Video dropped frames but audio continuous

[Michael Blieden]

Anyone ever experienced this? Shooting a documentary last week with my Epic Dragon (loooong continuous takes). Never had a problem except for one clip, where about 3 seconds of video disappears in the middle of the clip, it's almost like I did an edit in camera. But the audio recorded continuously, so from the point of the glitch onwards for the rest of the clip the video is 3 seconds ahead of the audio.

My Offload (checksum) software was not able to copy the full clip, but I was able to export audio and video through Red Cine by creating a new clip with an in point after the glitch. I'll shift the audio in the edit.

I remember fiddling with the xlr inputs on the wireless lav system while I was rolling, right around the time that this happened, but can't say for sure if it was exactly where the glitch is. Whenever fiddling like this there is always a spike in the audio signal. I'm wondering if that spike can temporarily f*** with the signal path of the video? Just a theory.

I put that Redmag aside, planning on digging out some drive diagnostic software to test the sectors on the mag, haven't used it since. In the meantime wondering if there's any other known instances of this.

 

[Marcus Friedlander]

I've never heard of that but it sounds scary! Was your dropped video exactly 3 seconds? Like on the dot? Or was it more like 2 seconds and 20 frames? If it was exactly 3 seconds I have a feeling it could be something worse than if it was just roughly 3 seconds.

Either way, I would absolutely send a LOG file over to RED and have them take a look at it. RED takes data integrity very seriously. I'm sure they would very much like to solve this problem as well!

 

[Todd T]

Does the last frame before the glitch match up with the first frame after the glitch?
And you were able to open and export the clip in REDCine-X, but not able to copy it via your offload application?
What were you using to offload?

This is an interesting situation
If it was just dropped frames then the audio would still be in sync.
With the delay, it looks like the video processing path temporarily hung while the audio processing path continued on.

 

[Michael Blieden]

Was your dropped video exactly 3 seconds? Like on the dot? Or was it more like 2 seconds and 20 frames?

3 seconds is only a rough guess, but it's definitely more than just a few frames. When I get into editing I can figure out what the exact offset is by resyncing the audio after the glitch. I'm just not there yet.

I could send a log file but I've shot several hours of footage since then with no problems. I'm wondering if it would still show up as an anomaly. I guess that's a question for tech support.

 

[Michael Blieden]

Does the last frame before the glitch match up with the first frame after the glitch?

No it they don't match. From a video perspective it's as if there was an edit, like a jump cut.

And you were able to open and export the clip in REDCine-X, but not able to copy it via your offload application?
What were you using to offload?

I was using Red Giant Offload and this clip produced an error in Offload. The glitched clip was from a long take there were 11 4Gig segments in total. Offload copied the first but 7 would not copy the 8th 4gig segment with the glitch in it. If memory serves it then continued offloading with the 9th clip.

I was able to export the missing segment in Red Cine, however I could not export it as an entire clip. I had to set an in point after the glitch and export the remainder as a separate clip.

What's worth noting here is that the missing seconds are critical to my story (remember this is doc, so I couldn't restage). And as I see it, it's not a coincidence that the glitch happened at a key moment. I knew as I was filming that I had just gotten a sound bite I had been waiting for, so I self-consiously reached up and adjusted the input level on my wireless XLR receivers. This jiggled them in the sockets on my Pro I/O and that's when the big audio spike happened (as it always does when you fiddle with XLRs.) What's important is that the audio is all there, and the missing seconds of video are something I can easily cut around. To me it's a lesson in staying calm when an important moment happens and to not start blindly groping around to adjust things.

it looks like the video processing path temporarily hung while the audio processing path continued on.

Yes exactly. That's precisely what it feels like to me.

 

[Maz Mawlawi]

Had the exact same thing happen 5 months ago on a shoot.
We reused the same mag on other shoots with no problems and never had the glitch again....(i know...its not very helpful)

 

[Michael Blieden]

Had the exact same thing happen 5 months ago on a shoot.
We reused the same mag on other shoots with no problems and never had the glitch again....(i know...its not very helpful)

It is helpful actually. I feel like it's just a thing that happened.

I put a red sticker on the mag and see if it ever happens again.

 

[Marcus Friedlander]

To me it's a lesson in staying calm when an important moment happens and to not start blindly groping around to adjust things.

Well put! Definitely an important lesson for all of us to learn. Happy to hear that it didn't ruin your edit though!