Notes on Black Frames in Captured Video

Bill Ravens wrote on 12/13/2007, 9:56 AM
I apologize ahead of time if this information has already been discovered and posted in this forum.

I've been tracking down the source of black frames and capture problems encountered with HDV video streams. I'm working with a JVC HD110 HDV cam and Sony Vegas 8a. I've been encountering black frames, seemingly randomly, when importing m2t files to the Vegas timeline, but, not if the m2t files are first converted to Cineform Intermediate files before importing.

As it turns out, the black frames aren't random. While I'm shooting tapeless, ie to an external hard drive(nNovia), I will pause recording for a scene change. During the pause, timecode continues to accrue in the DTE device, even tho' the camera has been paused. Since there is no TC signal from the camera in tapeless operation, TC is being generated externally in the DTE device and recorded to the m2t file. After the pause, and I return to recording, the new scene is appended to the original file, however, since TC has continued to accrue, there is a sudden jump in recorded TC. The jump is equivalent to the time I spent in pause.

When the m2t stream is imported to the timeline, Vegas sees the TC jump and has a great deal of trouble dealing with the discontinuity. Black frames seem to be the result. Conversion to a Cineform Intermediate with HDLink avoids this problem because every scene change in a contiguous file is written out to a new video clip, hence no jump in TC within any clip.

I've filed a ticket with tech support over this issue. Feedback from the DTE device maker claims the problem isn't theirs.

Comments

farss wrote on 12/13/2007, 10:25 PM
Bill,
I doubt it's the break in TC. Vegas seems to happily ignore TC. I once had a problem tape with TC coming and going all over the place and Vegas didn't have a problem with it. However I have much similar problems to what you're describing.

1) Copy .vob files from a DVD and drop them onto the TL. Where they join you'll have issues. Using DVD Shrink to join them into one giant .vob, no problem.

2) Using DR60 HDD recorder on V1 for long concert where the m2t files are split by the FAT32 limitation and simply trying to join them up on the T/L, same problem at the join. Using Import HDD option they get joined onto my local HDD as one m2t file and then no problem.

I suspect your problem relates to what the recorder does when it's in pause and how Vegas handles that.

Bob.