Ghost Frames Explained (maybe)

johnmeyer wrote on 3/4/2014, 7:01 PM
There were two recent, very long threads about ghost images in rendered output:

Ghosted Images on DVD but nowhere else

and

Those Ghost Images (continued) and FX connections

In that second thread, I describe how this problem can be created if you put certain types of MPEG-2 files on the Vegas timeline. This is especially true of some types of VOB files that some people copy directly from the DVD. What happens with these files is, that as you scrub back and forth across the timeline, Vegas gets "confused" and starts serving out frames in the wrong order. This shows up not only on the timeline, but can carry through to the final render. I realize that in those threads, the OP said that the timeline playback looked fine, but I'll bet that there was still some sort of weirdness going on.

About five minutes ago I was in a hurry, and rather than get the files onto my hard drive from the DVD in one of the "right" ways, I simply copied the VOB to the hard drive and then put it on the Vegas timeline. As I scrubbed the timeline, I saw the same effect as seen in the sample file provided in the second thread above. I then rendered to MPEG-2 using the standard DVDA template, and this is the result:

Test Clip.mpg

Looks familiar, eh?

This was 24 fps film that had been hard-telecined to 29.97 (i.e., the pulldown fields were actually encoded, rather than instead encoding only the 24 fps film and then setting the DVD pulldown flag).

This test was done in Vegas 8, and I am sure that Sony has made many changes to the underlying structure of the program since that long-ago version. However, I think far less work has been done to change or improve the reading of SD MPEG-2 files, while more work has gone into HD m2t, AVCHD, and H.264. Therefore, it is possible that this same behavior is still latent in the current (V12) versions of the program.

So, the point of the post is that if you see this problem, then you may want to pay more attention to how you copy/acquire the video and, if necessary, you may want to use another program to convert that video into Cineform or MXF or some other intermediate before you put it into Vegas.


Comments

set wrote on 3/4/2014, 9:22 PM
DVD or MPEG2 files* can happen like this, exactly.
*From Sony's avchd camcorders, where still have the capability of recording in SD 480/60i or 576/50i.

Not just make ghost images, but if you have a lot of these media files, Vegas Pro is also getting 'heavy' and 'tired', and can lead to unavoidable crash, every time you want to open project.

I usually convert these files first into AVI DV via Ultimate S Pro batch render.

If you need to render straight from edited VOB / MPG2, close Vegas Pro first, reopen again, and proceed with render straight (without scrubbing - just don't 'touch' them!).


Set
paul_w wrote on 3/5/2014, 3:14 AM
That certainly looks similar John! Must say well done for recreating would could be the issue.
But as a note, while seeing frame flashing exactly like the thread 2 test footage, i'm not seeing the actual 'ghosting' element here.. ie.an image over another image.
Any idea why that could be?

Paul.
Richard Jones wrote on 3/5/2014, 8:51 AM
John

That's really fascinating and quite remarkable and worth bearing in mind for all of us.

It still doesn't explain away my problem as my source was AVI 25fps loaded straight on to the Hard Drive from the Telecine conversion of the Standard 8mm cine film so I don't think a VOB transfer can have taken place and MPEG2 only came into the equation when I did my own render at the end of the project.

Even so, it does seem that, in some circumstances, there is a problem within Vegas which is causing some sort of ghosting to take place on the Timeline. Interesting.

Richard