File size weirdness

billcoffin wrote on 7/3/2008, 1:33 PM
I have a project with two large mpg files totalling about 4.6 Gb. But DVDA 4.5 (the Studio version) shows them as being significantly larger. The playing time of the two files (according to Windows Media Player) is about 100 minutes.

So this should fit on a DVD, but DVDA says that I'm at about 140% of a DVD capacity, forcing me to compress. (The menu sizes are negligble.)

For instance, one file is 2.3 Gb but DVDA says it's 3.0 Gb! Does DVDA actually enlarge the files?

Comments

JohnnyRoy wrote on 7/3/2008, 7:11 PM
> I have a project with two large mpg files totalling about 4.6 Gb. But DVDA 4.5 (the Studio version) shows them as being significantly larger. The playing time of the two files (according to Windows Media Player) is about 100 minutes.

4.6 GB with just two files is too big. You have to allow overhead for the DVD structure itself and the menus. A single sided DVD can hold between 80 - 90 minutes of video at the standard 6Mbps bitrate. Any more than that and you need to start encoding a a lower bitrate.

> For instance, one file is 2.3 Gb but DVDA says it's 3.0 Gb! Does DVDA actually enlarge the files?

If the file contains MPEG audio it is probably calculating what it would take to translate that into PCM audio since MPEG audio is not part of the NTSC DVD specification. NTSC DVD audio can either be PCM uncompressed or AC3. I don't have the studio version so I'm not sure if it supports AC3 but if it does, that would be a better choice for your audio since it will be smaller than PCM.

~jr
TOG62 wrote on 7/3/2008, 11:05 PM
I don't have the studio version so I'm not sure if it supports AC3

It does.

Mike
MPM wrote on 7/4/2008, 8:56 AM
The size indication is off a bit - the only sure way I'm aware of is with all your files in 1 folder, check out the total size in Windows Explorer. OTOH, also check the File menu -> Optimize dialog... If your video is set to be re-encoded, the size shown can be quite a bit off as well.

If the total size of the files is larger than will physically fit on a DVD, you either have to use a bigger DVD (Dual layer instead of single), or re-encode 1 or more of your videos. The bit rate of an mpg2 file determines how large the file is - the duration of video is only a sort of guideline you can use planning your project. A single layer DVD can hold 1.5 - 1.75 of good quality video - for dual layer double that. You can fit more by reducing the bit rate or frame size, or you can increase the bit rate to the max (~9), plus have high bitrate AC3, & need a dual layer disc to hold 1.5 hours worth.

If you're already using DVD spec mpg2 (DVDA doesn't show it will re-encode for a DVD 9) & AC3, & if you really are *slightly* over-size, an alternative is to render your DVD to your hard drive & use Shrink or Recode.