Re: [OT:] Flicker Free

[Mark Rages]

On 6/8/05, Richard Prosser <[hidden email]> wrote:
> As a quick query - if movies are 24fps & TV is 25fps (50Hz) - when I
> watch a movie on TV is is "properly" converted, or do I watch a
> slightly sped up version?

Yes.

> I guess running a 24 fps movie at 25fps would not cause too much of a
> problem

You're more likely to notice the audio being 4% sharp.

> but for 60Hz systems I don't think 30fps would be acceptable
> - apart from anything else, the sound would noticably increase in
> pitch

For 60Hz systems, a system called "2:3" pulldown is used.  (I think it
is less confusing to write it as "2,3" pulldown because it is a
sequence rather than a ratio).

NTSC video is made of 60 fields per second.  So if we repeat one frame
of 24 fps film for two fields, than the next frame for three fields,
we get 2 frames of film lasting for 5 fields of video.  2/5 is the
same as 24/60.

If you think this might add some artifacts, making motion less smooth,
you're right.  But those of us in NTSC countries are pretty well used
to it.

Regards,
Mark
markrages@gmail
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[Alan B. Pearce]

>As a quick query - if movies are 24fps & TV is 25fps (50Hz) - when I
>watch a movie on TV is is "properly" converted, or do I watch a
>slightly sped up version?

Films made for TV were shot at 25fps specifically to overcome this. Other
films shot at 24fps were shown at 25fps on TV, which does give slight speed
changes (and equivalent pitch changes in sound).

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[Michael Rigby-Jones]

>-----Original Message-----
>From: [hidden email] [mailto:[hidden email]]
>Sent: 10 June 2005 08:57
>To: Microcontroller discussion list - Public.
>Subject: Re: [OT:] Flicker Free
>
>
>>As a quick query - if movies are 24fps & TV is 25fps (50Hz) - when I
>>watch a movie on TV is is "properly" converted, or do I watch a
>>slightly sped up version?
>
>Films made for TV were shot at 25fps specifically to overcome
>this. Other films shot at 24fps were shown at 25fps on TV,
>which does give slight speed changes (and equivalent pitch
>changes in sound).

Quite a few DVD productions have been using pitch shifting to eliminate this, but the pitch shifting often introduces annoying artifacts and distortion.  IMO the pitch shift isn't noticeable unless you can listen to the correct speed film next to the faster one.

Regards

Mike

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