You are here: Re: Is NTSC **REALLY** necessary for USA DVD sales? « Video Production « DVD MP3 AVI MP4 players codecs conversion help
Re: Is NTSC **REALLY** necessary for USA DVD sales?

Posted by Jukka Aho on 11/14/06 02:55

Veggie Dave wrote:

>> By deinterlacing 50 fields-per-second material to 25
>> frames-per-second, then slowing down to ~24 (23.976) fps, you will
>> lose half of the original temporal resolution. (I.e., motion will be
>> twice as juddery as in the original - watch out for those fast pans
>> and zooms! - and it will also get the 3:2 judder from the 3:2
>> pulldown in the NTSC DVD player.)

> I've actually found that there's a lot less judder doing it this way
> than to normal interlaced 29fps, particularly with high speed images
> (which is what 90% of what I shoot and edit is). The interlaced PAL is
> auto-deinterlaced in the conversion process.

I'm not arguing that the motion quality would be worse than with a
straight conversion. It may very well be better. But I'm arguing that...

1) ...it requires deinterlacing, which will throw half of the original
temporal resolution (smoothness of motion) in 50 Hz interlaced PAL
pictures out of the window (of course, that doesn't matter if the
material wasn't interlaced to begin with),

2) that not all video processing tools will automatically deinterlace
when doing this kind of conversion (so you will have to know the
internal behavior of the tools you're using for this type of
conversion),

3) that if no frames are dropped in the 25 fps -> 23.976 (24*1000/1001)
fps conversion (in other words, video is simply slowed down), this type
of conversion will require time-stretching the audio,

4) that if frames _are_ dropped in the 25 fps -> 23.976 (24*1000/1001)
fps conversion, well, then I'm not sure what is the point of this
exercise, since dropping frames introduces motion judder, and

5) that some motion judder will be added, anyway, due to the 3:2
pulldown done in the viewer's DVD player (but NTSC viewers are used to
that, so it may not be too objectionable)

> But if your only option is a software conversion exported from an NLE
> then it's a better solution than to 29fps.
>
> It's not the perfect way to do it by any means, but if you don't have
> access to, or can't afford to do it the way TV broadcasters/program
> distributors do it, then it can be an acceptable solution - certainly
> in the context of the original question, anyway.

I agree with that, even though I would probably want to keep it
fields-based even in the 25 fps -> 29.97 (30*1000/1001) fps case (better
granularity). Again, assuming interlaced source material.

> I'm very interested in this Avisynth that you recommend, but sadly
> their site's down at the moment.

Their provider had a HDD failure of some sort and they're now in the
process of recovering from that. Fortunately, an archived copy of the
former web site is available at <http://www.archive.org/>:

<http://web.archive.org/web/20060531222927/http://www.avisynth.org/>

See

<http://web.archive.org/web/20060522030557/www.avisynth.org/YourFirst
Script>

and

<http://web.archive.org/web/20060525185608/www.avisynth.org/FiltersBy
Category>

The copy linked above is the latest. For some reason, however,
archive.org often does not include all pages in every archived copy. If
you find that some pages in the archived copy are missing, try an
earlier copy of the same site from this page:

<http://web.archive.org/web/*/http://www.avisynth.org/>

* * *

Some Avisynth script examples for standards conversion can be found here
(near the bottom of the page):

<http://www.geocities.com/xesdeeni2001/StandardsConversion/>

Also at the beginning of this thread, in a scrollable subframe:

<http://forum.doom9.org/showthread.php?s=&threadid=35387>

The above examples use the ConvertFPS filter, which is for
frame-blending. It used to be a separate plugin filter, but has later
been incorporated to Avisynth as a built-in filter:

<http://members.cox.net/hansenjo1/ConvertFPS.html>
<http://www.google.com/search?q=convertfps>
<http://www.guthspot.se/video/AVSPorts/SmoothDeinterlacer/>

As you can see from the above script examples, they tend to work their
magic on the field level, not on the frame level.

--
znark

 

Navigation:

[Reply to this message]


Удаленная работа для программистов  •  Как заработать на Google AdSense  •  статьи на английском  •  England, UK  •  PHP MySQL CMS Apache Oscommerce  •  Online Business Knowledge Base  •  IT news, forums, messages
Home  •  Search  •  Site Map  •  Set as Homepage  •  Add to Favourites
Разработано в студии "Webous"