video lag

kulinek · Post by **kulinek** » Wed Apr 13, 2005 7:59 pm

I know that there was a audio lag topic. What I am getting however is that audio comes first and then video. The original MPEG is over 1G and A/V is in sync. I loaded the mpeg in and then I saved it with different options (changed from fieldA to fieldB) the resulting mpeg has video lag. I played mpeg off the HD.

I tried with TMPGEnc demultiplex and Restream to reverse field, back multiplex with TMPGEnc, the problem occurs as well. The lag is visible on the larger MPEG like 1G.

The original mpeg was recorded with UVS v7 with fieldA. I realized that it should have been fieldB.

Any ideas why this happens?

THoff · Post by **THoff** » Wed Apr 13, 2005 8:54 pm

My guess is the video was recorded at 30fps instead of 29.97fps. Is the audio seemingly in sync initially, and then slowly drifts further and further out?

kulinek · Post by **kulinek** » Thu Apr 21, 2005 10:03 pm

Good guess. Quite possible that this difference between 29.97 vs. 30fps could cause the video lag. As the original mpeg was in ok, then saving it with the reversed field must have been done with 30fps. THe Properties, however, indicates 29.97fps but maybe it is incorrect. Actually, UVS7 gives no option of which fps I want - it is always 29.97.

I have done little estimation what would be the lag on 60,000 frames - I recall coming up with 2sec lag at the end of mpeg which is close to what I am getting.

I guess the bottom line is why UVS7 would use 30fps when reversing the fields and not otherwise. Maybe TMPGEnc has options that can specifiy what fps I want when multiplexing m2v with mp2.

Regards
Eugene

THoff · Post by **THoff** » Thu Apr 21, 2005 10:22 pm

How did you save the MPEG file in UVS?

I would not use the existing templates that are offered when you choose "Create Video File", I would choose "Custom" at the bottom of the list, set the format to MPEG, and then customize the settings using the "Options" button in the dialog. That will give you complete control (well, as much control as UVS allows) over the MPEG file properties.

kulinek · Post by **kulinek** » Fri Apr 22, 2005 5:47 pm

I do use Custom setting when saving MPEG, the only thing I change there is the field order (from fieldA to fieldB). All other settings are the same as the original mpeg. In the dropdown for fps there was only a single choice 29.97.

Just to be sure at this point I have an mpeg that I load in and then save with that small change (field order). Also, I have a single project with all the default settings, I load it in as soon as I start VS7. I use the same settings for all my home videos.

Eugene