VOB files and progressive/interlace scan

[gvm]

Is it true that a PAL VOB file on DVD contains 25 frames per second of video and that this content is in neither progressive nor interlace format?

If this is true, then I assume the DVD player converts the 25 frames into 50 fields for display via a TV, but if the DVD player is in progressive mode and connected to a progressive scan-capable device then it simply displays the 25 frames via the device.

What I am trying to get at is to understand whether the scan mode (interlace or progressive) is independent of the source DVD.

[Kika]

PAL Content on DVD can be interlaced or progressive or progressive, but encodet in interlaced mode.

then I assume the DVD player converts the 25 frames into 50 fields for display via a TV

That's true enough ;)


then it simply displays the 25 frames via the device.

This would be nice, but unfortunatly even progressive Video will be splitet into 50 Fields and deinterlaced to 25 Frames.

[Wilbert]

Good that you bring this up again, since I'm still highly confused about this issue.

As I understand you can have interlaced YV12 and progressive YV12, and mpeg2source outputs interlaced YV12. Note, it is very hard to see that it is interlaced (since it looks like progressive at first sight).

Now, if you convert it to XviD/DivX (as most people do) you run into trouble, because of missaligned chroma. Note that XviD/DivX is progressive YV12 (unless you encode to interlaced XviD).

To convert interlaced YV12 to progressive YV12 you can do the following (what no one does):

ConvertToYUY2( interlaced=true )
ConvertToYV12()

It's not possible yet without converting to YUY2.

Opinions?

[gvm]

thanks for the replies but I'm having trouble understanding. What is the answer to this question:

What I am trying to get at is to understand whether the scan mode (interlace or progressive) is independent of the source DVD.

[Kika]

PAL (and NTSC) CRT-TVs are always working with interlaced Pictures, that's a technical Fact.

If a Movie is stored as progressive Video, the Player has to split up each Frame into two Fields und send them in sequence to the TV.

[SeeMoreDigital]

Yes, this can be quite a difficult concept to get to grips with.

Even more so because many people (especially here on the forum) like watching DVD's and encodes (they've made from their DVD's) on their PC screens... And PC's and their monitors display video progressively.

If you need to see some examples of what this means I've put some on my web site. Just go to Area 51, A/V Setup Tests, Interlaced and De-Interlaced Test Files.

After downloading and opening the zip file you will see an collection of files: -

The Mpeg2 file is an Interlaced 'Reference' file.
If you view this file via a PC monitor, the numbers 1 and 2 will appear to be merged. However, if you view this file again via an CRT TV screen, you will see the the numbers: 1 and 2 flicker.

This flickering shows how the image is constructed ie: number 1 exists in it's own set of 25 fields. And number 2 exists in the other set of 25 fields.

The other files: XviD, DivX etc are encodes of the 'Reference' file and are there to show you what happens when you de-interlace an interlaced file. Again you've got to view them via a CRT TV screen and an PC screen to see the differences.

You will obviously have to have the necessary equipment carry out these tests. If you have a stand-alone DVD/Mpeg4 stand alone player, you will be able to burn all the files to a CD~R/RW.

There's also some information in 'Area 03' of my web site that may help you understand about frames, fields etc.

Cheers