

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Re: URSA Cam frame rate weirdness

PostFri Aug 06, 2021 4:34 am

John Brawley wrote:
There’s no way it was only the battery change.



Totally, very very unlikely but possible, there is a frame rate gremlin in the URSA Mini's, though I haven't seen power downs mess with off speed.

A classic example is if I set my G1 to 50fps braw 4.6k and then change to Prores 422 UHD the camera will change the frame rate to 30fps during the braw->prores reboot. It's a slippery bug and very much an edge case, but it's there. It's possible that a battery swap could trigger it.
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John Brawley

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Re: URSA Cam frame rate weirdness

PostFri Aug 06, 2021 8:52 pm

Mike Potton wrote:
John Brawley wrote:
There’s no way it was only the battery change.



A classic example is if I set my G1 to 50fps braw 4.6k and then change to Prores 422 UHD the camera will change the frame rate to 30fps during the braw->prores reboot. It's a slippery bug and very much an edge case, but it's there. It's possible that a battery swap could trigger it.


No. You just described a codec change which does *require* a reboot and is different code. (and I wonder if it's because there's limitation with other setting when you do that?)

The OP just described the simple act of changing a battery. It's the same firmware.

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Tim Schumann

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Re: URSA Cam frame rate weirdness

PostMon Aug 09, 2021 1:57 am

Mike Potton wrote:A classic example is if I set my G1 to 50fps braw 4.6k and then change to Prores 422 UHD the camera will change the frame rate to 30fps during the braw->prores reboot. It's a slippery bug and very much an edge case, but it's there. It's possible that a battery swap could trigger it.

This is not a bug it is expected behaviour on the URSA Mini Pro 4.6K G1...

The camera will try to keep the frame rate the same but if you choose a format or codec where it can't achieve that frame rate it will switch to the next nearest rate it can.

If you are at 4.6K in Blackmagic RAW 50p and you change to 4.6K ProRes 4:2:2 the highest sensor frame rate in ProRes in that resolution is 40fps so it will adjust down to 30p. If you were in off-speed 40fps in 4.6K Blackmagic RAW and changed to 4.6K ProRes 4:2:2 then it would remain the same between the two after booting into that codec.

If you want to maintain your 50fps rate and shoot in ProRes then you can achieve this by selecting 4.6K 2.4:1, 4K 16:9 or lower resolutions. Once you are at 2160p or lower resolutions in ProRes all project frame rates up to 60fps are supported.

These can of-course be scaled from the full sensor when in ProRes if you don't want to change your angle of view, and you want to use the full 4.6K area of the image sensor.
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Mike Potton

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Re: URSA Cam frame rate weirdness

PostMon Aug 09, 2021 4:56 am

Tim Schumann wrote:This is not a bug it is expected behaviour on the URSA Mini Pro 4.6K G1...


I totally get that it will shift down FPS to align with specs.

However, as per my post I'm talking about UHD, 3840x2160 which the Mini Pro G1 can handle just fine at 50fps prores 422. Yet it still switches to 30fps.
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Tim Schumann

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Re: URSA Cam frame rate weirdness

PostMon Aug 09, 2021 5:34 am

Okay gotcha. Have just tried it here and I see what you are saying.

So if you are in 4.6K Blackmagic RAW and press Ultra HD first and then hit ProRes (assuming that ProRes 422 was the last ProRes codec option you used) before hitting 'Menu' to boot into that codec it will keep the 50fps project rate without changing it.

But if you are in 4.6K Blackmagic RAW and press ProRes first... and then hit Ultra HD and 'Menu' then it will change it to 30fps as it has partially booted into 4.6K ProRes before you have selected the lower resolution.
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Mike Potton

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Re: URSA Cam frame rate weirdness

PostMon Aug 09, 2021 5:57 am

Tim Schumann wrote:Okay gotcha. Have just tried it here and I see what you are saying.

So if you are in 4.6K Blackmagic RAW and press Ultra HD first and then hit ProRes (assuming that ProRes 422 was the last ProRes codec option you used) before hitting 'Menu' to boot into that codec it will keep the 50fps project rate without changing it.

But if you are in 4.6K Blackmagic RAW and press ProRes first... and then hit Ultra HD and 'Menu' then it will change it to 30fps as it has partially booted into 4.6K ProRes before you have selected the lower resolution.


Camera is at my office so can't verify, cheers for the explanation, it's the order that counts.

So if a user wants to switch to UHD Prores 50, they will get different results after the reboot depending on if they select the codec or the resolution first. I guess I tend to change codec first as it's up the top, so it's less of a bug, more of a quirk.

A worthy quirk mind you. It really is a fantastic menu system, to have resolution and codec laid out on the one page compared with the usual deep-dive sub menus...
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John Brawley

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Re: URSA Cam frame rate weirdness

PostMon Aug 09, 2021 7:13 am

Mike Potton wrote:
A worthy quirk mind you. It really is a fantastic menu system, to have resolution and codec laid out on the one page compared with the usual deep-dive sub menus...


And I think I might add, they don't really crash or go buggy. Hardware fails are more likely than software glitches. The OS is really remarkably rock solid, especially compared to the big boys. I've seen software crashes on both Alexa and RED. Not so much on BMD cameras.

At worst it's more with third parties like lens adaptors and lens comms, which seems to more to do with it being at the mercy of third party vendors.

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