Corrupt Files

Hello,

Has anyone encountered purple corrupt files with their Blackmagic Pocket 4k? Weirdly, the audio in the corrupted files is perfectly fine. I really don't know where the blame lies; either the camera or the CFast card. I was recording to a ProGrade 512G CFast card. There was a microphone attached to the camera via mini-XLR.

It was a very strange occurrence as the first ten clips on the CFast card are corrupt (purple frame) but the remaining ten clips are perfectly fine.

I own two Blackmagic Pocket 4k cameras and the other functioned without issue. Would like to get to the bottom of this because I'm now leery about taking my cams on paid gigs.

Any help will be much appreciated.

Thanks,

Daniel

Do the purple files playback in the camera correctly?


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Never encountered that kind of corrupt before. Curious on what causes it.

Hey Rick,

The files play back in camera, however, the purple frame is visible. So, basically you'd be looking at a purple frame with some motion and hearing the audio.

Thanks,

Daniel

Daniel, that would seem to rule out any issue with a cable or card reader or related glitch so it would seem like your options are correct: card or camera? If it was related to a camera setting, it should be repeatable, but given you followed the purple frame clips with good frames, that also seems to eliminate a camera setting assuming you were using the same settings for the frames for bad and good clips. Since the good and bad frames were recorded with the same shoot and same conditions but the results are different, it may be difficult to reproduce if it was caused by a temporary glitch such as a poor internal electrical contact. That would be a serious issue as it could reappear and perhaps be persistent next time.

I would do a few things to remove any possible hardware or software issue except an intermittent electrical fault.

1) Reload the firmware for the camera.
2) Reformat the card in camera.
3) Try to repeat everything set or used when you had the problem including the same lens(es) if the lenses/adapters have electrical contacts.
4) Shoot with a cold camera in similar ambient conditions when you had the purple frames (which you normally would not do as it’s best to have the camera warmed up); playback each clip at least for a minute; continue to shoot short and longer clips until the card runs out of recording space.
5) Transfer everything to your computer to verify it’s all good in Resolve.

If all is well, it may be good to go again. Scary though to be confident for client work. If you can’t reproduce the problem, you’re never sure if it was software in the camera, circuits in the camera or card, a cosmic ray (that didn’t cause a permanent error).

Occasionally we see similar weirdness and it’s usually related to dropped bits from an unreliable cable or card reader and that’s normally proven when the card plays back in camera fine. So I’m thinking the temporary problem is a similar effect in recording. The cause may not be found if the result can’t be repeated. So continue to be cautious and review clips in camera.

If it doesn’t happen again, it’s a mystery but all may be well. I’d advise BMD Support that you have a potential flaw, but they may want you to return both the camera and the card, which isn’t always feasible. My gut feeling is that I’d keep the camera but not trust that card on a client shoot and send it back to the supplier for replacement hopefully. Sorry I can’t be more confident of the cause.



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