Posted by Jukka Aho on 12/12/06 03:21

Citizen Bob wrote:

>> Just saying it was "a standard DVD" does not indicate whether it
>> contains this type of [truly interlaced] material or not.

> I meant a commercial DVD or a copy of one.

Commercial DVDs may contain real, interlaced video too. Depends on where
and how the material on the DVD originated.

- If it's a DVD version of a movie (originally shot on film) you're
safe - except for the extras, which might be (partly) real video.

- TV shows are more at suspect. Some of them are progressive and
originally shot on film, some others have been shot with a video camera.

- Concert DVDs from popular artists and music videos can contain either
type of material.

But these days there are also video cameras which can be set to either
progressive or interlaced mode, or the material could have been
deinterlaced in post, so the type of the camera does not always
necessarily indicate the type of the material.

The bottom line is: unless you shot the material yourself, or unless it
is a Hollywood flick (which is pretty much guaranteed to be progressive,
albeit usually with a 3:2 pulldown on NTSC DVDs), you don't know the
type of the material.

Fortunately, if you're unsure, it's easy to check the type of the
material with a simple AviSynth script:

DirectShowSource("test.mpg")
SeparateFields()

(Best viewed in VirtualDub.)

Tips for analysis:

- If motion progresses in every subsequent frame, the material is
(truly) interlaced, and you'll lose half the temporal resolution (motion
smoothness) by deinterlacing and resizing. (Unless you're using special
methods, such as Gunnar Thalin's smooth deinterlacer plugin for
VirtualDub, whereby you will double the framerate, which in turn allows
you to keep all the original information on the temporal axis, instead
of throwing half of it away.)

- If it motion advances only in every second frame, it's progressive
material. The adjacent fields that match each other can be combined into
frames with no fuss or ill effects.

- If motion advances with a 3:2 pattern, it's a 24(*1000/1001) fps
telecined movie clip (i.e. progressive material, once you carry out the
inverse telecine operation.)

--
znark

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