encoding 50fps video

bum · Post by **bum** » Fri Apr 02, 2004 8:15 pm

is their any way to encode video at twise the usual frame rate ? such as 50fps PAL for example ? i wana do this so i can slow down scene's by a decent margin without making it look chopy

dokool · Post by **dokool** » Fri Apr 02, 2004 8:51 pm

My best guess would be that you'd have to capture the video at the double-framerate, and then slow down in premiere...

-DOKool

Zarxrax · Post by **Zarxrax** » Fri Apr 02, 2004 8:55 pm

You can't get more out of it than whats there. PAL is 25 fps, you can't just "invent" frames out of thin air. Well you can technically, through some expensive software that will do interpolation of the frames. It sucks with anime though. Vegas does a sorta crappy blend thing when you slow the footage down, looks better than nothing though if you slow the footage by a lot. Your best bet though is to not slow footage that much. Do else that you can, but work around the problem.

rose4emily · Post by **rose4emily** » Sat Apr 17, 2004 8:03 pm

If you slow it down by half, it shouldn't look choppy if it didn't in the first place. The reason for this is that the amount of motion in a scene is the determing factor in how fast the frame rate has to be before you can no longer see the jump between frames, and slowing the video down by 1/2 reduces both the effective frame rate and the motion between those "frames" equally. The same concept is what allows animation studios to get away with taking two or three pictures of the same cel composite before moving it in scenes with slower motion.

Similarly, audio has to be recorded at a certain sample rate to accomidate an upper-limit frequency of half that sample rate (called the Nyquist frequency). If you are slowing the audio down by 1/2, however, you can drop the sample rate by half because you lowered all frequencies in that audio stream by half, including the uppermost limit of the waveform's frequency-domain spectrum.

There are extremes where human perception will catch on to this, as we aren't quite as linear as pure math, but it takes a lot of slowing down to get there - for instance, watching a time-lapse image of a clock's hands spinning around you can't see the second hand jumping every second, but at normal speed you can see the second hand's motion if you are looking for it. This, however, involves slowing the movement by a factor of 60-3600 times (as most time-lapse clock images I've seen make either a minute or an hour look like a second) and is still inperceptable to a casual clock-watcher.

bum · Post by **bum** » Sun Apr 18, 2004 11:18 am

you realy are the queen of necro posts

thanx for the info anyway, just that well, generaly if a topic in any of the video forums is past 1 page (or even half a page) old then the conversation has ended

SS5_Majin_Bebi · Post by **SS5_Majin_Bebi** » Sun Apr 18, 2004 6:06 pm

bum wrote:you realy are the queen of necro posts

thanx for the info anyway, just that well, generaly if a topic in any of the video forums is past 1 page (or even half a page) old then the conversation has ended

I'd hardly call 15 days a necropost. Maybe 1 month and 15 days, but not just 15 days.

CaTaClYsM · Post by **CaTaClYsM** » Sun Apr 18, 2004 6:41 pm

I would