mpg render comes out 4seconds shorter than project

earthrisers wrote on 9/25/2008, 6:20 PM
Hee's one I've never encoutered before...
I've got a project (regular DV format) that is exactly 58 minutes, 30 seconds long -- the length that's required for submitting a program to local cable television.

When I render to mpg in preparation for making a DVD, the resulting mpg is 58 minutes, 26 seconds, 15 frames long.
I rendered DVD Architect NTSC stream, and Dolby Pro ac3.

This discrepancy of length has never happened to me in previous projects. Anyone have a clue as to what happened to my 4 seconds?
The video and audio fade-out at the end of the program looks/sounds the same as in the original project, so it's not a matter of the 4 seconds being truncated from the end...

Comments

robwood wrote on 9/25/2008, 6:59 PM
maybe a 29.97 vs 30fps mix-up?
Chienworks wrote on 9/25/2008, 7:14 PM
That sounds like exactly what it is. 29.97002997 vs 30fps comes out to match that length to within 0.2 frames.

I'm guessing the MPEG file is the correct number of frames but whatever you're playing it back on thinks it's 30fps instead of 29.97002997. Perhaps the gspot program can verify what frame rate is embedded in the file. Try playing it with some other software and see it's the same length there.
johnmeyer wrote on 9/25/2008, 10:13 PM
Well, everyone liked my math yesterday, so to add to what Kelly and Rob said:

58 minutes, 30 seconds = 3,510 seconds
58 minutes, 26 seconds, 15 frames = 3,506.5

3,506.5 / 3,510 = 0.999002849

OK, so much for that.

Now, the ratio of 29.97 (approximately) to 30.00 is actually determined exactly by this ratio:

1000 / 1001 = 0.999000999

The difference between these two numbers is within 0.00018 %, or as we say around here, close enough for government work (actually these days in the USA, anything within $100 billion is close enough, but don't get me started ...).

So I think that the problem is exactly as already stated: either the render was done using the wrong template and has been done at 30 fps instead of 29.97, or else you have a player that is reporting back based on 30 instead of 29.97.

My suggestion is to download the free GSpot utility and drop the MPEG-2 file on that. It will instantly tell you whether it was encoded for 29.97 or 30.0.


Former user wrote on 9/26/2008, 8:04 AM
The math is working for 30 vs. 29.97 but it could also be a NDF vs. DF timecode issue. Depending upon how you are judging the length of the program.

If your VEGAS timeline is set to show NDF SMPTE timecode, then the reported program length and the actual program length will differ, usually about 3 seconds per hour (although you can figure it out exactly mathematically). The best way to check is to change your timeline to DF SMPTE timecode and see what the reported length is.

Dave T2
earthrisers wrote on 9/26/2008, 11:17 AM
Additional info as of this morning:

GSpot confirms that my rendered MPG file is 29.97fps, and that its duration is 58:30.

I then changed the timeline time-format in Vegas from DropFrame to NonDropFrame, and the end-of-file time now agrees exactly with what I'm seeing in DVD Architect - the duration shows 58:26:15.
(Which means that the Vegas duration-display in this format does NOT agree with what GSpot says is the duration of the MPG file I rendered earlier.)

I don't see any DropFrame versus NonDropFrame setting in DVD-Architect.
How do I "make" DVD-A agree with what GSpot says, and make a DVD that is 58:30 in duration?
Or do I need to change something in Vegas, and re-render to MPG?
Or...?
I've produced a few hundred DVD projects with Vegas/DVD-A, but haven't run across this issue before, so I'm trying to work my way out of being baffled...





Former user wrote on 9/26/2008, 12:37 PM
Right click on the DVDA Timeline where the frames and seconds are (the time ruler) and see what that is set for.

Also on the DVDA timeline, if you put the cursor on the last frame of VIDEO what time is it reporting?

Dave T2
earthrisers wrote on 9/26/2008, 12:46 PM
Ah!

I had been right-clicking in DVD-A on the bold Time Now display, instead of on the Time Ruler in the timeline.

Now I right-clicked in the time ruler, and the format was set to SMPTE (I don't recall ever setting that, but I guess I must have).

I changed it to "Time and Frames", and now it shows 58:30:00, which is exactly what I want.
If I'm not mistaken, the DVD I create will in fact be 58:30:00 "clock time"... just right.
Thanks much!