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24fps progressive scan on DVD: fact or fiction?




Dear TIG members,

I am doing some independent research for an ongoing international
fanclub project involving the possible transfer of a UK vintage
television series to DVD that was recently remastered to 625 line
component D-1 tape. 

There seem to be a lot of confusion when reading about DVD mastering
among the websites/newsgroups, so I would be VERY grateful for
comments or insight from any TIG members who works with DVD
authoring/compression that would set the record straight. 

Can you please tell me if the following information compiled from
various internet sources is correct or not: 

"DVD does NOT face the same NTSC, PAL and SECAM compability problems
that Laserdiscs and other formats have been dealing with for years.
DVD is basically a worldwide standard, but there is a variety of
recording options available to the manufacturer. This has nothing to
do with the "country codes," "regional codes" and "zone locks" on the
players or discs to prevent certain discs from being played in certain
places of the world. 

The data on a DVD is stored digitally as a component video signal
using the MPEG2 compression and can be formatted for one of two
mutually incompatible television systems, The American standard (NTSC)
525/60 or (PAL/SECAM) which is 625/50. However, video from film is
usually stored at 24 frames per second, as a 24fps component
progressive scan or can be pre-formatted for one of the two interlaced
display rates. If the compression is based on a 24fps progressive
master, a PAL or NTSC DVD player will simply convert this signal to
its own format, as the 24fps signal is "universal". This is the format
used most often for film material on DVD, as it creates the best
possible picture quality when the NTSC or PAL players own MPEG2
decoder creates its own PAL or NTSC signal suited for your television
set. What is important to notice, is WHAT KIND of film transfer was
used in the first place to create the 24fps progressive signal in the
first place. When films are initially transferred to commercial video,
they are in the interlaced format, either as a 625 lines/50Hz for PAL
encoding or 525 lines/60Hz signal for NTSC encoding. These film
transfers are always made in the neutral component format, to obtain
maximum picture quality and reduce the loss of quality when dubbing
has to be made. When a 24fps progressive signal has to be created for
a DVD, a video process known as "inverse telecine" is performed. If a
525/60 master is used, normally intended for NTSC encoding, the
inverse process will remove the surplus fields inserted in the 3:2
field pull down process and restructure the interlace display to a
24fps progressive signal with a max. resolution of 720x480 pixels.
After MPEG2 encoding and compression, the MPEG2 decoder in the player
will reconvert the signal to a standard 525 line NTSC signal and
perform a 3:2 field pulldown to restore the repeated fields needed for
display on a 60Hz NTSC TV set or monitor. A PAL player playing such a
disc will convert the picture to a 625 line PAL signal, instead
speeding the frame rate 4% to 25fps, to coincide with the 50Hz cycle
of the PAL system. However, a PAL player will not be able to show more
picture detail from the same disc, unless the film was ORIGINALLY
derived and transferred from a 625 line transfer to DVD with a max.
resolution of 720x575 pixels." 

The bottom line of all of this is:

If we have D-1 component masters in 625 line at 25fps speed, can they
be converted to 24fps progressive onto DVD and used for both PAL and
NTSC players, provided the discs are coded as region 0? If so, where
is the best place to have this done? 

Best Regards, 

Ole Alstrup 




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