[adyc]

I have some questions regarding deinterlace process of dvd player.


Most of dvds (not all, I have some dvd which are interlaced encoded) are encoded in progressive format. There is no need for deinterlacing.


So what does progressive dvd players do with these progressive encoded dvds? Theoretically, there is no need to deinterlaced these signals

 

[brianh]

Hello adyc,


Contrary to popular belief, DVD's are essentially ALL interlaced! It is a requirement of the output to provide 60 interlaced fields (30 images) per second for NTSC compatibility. On DVD's that have a 24 fps film source (most), if it has been properly "flagged" as to which fields are replications of others, and which pairs of fields go together to form the original full image frame (from the 24 fps source), then progressive players can grab this information and provide a progressive output to TV's capable of 480p.


I have heard of some progressively encoded DVD's, but I'm not sure of the details, and if normal players could handle them, etc.


Any knowledgable feedback/comments?


Brian

 

[adyc]

Thanks for the info. Now the question is that the progressive signal output by progressive dvd players are 30fps or 24fps?


As you said, there are flags to help dvd players to deliever the interlaced pictures. However, xmpeg does not rely on these flags, they read the progressive signals directly from dvds (try the xmpeg program to determine whether your dvds are progressive encoded or interlaced encoded). Why can't these progressive dvd players read the progressive signals directly from dvds just like xmpeg when it converts to divx? It saves all the troubles of deinterlacing properly.

 

[sspears]

480p players output 60 frames per second.

480i players output 60 fields per second.

Quote:

Why can't these progressive dvd players read the progressive signals directly from dvds just like xmpeg when it converts to divx?

The inferior progressive scan players do and that is why they don't do as well as those that read the cadence.

 

[dmunsil]

Quote:

Originally posted by adyc Thanks for the info. Now the question is that the progressive signal output by progressive dvd players are 30fps or 24fps?

It's 60 fps

Quote:

As you said, there are flags to help dvd players to deliever the interlaced pictures. However, xmpeg does not rely on these flags, they read the progressive signals directly from dvds (try the xmpeg program to determine whether your dvds are progressive encoded or interlaced encoded). Why can't these progressive dvd players read the progressive signals directly from dvds just like xmpeg when it converts to divx? It saves all the troubles of deinterlacing properly.

There are lots of DVD players that do exactly what you're describing. The problem is they don't work very well when the flags aren't perfect, and the flags aren't perfect a surprising amount of the time. xmpeg has the same problem and does, in fact, rely on the flags.


For more, you can read the article I wrote on this very subject:

Progressive article


Don

 

[MDRiggs]

Quote:

Originally posted by adyc I have some questions regarding deinterlace process of dvd player. Most of dvds (not all, I have some dvd which are interlaced encoded) are encoded in progressive format. There is no need for deinterlacing. So what does progressive dvd players do with these progressive encoded dvds? Theoretically, there is no need to deinterlaced these signals

Most DVDs actually are encoded with interlaced signals (more efficient compression), but since the MPEG decoders produce interlaced output even if the signal on the disc is progressive, it doesn't much matter. The decoder takes what's on the disc and converts it to 30-fps interlaced video. In players with progressive output capability, there is a deinterlacing circuit that takes the output from the MPEG decoder and works it over appropriately. A good deinterlacer can do a near-perfect job of reconstructing film frames, so it's not a big deal provided you make sure you get a player with a good deinterlacer.

 

[dr1394]

When folks say that DVD's are "progressive", it's

not that far from the truth. A DVD that's been

encoded from film source with inverse telecine

is a sequence of progressive MPEG frames at 23.976

frames per second. The repeat_first_field and

top_field_first flags are used to convert from

the 23.976 MPEG progressive frame rate to the 29.97

interlaced display frame rate.


So progressive DVD players are actually destroying

the nice progressive MPEG frames by converting to

the display rate and then de-interlacing back to

progressive. It's a bit goofy, but necessary to deal

with DVD's that are encoded as video (either 29.97 fps

source or film source without inverse telecine).


Ron

 

[adyc]

Quote:

Originally posted by dmunsil It's 60 fps There are lots of DVD players that do exactly what you're describing. The problem is they don't work very well when the flags aren't perfect, and the flags aren't perfect a surprising amount of the time. xmpeg has the same problem and does, in fact, rely on the flags. For more, you can read the article I wrote on this very subject: Progressive article Don

Thanks for your excellent article. It certainly clears up a lot of misconception I have. Thanks again.