Weird duplicated frame problem with BM Camera app 1.2

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Chris Nielsen

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Weird duplicated frame problem with BM Camera app 1.2

PostSat Dec 09, 2023 7:05 pm

Hi everyone.

Hopefully this is the right place to post this. Long time Resolve and BM camera fan here. I’ve picked up an iPhone 15 pro max as it was time for a new phone but also I want to use BM Camera app with the intention of using the phone to shoot ProRes in LOG when I am travelling on my motorbike and can’t take a proper camera.

Trying it out with the new phone and I’ve got a bizarre problem. I noticed doing some test shots that the footage seems to ‘stutter’ which is especially noticeable when panning. Looking closer at it in Resolve, if I step through the footage using the arrow keys, every few frames there will be an extra duplicate frame added. It looks like… pan pan pan stationary pan pan pan…. Rinse and repeat.

I’ve tried this using every flavour of ProRes (using Apple LOG only so far) and it seems to just change the frequency of these extra frames. It’s like the opposite of dropped frames. I have tried it shooting just into the app and also to an external ssd. Also I tried in HD and it made no difference. Stock camera app doesn’t exhibit this issue

Any ideas?

Thanks!

Chris
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Uli Plank

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Re: Weird duplicated frame problem with BM Camera app 1.2

PostSun Dec 10, 2023 1:36 am

I have not seen this in my quite thorough tests of the iPhone.
Can you check the variations of the frame rate in MediaInfo?
Did you have any stabiliser activated? Try to switch them off.
What happens if you record log in HEVC?
Maybe AI can help you. Or make you obsolete.

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Chris Nielsen

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Re: Weird duplicated frame problem with BM Camera app 1.2

PostSun Dec 10, 2023 4:44 am

I've not used MediaInfo before so unsure how to interpret it's result. When examining a clip that is set to 29.97, it says Frame Rate 28.997, Min frame rate 28.972 and Max frame rate 29.014.

None of those things you suggested helped, but I noticed something interesting. When set to record 29.97, it adds an additional frame every 30 frames. When set to 24 fps, it adds one every *fifth* frame, as in you get four frames of motion and one stationery frame.
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Uli Plank

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Re: Weird duplicated frame problem with BM Camera app 1.2

PostSun Dec 10, 2023 4:50 am

What is your timeline setting?
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Chris Nielsen

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Re: Weird duplicated frame problem with BM Camera app 1.2

PostSun Dec 10, 2023 4:59 am

Of course that would be a schoolboy error wouldn't it lol

I created a timeline and just dumped everything in and didn't think about timeline settings.

I've just created a new timeline set to 29.97 and put the 29.97 clips in it. Problem persists (also the problem is visible in QT player, not just Resolve)

On a 24 fps timeline with 24fps clips, it doesn't exhibit the problem - I checked every frame in one clip and no duplicates.

I usually shoot 29.97 because 24 looks like jittery garbage on my machine which I assume is the result of a pulldown since the monitor is probably 60hz. 29.97 plays smoothly on it so that's what I use. Is it possible I'm the only one silly enough to use 29.97? lol
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Chris Nielsen

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Re: Weird duplicated frame problem with BM Camera app 1.2

PostSun Dec 10, 2023 7:50 am

Update: Further testing reveals 30p is fine, 24p is fine, it's just 29.97 that's causing me the issue
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Steve Alexander

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Re: Weird duplicated frame problem with BM Camera app 1.2

PostSun Dec 10, 2023 1:58 pm

Chris Nielsen wrote:Update: Further testing reveals 30p is fine, 24p is fine, it's just 29.97 that's causing me the issue

Did you try 23.976? Just curious. 29.97 has a drop-frame and non-drop-frame variant but I didn't notice whether the BMD Camera App has a setting for this. Not that DF vs NDF should matter to the duplicate frame issue, one wouldn't think (I believe it's only an interpretation of the timecode but I could be mistaken).
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Chris Nielsen

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Re: Weird duplicated frame problem with BM Camera app 1.2

PostSun Dec 10, 2023 7:48 pm

I hadn't so I just tried it now. In a totally unsurprising turn of events, 24 was fine but 23.976 had one extra frame every 24 frames.
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Re: Weird duplicated frame problem with BM Camera app 1.2

PostSun Dec 10, 2023 10:23 pm

Oh no!
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Re: Weird duplicated frame problem with BM Camera app 1.2

PostSun Dec 10, 2023 10:25 pm

I've been using Resolve for years, used to own a BMPCC and I think I've got a good basic grasp of how this stuff works but it's entirely possible I've made some grievous error and there's nothing wrong with it!
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Re: Weird duplicated frame problem with BM Camera app 1.2

PostMon Dec 11, 2023 2:12 am

I can reproduce that issue here, if set to 23.98 the app is actually recording 23.001 only!
If you drop such footage into a 23.98 timeline and have your retime setting on Nearest, DR will add one frame every second.
Since I see the same behaviour with recordings from Cinema P3 Camera, this might be a bug in iOS and not the individual app.
Maybe AI can help you. Or make you obsolete.

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Chris Nielsen

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Re: Weird duplicated frame problem with BM Camera app 1.2

PostMon Dec 11, 2023 2:14 am

Good to know I'm not going quietly mad here.

Next question: How do we escalate this to BM to look at?
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Re: Weird duplicated frame problem with BM Camera app 1.2

PostMon Dec 11, 2023 3:04 am

I have exactly the same issue. Driving me crazy. FCPX doesn't seem to have this problem, strangely, with the exact same clips.
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Uli Plank

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Re: Weird duplicated frame problem with BM Camera app 1.2

PostMon Dec 11, 2023 3:38 am

I'm pretty sure they are looking at this:
viewtopic.php?f=2&t=188344
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Shrinivas Ramani

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Re: Weird duplicated frame problem with BM Camera app 1.2

PostMon Dec 11, 2023 8:41 am

Hi Chris

Can you set a specific shutter value (not auto) and capture in 23.97 or 29.98 fps to see if the issue still persists?

Thanks
Shrinivas
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Uli Plank

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Re: Weird duplicated frame problem with BM Camera app 1.2

PostMon Dec 11, 2023 11:10 am

With a fixed shutter angle it's recorded as 23.98 fps (between 23.971 and 23.990).
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Re: Weird duplicated frame problem with BM Camera app 1.2

PostMon Dec 11, 2023 12:48 pm

Uli Plank wrote:With a fixed shutter angle it's recorded as 23.98 fps (between 23.971 and 23.990).


Problem is, that when you lock the angle in BMC, the ISO value becomes fixed too; it stays glued to the automatically selected value when locking 180 degrees. Wither that was 5x, 5xx or 5xxx ISO, that value remains on screen (at least for me).

Same effect with fixed shutter selection (instead of angle).

I haven”t checked, whether the material actually recorded is using “auto iso”. There is NO option to set ISO to AUTO mode either, when shutter/angle is locked. The option could be handy in some situations.

In Cinema P3 set to Shutter Priority mode (in contrast to fully manual), ISO is adjusting as would usually be expected.

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Re: Weird duplicated frame problem with BM Camera app 1.2

PostMon Dec 11, 2023 12:56 pm

Uli Plank wrote:I can reproduce that issue here, if set to 23.98 the app is actually recording 23.001 only!
If you drop such footage into a 23.98 timeline and have your retime setting on Nearest, DR will add one frame every second.
Since I see the same behaviour with recordings from Cinema P3 Camera, this might be a bug in iOS and not the individual app.

I can't reproduce this with my iPhone 12 Pro Max, iOS 17.1.2. I took some footage @23.976 UHD and then dragged that into Resolve for the iPad (on a 23.976p timeline) and then stepped through. The footage was a continuously moving subject. The subject moved in each frame.
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Re: Weird duplicated frame problem with BM Camera app 1.2

PostMon Dec 11, 2023 2:26 pm

Can you please check the fps values with MediaInfo, Steve?
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Re: Weird duplicated frame problem with BM Camera app 1.2

PostMon Dec 11, 2023 2:42 pm

Uli Plank wrote:Can you please check the fps values with MediaInfo, Steve?


Video
ID : 1
Format : HEVC
Format/Info : High Efficiency Video Coding
Format profile : Main@L5.1@Main
Codec ID : hvc1
Codec ID/Info : High Efficiency Video Coding
Duration : 8 s 176 ms
Bit rate : 35.8 Mb/s
Width : 3 840 pixels
Height : 2 160 pixels
Display aspect ratio : 2.35:1
Frame rate mode : Variable
Frame rate : 23.976 (23976/1000) FPS
Minimum frame rate : 23.962 FPS
Maximum frame rate : 23.990 FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Bits/(Pixel*Frame) : 0.180
Stream size : 34.9 MiB (98%)
Title : Core Media Video
Encoded date : 2023-12-11 04:10:29 UTC
Tagged date : 2023-12-11 04:10:37 UTC
Color range : Limited
Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.709
Codec configuration box : hvcC
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Re: Weird duplicated frame problem with BM Camera app 1.2

PostMon Dec 11, 2023 5:04 pm

Steve Alexander wrote:
Uli Plank wrote:I can reproduce that issue here, if set to 23.98 the app is actually recording 23.001 only!
If you drop such footage into a 23.98 timeline and have your retime setting on Nearest, DR will add one frame every second.
Since I see the same behaviour with recordings from Cinema P3 Camera, this might be a bug in iOS and not the individual app.

I can't reproduce this with my iPhone 12 Pro Max, iOS 17.1.2. I took some footage @23.976 UHD and then dragged that into Resolve for the iPad (on a 23.976p timeline) and then stepped through. The footage was a continuously moving subject. The subject moved in each frame.


The iPhone 12 Pro doesn’t produce ProRES (mine doesn’t).

If the h265 codec (and probably the h264 too) uses long GOP, chances are, that you would not experience anything untoward.

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Re: Weird duplicated frame problem with BM Camera app 1.2

PostMon Dec 11, 2023 6:18 pm

I expect that generating H265 HEVC on-the-fly would be much harder than ProRes in terms of processing power. True that ProRes has a much higher bandwidth, but is also much easier to generate. Anyway, I don't see the issue with the iPhone 12 Pro Max. For those who see it, try switching to H265 HEVC and see if that corrects the issue. This could be an iOS / iPhone 15 issue...
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Re: Weird duplicated frame problem with BM Camera app 1.2

PostMon Dec 11, 2023 11:15 pm

Steve Alexander wrote:I expect that generating H265 HEVC on-the-fly would be much harder than ProRes in terms of processing power. True that ProRes has a much higher bandwidth, but is also much easier to generate. Anyway, I don't see the issue with the iPhone 12 Pro Max. For those who see it, try switching to H265 HEVC and see if that corrects the issue. This could be an iOS / iPhone 15 issue...


It’s probably not a performance problem per se.

Look at the frames per second specifications (using milliseconds as time basis):

Problem childs

Blackmagic Camera selection (not selectable in Apple Camera):
24000/1001, 30000/1001 and 60000/1001 (are they all affected?)

Not problematic:

Official Apple Camera selection options:
24000/1000, 30000/1000 and 60000/1000
Apples official PAL based options:
25000/1000

It probably has nothing to do with “system stress” as such. The "pure" 60 fps (60000/1000) ProRESHQ (~1.5-1.6 Gigabit/sec) does not seem to be affected, but certainly requires far more umpffh, than 24000/1001 fps any day (not to mention the around 25 megabit/sec required for a completely different h265 group/block based codec on iPhone 15 Pro or iPhone 12 Pro).

My guess is, that BlackMagic either has a slight error - a kind of “logic disconnect” or “configuration error” in BMC’s “handling” system, or they’re using options, not guaranteed by Apple or… or… it may even be Blackmagic being a bit optimistic on delivery of frame settings, compared to some Apple “recommended settings”.

Possibilities are many in this case. Only actual code and log inspections, maybe even hardware timing checks, will be required to find the basic, real cause behind the problem.

I’m not trying to blame anybody, just looking for a possible (!!!) cause, without access to code, underlying requirements and whatnot. The actual cause may - as is VERY often the case in real life bug hunting - end up as a simple "Awww, is that really just... sigh!" problem, when finally spotted!

Regards
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Re: Weird duplicated frame problem with BM Camera app 1.2

PostMon Dec 11, 2023 11:37 pm

Have you tried recording HEVC to see if the duplicate frame issue is still evident on your iPhone?
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Re: Weird duplicated frame problem with BM Camera app 1.2

PostMon Dec 11, 2023 11:44 pm

Steve Alexander wrote:Have you tried recording HEVC to see if the duplicate frame issue is still evident on your iPhone?


First thing I tried, issue still persists
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Re: Weird duplicated frame problem with BM Camera app 1.2

PostMon Dec 11, 2023 11:46 pm

Shrinivas Ramani wrote:Hi Chris

Can you set a specific shutter value (not auto) and capture in 23.97 or 29.98 fps to see if the issue still persists?

Thanks
Shrinivas


Just coming back to this, since it was posted after I went offline last night. I just tried it now, locking a shutter value appears to eliminate the problem, it's when I am shooting in Auto is where I see the issue.
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Uli Plank

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Re: Weird duplicated frame problem with BM Camera app 1.2

PostTue Dec 12, 2023 1:06 am

Now, that’s why I didn’t notice earlier. I tend to fix shutter to 180 degrees and expose by ISO and ND only, because I hate that stuttery action cam look.
But if we can observe that bug in Cinema P3 too, so it might be an iOS issue.
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Chris Nielsen

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Re: Weird duplicated frame problem with BM Camera app 1.2

PostTue Dec 12, 2023 1:09 am

Uli Plank wrote:Now, that’s why I didn’t notice earlier. I tend to fix shutter to 180 degrees and expose by ISO and ND only, because I hate that stuttery action cam look.
But if we can observe that bug in Cinema P3 too, so it might be an iOS issue.


Care to share any recommendations for NDs or VNDs for iphones?
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Re: Weird duplicated frame problem with BM Camera app 1.2

PostTue Dec 12, 2023 1:16 am

Steve Alexander wrote:Have you tried recording HEVC to see if the duplicate frame issue is still evident on your iPhone?


I can duplicate the following:

Black magic screen lets me select: 59,94 fps

Media Info:

com.blackmagic-design.sensorFPS : 59.94
(what Blackmagic assumes is requested. Whether true or not, can only be established by looking at the actual code)

Extracted data (probably set by Apple):

    Codec-ID/Info : High Efficiency Video Coding
    Varighed : 2sek. 272 ms
    Bitrate : 55,9 Mb/s
    Bredde : 3.840 billedpunkter
    Højde : 2.160 billedpunkter
    Størrelsesforhold : 16:9
    Billedratemodus : Variabel
    Billedfrekvens : 58,976 FPS
    Minimum billedfrekvens : 58,881 FPS
    Maksimum billedfrekvens : 59,055 FPS

Seems very similar to a request made for 59000/1001 fps. Doesn't it?

Timecode specifies: 59,940 (60000/1001) FPS

The delivered value is set to: 58,976 fps. (very close to 59000/1001).

Now, what can I deduct from this?

That may be true, but is it what, Blackmagic requeested as "RECORDING FPS" in the actual code? How do I know? (it's not unusual, that one field is based on a text string, and the actual request based on some numerical value or even an "enumeration" (a logical term repesenting an index into a table). You can alter one, without affecting the other. An extremely common error in coding.

Blackmagic lets you select 59,94 fps, and use the same text (not a calculated value?) in their metadata part of the MOV file header.

Do they request 59000/1001 (or a buggy calculation returning that value) in their actual code or the correct 60000/1001 (which need not be directly linked to the values presented on screen, or in the metadata or timecode spec).

Alternative possibility: Values obtained from an Apple include file are problematic, but then it would be more than unusual, that the same include file produces different values in iPhone 12 Pro.

An Apple firmware problem (in iOS 17.x). Possible. If it is a "hardware bug" we're in trouble. Hope not.

How come all the xx/1001 fps specs are affected, and NOT the xx/1000 fps?

How am I to decide, if Blackmagic has introduced a simple notational/computational error or if they play "fast and loose" with the actual recommended (or "allowed") options (assuming, it may work anyhow), or if it as error in unofficial Apple options?

Blackmagic initially also allowed the use of ProRES 4444 (which Apple probably does not support officially), which had weird side effects in some combinations, I tried. Was this a case of "maybe it works anyway", or some beta code, that was erroneously included in the release code? How do I know? Blackmagic is more or less "mum" on that little episode.

As I said: It's probably a simple programming error or use of undocumented, unsupported or non-recommended settings. Otherwise, it would be naturally to assume, that the exact 24, 25, 30 and 60 fps also deviated by exactly 1 frame per second. Why not 23 instead of 24, 24 instead of 25, when we end up with 28.97 instead of 29.97)? Just asking.

For 30000/1001 fps the values are:

Blackmagic metadata:

com.blackmagic-design.sensorFPS : 29.97

and Apple MOV-file content data:

    Billedfrekvens : 28,996 FPS
    Minimum billedfrekvens : 28,986 FPS
    Maksimum billedfrekvens : 29,014 FPS

Timecode frequency: 29,970 (30000/1001) FPS

Same question is: Does Blackmagic (by a simple notational/computational error) request 29000/1001 as recording speed? Do they request a "not recommended" or "not supported" speed of 30000/1001?

Obvious question: Does all xx/1001 fps settings end up more or less exactly one second lower (makes no sense, but... in bug-country, anything goes; doesn't have to make sense in real life)

Next obvious question: Does none of the xx/1000 fps settings end up as minus 1 second?

I generally work with 25fps, and I certainly do not get in the region of 24 fps delivered. I get (recent example):

    Billedfrekvens : 25,000 FPS
    Minimum billedfrekvens : 24,969 FPS
    Maksimum billedfrekvens : 25,052 FPS

and timecode: 25,000 FPS

That's as expected.

Blackmagic is still a fairly recent release, and even in far more "mature" App's "old bugs" surface from time to time. Without looking at the code, I have no way to decide, what is going on in real life in the code (if deviating from what is supposed to happen in the code).

Last question:

Does the iPhone 12 Pro get the same code delivered as iPhone 15 Pro? Or is the code to large parts identical, where the App switches between "tables" (to avoid another more long and windy explanation)? If so, are the contents of these tables identical for options supported by boot phones? And so forth...

The devices are obviously not identical. The obviously do not have the same capabilities. It happens, that I accidentally look for ProRES settings on my spare iPhone 12 Pro (now, they have different colored cases ;-)

I can confirm, that there are systematic differences on the iPhone 15 Pro for all HEVC xxxxx/1001 based frame rates shown above. And not for xx/1000 based frame rates I have tried (not all presented).

Does that also apply to iPhone 14 Pro (luckily I do not have that one, so you'll have to pester another user ;-)

And now I'm off to bed. It's way past normal bed time!

Regards and a big smile
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Uli Plank

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Re: Weird duplicated frame problem with BM Camera app 1.2

PostTue Dec 12, 2023 2:13 am

Chris Nielsen wrote:
Uli Plank wrote:Now, that’s why I didn’t notice earlier. I tend to fix shutter to 180 degrees and expose by ISO and ND only, because I hate that stuttery action cam look.
But if we can observe that bug in Cinema P3 too, so it might be an iOS issue.


Care to share any recommendations for NDs or VNDs for iphones?


If you don't mind, I'll take this discussion over to the right thread:
viewtopic.php?f=2&t=191338&start=150#p1005945
Last edited by Uli Plank on Tue Dec 12, 2023 2:32 am, edited 1 time in total.
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Re: Weird duplicated frame problem with BM Camera app 1.2

PostTue Dec 12, 2023 2:29 am

Addendum on possible bugs

How do you end up with the described problem (example: 29000/1001 instead of 30000/1001) in your code? One possible example:

Old code:

Value = 23.998; // fps

New code (steps to completion)

1. Step: delete 998

Value = 23; // fps

2. Step: add 000/1001

Value = 23000/1001; // fps

3. Step: Forgetting to alter 23 to 24.

Value = 23000/1001; // fps

Hastily assume "COMPLETED".

4. Step: SLAM! Check into code repository
5. Step: Forgetting to check actual delivered MOV file format (MediaInfo comes to mind)

This is purely hypothetical and involves two extra - unlikely - similar approaches for 29.997 and 59.994 fps values, but it is NOT impossible, if a programmer stresses to get code finished to an exhibition, presentation or release. More probable some "buggy" automated replacement routine is used (altering ".99?" text sequences into "000/1001" text sequences. Result the same in all three cases. Similar approaches have been seen... a lot! ;-).

That’s at least my experience as - also - seasoned bug hunter over more than thirty years (own and other code) before retirement.

General view: Check, check again, even if it’s improbable; check!

Most bugs I have found, where positioned squarely in code (own or other origin), where it was assumed completely impossible to do something wrong. Alas… real world code, does sometimes behave in clearly “impossible” ways - for some “impossible” reason ;-)

Regards and reme....
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Re: Weird duplicated frame problem with BM Camera app 1.2

PostTue Dec 12, 2023 8:56 am

iOS 17.2, Sonoma 14.2 and Xcode updates released this morning

This morning there were updates to Sonoma 14.2 and iOS17.2 as well as updates to Xcode (command line tools).

The iOS update officially includes modifications to the camera,

On the ‌iPhone 15 Pro‌ and Pro Max, the Telephoto camera now focuses faster when capturing small, faraway objects.

Includes support for spatial video.

Plus this sorely needed message concerning the use of the standard USB-C cable included in the iPhone box. Quoting “Macrumors”:

Recording to an External Device:
With the ‌iPhone 15 Pro‌ models, ProRes video can be recorded directly to an external device. iOS 17.2 appears to include a new pop up message that lets users know that external recording is not working because of a USB-C cable that is too slow.
There was previously a warning about an external storage device not having a fast enough write speed to support external recording, but now there is an added message about the write speed of the USB-C cable.

29.97 fps short test on iOS 17.2

A quick test of BMD at 29.97 fps (h265) on my iPhone 15 Pro showed:

    Billedfrekvens : 28,995 FPS
    Minimum billedfrekvens : 28,972 FPS
    Maksimum billedfrekvens : 29,014 FPS

In other words, nothing changed on that front.

End of report.

Comment

Since I do not use 24000/1001, 30000/1001 and 60000/1001 fps, I’ll not be part of any future bug hunting on that front.

Regards

Added: If the field specifying frame rate has been altered from “float” to “integer” in iOS17 for iPhone 15 Pro (Max), the behavior is consistent with 30000/1001 = 29.97 fps being truncated to nominally 29 fps!
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bailaowai

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  • Real Name: Eric Esser

Re: Weird duplicated frame problem with BM Camera app 1.2

PostTue Dec 12, 2023 9:40 pm

I have the sense, and I could be wrong, that it has something to do with variable frame rate handling. It could be as simple as Davinci Resolve not respecting variable frame rate. Maybe?

Because . . . all my footage which I recorded iPhone 15 pro max in 59.94 but which shows us as 58.776 or something in media info has duplicated frames in davinci resolve, but DOES NOT HAVE DUPLICATED FRAMES in FCPX. Now my problem is that I don't want to use FCPX, I want to use Davinci Resolve.

I rendered clips from FCPX to ProRes HQ to 59.94 and the duplicated frame issue is gone (and the file goes from variable frame rate to constant frame rate)

I also used compressor to basically transcode all my 59.94/58.776 variable files that I got from BMD camera app on iPhone 15 pro max to 59.94 constant frame rate and these also work fine in davinci resolve. I do not notice any artifacts of the transcode (sync issues or stuttering or anything else). So for now this is for me a workaround, although it adds time for the transcode before using the files. I still prefer this + Davinci Resolve to the alternative of using FCPX.
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Uli Plank

  • Posts: 20691
  • Joined: Fri Feb 08, 2013 2:48 am
  • Location: Germany and Indonesia

Re: Weird duplicated frame problem with BM Camera app 1.2

PostThu Dec 14, 2023 6:03 am

What is your setting for retiming in either NLE?
Maybe AI can help you. Or make you obsolete.

Studio 18.6.5, MacOS 12.7.3
MacBook M1 Pro, 16 GPU cores, 32 GB RAM and iPhone 15 Pro
Speed Editor, UltraStudio Monitor 3G, iMac 2017, eGPU

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