Dropped Frames on URSA Mini Pro G1

I recently had to shoot a pretty high level tv commercial as B Cam Op. I used my privately owned Ursa mini Pro G1, there was also a steadicam Op with a G2. We both shot 4.6K BMRaw at 50fps rendered to a 25fps project. We used the same approved Cfast 2.0 cards. This was shot with no compression so Q0 if I recall correctly.

Long story short. We had one opportunity to capture a live moment of a father and son meeting for the first time in years and couldn't have anything go wrong, since you can't go for a second take...

So, after the shoot, we found that my camera had dropped frames at certain points. The CFast 2.0 card has never let me down before and is an approved card (I won't mention the brand).

So my question is - This Ursa was advertised to me that it can do 50fps at 4.6K RAW at the time. BMRaw is even more compressed, so I did not expect this at all. What I want to know is, firstly, who is at fault here? (Since I've lost a large client)

Secondly, why are we not offered an upgrade to the G2 if this is a known issue? The G2 came out a week after I bought the damn thing!

I feel Blackmagic really let me down badly. I've been with their cameras since the beginning and went through all the **** with purple flares etc. Once again bitterly dissapointed in the camera in the end.

I hope I get some response from BM.

[Tim Schumann]

If you look at the URSA Mini Manual it clearly describes how Q0 works...

To solve this problem, Blackmagic RAW also has an alternative codec choice called constant quality. This codec is technically called a variable bitrate codec, but what it’s really doing is allowing the size of the file to grow if your images need extra data. There is no upper limit on the file size if you need to encode an image but maintain quality.

So Blackmagic RAW set to the constant quality setting will just let the file grow as big as it needs to be to encode your images. It also means the files could be larger or smaller depending on what you are shooting.

from Page 33 of the 6.4 URSA Mini Manual

Q0 and Q5 refer to different levels of quantization. Q5 has a greater level of quantization but offers a greatly improved data rate. As mentioned above, the constant quality setting can result in files that grow and shrink quite a lot, depending on what you are shooting. This also means it’s possible to shoot something and see the file size increase to beyond what your media card can keep up with. It could result in dropped frames.

from Page 34 of the 6.4 URSA Mini Manual

My heart goes out to you and I am truly sorry you missed this shot but we have pretty clearly stated how this format works. 4.6K at Q0 is not something we would recommend for this type of shooting because it prioritises image quality over predictable file sizes. It is perfect for feature films, commercials or special effects work at 4.6K up to 30p but if you are after predictable file sizes at 4.6K with higher frame rates and you can't afford to go for a second take then constant bitrate settings like 3:1, 5:1, 8:1 and 12:1 are what you should be choosing.

If you did not notice dropped frames during your shoot it might be worth turning the 'stop record if card drops frames' feature to 'on'. It is on page 3 of our record menu. It will halt your recording instantly if any dropped frames are detected. It is switched on by default so you may have switched it off at some stage.

Thanks for the response. I didn't realise this could happen.

Will the G2 have the same problem?

Just for the record I used constant quality at Q0.

When you want to shoot 4.6k BRAW Q0 at 50 fps you need a sustained write speed of 460 GByte/s.

With one of these https://cinediskpro.com/cfast-to-ssd and a Samsung 860 pro https://www.anandtech.com/show/12348/the-samsung-860-pro-512gb-and-4tb-ssd-review/6
you can.

Overprovision the drive with atleast 10% for background garbage collection.
(format it to 90% usable space or less, so you have atleast an overprovisioning of 10%).

It's a lot cheaper then CFast.

If you can manage it, since all SSDs I’ve seen available are multi-cell (usually 2 ‘layers’), you’ll get the fastest Write times if you do not exceed half the capacity of the SSD. That might help. Still those bitrates may be too high. It might take some testing in a complex scene with lots happening to verify it works.

I’ve shot 4K in Q0 successfully. So that might be an option rather than use 4.6K.


Sent from my iPhone using Tapatalk

Chris, when shooting once in a live time footage, I would always recommend to have a secondary recording as a backup. What I do in such a case is having a Shogun Inferno connected to the main SDI out and recording an UHD ProRes backup. While this is not the same as BRAW, at least you got a high quality recording for any case when things go wrong with your main recording.

[Tim Schumann]

Will the G2 have the same problem?

This is not a camera problem. Yes you would get the same result on a G2 in Blackmagic RAW Q0 as it works in exactly the same way. You need to choose the right format for what you are shooting...

When you want to shoot 4.6k BRAW Q0 at 50 fps you need a sustained write speed of 460 GByte/s.

As it is variable and is the lowest possible quantisation Q0 can actually go even higher than 460GB/s at 4.6K 50fps if it is a very difficult to compress scene with high contrast and lots of sharp fine detail. As mentioned above if you absolutely can't afford to drop frames then using Constant Bitrate 3:1, 5:1, 8:1 or 12:1 will mean that your recordings have a predictable maximum data rate.

When you want to shoot 4.6k BRAW Q0 at 50 fps you need a sustained write speed of 460 GByte/s.

As it is variable and is the lowest possible quantisation Q0 can actually go even higher than 460GB/s at 4.6K 50fps if it is a very difficult to compress scene with high contrast and lots of sharp fine detail. As mentioned above if you absolutely can't afford to drop frames then using Constant Bitrate 3:1, 5:1, 8:1 or 12:1 will mean that your recordings have a predictable maximum data rate.

From the BMD website

https://images.blackmagicdesign.com/images/products/blackmagicraw/landing/encoding/graph-en-xl@2x.png?_v=1536892540

Full 4.6k sensor 4608 x 2592 @ 30 fps

Q0 between 274(highest) and 110(lowest) MByte/s

(274MB/s / 30fps) x 50fps = 457 MByte/s ~ 460 MByte/s (compression rate of 2:1).

[Tim Schumann]

Yes this is based on normal shooting conditions but if someone fires a glitter cannon or drops a stack of confetti then at Q0, as there is absolutely the lowest amount of quantisation possible, it will back off on the compression accordingly and may go to a ratio lower than the 2:1 that is listed there.

Have a look in the URSA Mini manual on page 33.

Yes this is based on normal shooting conditions but if someone fires a glitter cannon or drops a stack of confetti then at Q0, as there is absolutely the lowest amount of quantisation possible, it will back off on the compression accordingly and may go to a ratio lower than 2:1.

Is this an official statement?

Because when it is, it will have serious consequences (lawyers and money kind of consequences).

So far we had no trouble shooting 4.6k BRAW 50 fps Q0 on our UMP G1's combined with Samsung 850 or 860 pro's(2TByte versions with 10% overprovisioning).

[Tim Schumann]

The official statements are in the manual... I am trying to help the person who started the thread understand why they might have dropped frames.

The official statements are in the manual... I am trying to help the person who started the thread understand why they might have dropped frames.

The help you and the rest of the BMD-team provide is highly valued.

BMD and it's products are more than good enough, to be succesful without unclear statements

4608 x 2592
Blackmagic RAW Q0 - 110 to 274 MB/s *
Blackmagic RAW Q5 - 27 to 78 MB/s **

* Constant Quality setting Q0 storage rates quoted are indicative only, based on a 2:1 - 5:1 compression range.
** Constant Quality setting Q5 storage rates quoted are indicative only, based on a 7:1 - 20:1 compression range.
Actual storage rates are entirely dependent on image subject matter.

I have never heard an ALEXA 65 user complaining about the data rate(they want the best possible picture), I have heard RED 8k users complaning about the compression rate of 5:1 at 24fps (they sometimes want a lower compression rate, compression kills the picture).

(Visually)Lossless compressed upto uncompressed data rates for the highest possible picture quality is also a good statement, the ones who care more about compression or fixed data rates can use the fixed compression ratios.

I think it would be useful, if Chris Ras could describe the content of the scene where he encountered the dropped frames so it would be easier to know what was going on.

Yes this is based on normal shooting conditions but if someone fires a glitter cannon or drops a stack of confetti then at Q0, as there is absolutely the lowest amount of quantisation possible, it will back off on the compression accordingly and may go to a ratio lower than 2:1.

Is this an official statement?

Because when it is, it will have serious consequences (lawyers and money kind of consequences).

So far we had no trouble shooting 4.6k BRAW 50 fps Q0 on our UMP G1's combined with Samsung 850 or 860 pro's(2TByte versions with 10% overprovisioning).

Misha, I am quoting the manual:

Blackmagic RAW also has an alternative codec choice called constant
quality. This codec is technically called a variable bitrate codec, but what it’s really doing is
allowing the size of the file to grow if your images need extra data. There is no upper limit on
the file size if you need to encode an image but maintain quality.

So Blackmagic RAW set to the constant quality setting will just let the file grow as big as it
needs to be to encode your images. It also means the files could be larger or smaller
depending on what you are shooting.

And:

Q0 and Q5 refer to different levels of quantization. Q5 has a greater level of quantization but
offers a greatly improved data rate. As mentioned above, the constant quality setting can result
in files that grow and shrink quite a lot, depending on what you are shooting. This also means
it’s possible to shoot something and see the file size increase to beyond what your media card
can keep up with. It could result in dropped frames. However the benefit is that you can
instantly see if this happens on a shoot and then investigate your settings vs quality.

Misha, I am quoting the manual:

Blackmagic RAW also has an alternative codec choice called constant
quality. This codec is technically called a variable bitrate codec, but what it’s really doing is
allowing the size of the file to grow if your images need extra data. There is no upper limit on
the file size if you need to encode an image but maintain quality.

So Blackmagic RAW set to the constant quality setting will just let the file grow as big as it
needs to be to encode your images. It also means the files could be larger or smaller
depending on what you are shooting.

And:

Q0 and Q5 refer to different levels of quantization. Q5 has a greater level of quantization but
offers a greatly improved data rate. As mentioned above, the constant quality setting can result
in files that grow and shrink quite a lot, depending on what you are shooting. This also means
it’s possible to shoot something and see the file size increase to beyond what your media card
can keep up with. It could result in dropped frames. However the benefit is that you can
instantly see if this happens on a shoot and then investigate your settings vs quality.

IMO those quotes should have been on the page where the Q0, 2:1..5:1 are now.
Q0, 2:1..5:1 is implying a data rate or gives the impression between which values the data rate will be.

I would rather see BMD being proud that they have a codec that values capture quality above all(high bitrate when needed, compressed when possible), even if it becomes near the size of uncompressed RAW under certain circumstances (confetti bomb type of high frequency footage).

And yep, I was overreacting and apologize for this.

This is all good stuff. I recently lost a live event recording at ProResHQ 4.6k going to a Samsung T5 because of a usb-c cable that did not have 20gbps through-put. Dropped frames during recording (have done that before but still salvagable footage)...but this time the recording just freezes the video (and appears as "media offline" screen in resolve) for large sections of the event. Bummer to find this out afterwards, but lesson learned: If you get a frame dropped error...quickly lower your quality level or don't get anything....

I'd never shoot anything important without having the camera set to stop at dropped frames.
That said, if the damage has already happened, it can be fixed to some degree if you only have occasional drops. The BRAW player will then play it and freeze the last frame before the missing one(s). If that shows only as a short 'hiccup', I can explain you the process.