Why is DVDAS expanding my MPEGs?

Andy C wrote on 2/17/2007, 1:01 AM
I use VMS 7 Platinum and burn shows recorded from a Digital TV card directly using DVDAS. In other words I don't need to edit the shows using the Vegas editor.

In terms of aspect ratio and pixel sizes the TV card records exactly what gets transmitted, whether that be 16:9 or 4:3. My DVDAS project is PAL Widescreen (720x576) and I get a strange phenonemon when inserting two different show formats. If the MPEG is a lesser Height x Width value than the project properties the file somehow expands to almost twice its size and therefore needs more DVD space. However, If I insert an MPEG with a matching pixel aspect ratio then it takes up no more room than if you'd copied it to the DVD. This seems crazy to me.

DVDAS displays the properties ot the two shows as follows. I've added the 'Disc Space Used' figures below each one.

File 1
Name: Star Trek 1.mpg
Type: MainConcept MPEG-2
Size: 1.29 GB (1,316,262,125 bytes)

Streams
Video: 00:54:45.760, 25.000 fps interlaced, 720x576x32, MPEG-2
Audio: 00:54:45.768, 48,000 Hz, Stereo, MPEG Layer 2

DVD Space required in DVDAS 4: 1.6GB (No size increase)


File 2
Name: Meteor Parents.mpg
Type: MainConcept MPEG-2
Size: 778.47 MB (797,155,526 bytes)

Streams
Video: 00:34:43.600, 25.000 fps interlaced, 544x576x32, MPEG-2
Audio: 00:34:43.608, 48,000 Hz, Stereo, MPEG Layer 2

DVD Space required in DVDAS 4: 2.2GB (size has almost doubled)

Now DVDAS needs 0.5GB for overheads, so we can subtract that to get the file space requirement figures of:
File 1: 1.1GB
File 2: 1.7GB

Why does the 'Disc Space Used' figure increase disproportionally for the second file with the 544x576 resolution?

I'd like to test further by setting the project to match it but unfortunately it's not an option. Does anyone have any suggestions?
Thanks,
Andy.

Comments

ScottW wrote on 2/17/2007, 3:57 PM
The second file is not a standard format for DVD's. As a result DVDAS will need to recompress the file. DVDAS frequently gets size estimates incorrect when it has to recompress something. Another possibility is that the bitrate for recompression is higher than the original bitrate, so the new file will take up more space.

--Scott
MSmart wrote on 2/17/2007, 7:06 PM
Andy, if you're not editing the files, give DVDStyler a try. I won't (most likely) reencode your video and create disc contents more quickly.

A Background

Andy C wrote on 2/18/2007, 3:10 PM
Thanks Scott and MSmart,

I tried DVDStyler and although it's very basic it does exactly what I need. I also understand DVD Lab handles these non-DVD compliant resolutiions as well, unfortunately it's pricey.
It's a shame there's no 'Switch Off DVD Compliance' in DVDAS. I'd much rather use it.

Andy.