Shouldn't the 24p file be smaller?

William_Robinette

William_Robinette

Shallow Member
Ok so I was testing some stuff out today. I know it has been said that if you burn a 24p DVD, you should be able to fit more footage onto it do to you encoding only 24 frames and not all 30. Now in my mind this would make the file size smaller.

I output a 24p clip and a 30p clip from Vegas (mpeg2) and they are both the same size on my disk, and my DVD-A project. Now, when I take the 24p and 30p .avi files into DVD-A, I am seeing the file size difference. My 24p mpeg out of Vegas is obviously in a 29.970 stream.

Why can I not encode a 24p mpeg2 file out of Vegas (or so it seems)?
 
Everything was the same as that template except that I encoded with a 8,000kbps CBR.

And the only difference between the 24p and the 30p renders was of course, the two different frame rates. Both were at 8,000kbps CBR
 
Try encoding as 60i and see what you get . . .

Try encoding a 24p MPEG without the "+2:3 Pulldown" option. Let me know what you get.
 
Wow, I never realized there was a 23.976 sans pulldown before...

but still, I did the renders as you said, David, and the file size on the disk is still the same, but I am seeing a difference in my DVD-A project (not a big one, 2mb over a 1:30 clip)

These are my render parameters.
24p
1180396997.jpg


30p
1180397140.jpg
 
I'll have to try to replicate the problem later. In the meantime, experiment a little and see if you get the same results when using VBR.
 
Maybe I'm missing something, but if you render at 8000kbps CBR for both, then they'll both use the same data rate, and therefore end up the same size. Why would they differ if you set the rates the same? the 24p will however have more bandwidth available per frame than the 30p version, so in theory the 24p version should look very slightly better at a fixed data rate.

VBR = "use as much bandwidth as you need at any given point in time in order to reach a fixed level of visual quality" ... in this case, the 30p version will need more bandwidth to retain the same level of quality, so I'd expect the final file to be a little bigger.
 
I believe that's accurate (which is why I wanted BennisHahn to try it), but I wasn't 100% certain of it with MPEG-2 and DVD.
 
I rendered a file of mpeg2 which was size 1.3 gb. 2 such video files were rendered thru Vegas and dropped into DVDA. But in DVDA it says the files are much much bigger and have exceeded the capacity of a 4.7 gb dvd ??? How come ?
 
DVD-A has trouble counting at times.

Also: + audio, + menus

Also also: I'm pretty sure it needs at least twice the finished size to be available on the disk (for temporary files and such).

But it's probably a case of DVD-A not calculating properly.

I never burn from DVD-A. I prepare to hard drive and use Nero to burn. Bypasses all that nonsense, and I can see the actual finished size.
 
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