25fps to 50fps

[stavas]

Hi all,

I recently bought myself a Panasonic TH-PX80 plasma, and tried out playing some HD material on it (720p and 1080p). I had heard that the picture could be a bit jerky when there was big sweeping horisontal motions in the movie. So i started up a National Geographic HD clip, and to my delight the picture was super smooth.

But, when i tried other HD material, like Planet Eart, the picture got really jerky, just like people on the forums had said. Finally i figured out why there was such a big difference, the Nat Geo clip was at 50fps, and the other HD clips was at 24fps.

I guess that the 50fps probably just was a interlaced 25fps, not a true 50fps. What do you think?
Now, to my question that justifies me posting in this forum : If this is the case, is there maybe any way to convert 24fps clips to 50fps (if it's just interlaced)?

// Regards, stavas

[jagabo]

I'm guessing you're using a computer hooked up to your HDTV via HDMI. What resolution are you using? Is the refresh rate set to 50 fps? Interlaced or progressive? What resolution are your source clips? MediaInfo or GSpot should be able to tell you the video file properties. If your HDTV accepts 1080p at 50 Hz use that. If not, try 1080i at 25/50 Hz.

"Really jerky?" -- I think your computer is just having problems decoding the 24 fps video. Normally a 24 fps video playing back at 50 fps will display each frame of the source twice, except every half second a frame will be displayed 3 times. So twice a second you should see a small jerk.

[jman98]

Who knows? Note that your video clips were converted by others and we have no way to know what they did. Poor resizing filters could lead to what you saw. And 50 fps can be all progressive. In fact if it's 720 it will be 720p. I've never seen 720i video. BluRay doesn't support it, but theoretically you could make it. Why you would make it is a good question.

Yes, 24 fps can be converted to 50 fps via AviSynth, but since your problem is most likely that the person making the video available screwed it up, such a conversion is extremely unlikely to fix any of the problems.

[MysticE]

Hi all,

I recently bought myself a Panasonic TH-PX80 plasma, and tried out playing some HD material on it (720p and 1080p). I had heard that the picture could be a bit jerky when there was big sweeping horisontal motions in the movie. So i started up a National Geographic HD clip, and to my delight the picture was super smooth.

But, when i tried other HD material, like Planet Eart, the picture got really jerky, just like people on the forums had said. Finally i figured out why there was such a big difference, the Nat Geo clip was at 50fps, and the other HD clips was at 24fps.

I guess that the 50fps probably just was a interlaced 25fps, not a true 50fps. What do you think?
Now, to my question that justifies me posting in this forum : If this is the case, is there maybe any way to convert 24fps clips to 50fps (if it's just interlaced)?

// Regards, stavas

Here in the States, Panasonic plasmas convert 24 fps to 60 fps by using 3:2 pulldown hence the judder inherent in the process. It's the same thng that Blu-ray players will do if you select 1080p over 1080p/24.

[edDV]

24p (film) can be jerky in pan unless carefully controled. This ideally takes motorized camera mounts. Planet Earth was shot in 24p (some film but mostly Sony HDCAM). For PAL, 24p is sped to 25 fps and interlaced for broadcast in 576i or 1080i.

The National Geographic show may have been shot in either 1080i or 720p@59.94 or 50 fps. In both cases motion update would be more than twice 24p so pans would appear smoother. Over here the National Geographic channel is carried as 720p at 59.94fps.

[stavas]

Whow.., thanks for all the serious and initiated replies in such a short time, really appreciated!

Jagabo:
I'm using a Popcorn hour A100, so it shouldn't be an settings problem.

jman98:
The jerkiness isn't that bad, it's just that I expected more from px80 together with hd. But the jerkiness is enough for me to get annoyed, and wanting to check if a conversion to 50fps would make it better. I have learnt while browsing various forums, that the jerkiness is to be expected on 1080p/24fps, since it's just that; 24 fps. The more expensive plasma tvs has different filters (for example Pannas IFC) creating extra frames. Some people think that this just makes it worse, since the picture gets more blurry when there's a lot of motion, but I find the jerkiness more annoying then the "blurriness". I have seen how the PZ85 and the Kuros (I know, I shouldn't compare the Kuros to my Panna) acts, and it was such a big difference, with the same player and the same clip.
When i bought my plasma, I didn't think that the IFC filter was worth the extra $500 (px80 --> pz85).
I'll try AviSynth just for the fun of it, but I neither think it will be a really good solution.

edDV:
Ok, so the Nat Geo is actually shot in an higher framerate. Then I suppose that trying to convert won't make that much of a difference. Thanks for the info.


Once again, thanks everyone for all the input!

// Regards, stavas

[stavas]

Who knows? Note that your video clips were converted by others and we have no way to know what they did. Poor resizing filters could lead to what you saw. And 50 fps can be all progressive. In fact if it's 720 it will be 720p. I've never seen 720i video. BluRay doesn't support it, but theoretically you could make it. Why you would make it is a good question.

Yes, 24 fps can be converted to 50 fps via AviSynth, but since your problem is most likely that the person making the video available screwed it up, such a conversion is extremely unlikely to fix any of the problems.

Ouch. Downloaded AviSynth, and realized that this wasn't so simple. Do you have any input on how I should use AviSynth, or a link with good tutorials or such.

// regards, stavas

[jagabo]

National Geographic may be broadcast as 1280x720 at 60 progressive frames per second but the source material isn't necessarily 720p60. I was just took a look one recording. It's a mix of 60 fps, 30 fps (probably 1080i deinterlaced to 30 fps, then each frame repeated twice), and 24 fps sources. I don't know what they do when converting to 50 fps.

AviSynth's SmoothFPS function can do something similar to the the new HDTVs' motion vector interpolation to generate intermediate frames.

[edDV]

National Geographic may be broadcast as 1280x720 at 60 progressive frames per second but the source material isn't necessarily 720p60. I was just took a look one recording. It's a mix of 60 fps, 30 fps (probably 1080i deinterlaced to 30 fps, then each frame repeated twice), and 24 fps sources. I don't know what they do when converting to 50 fps.

AviSynth's SmoothFPS function can do something similar to the the new HDTVs' motion vector interpolation to generate intermediate frames.

Yes, it would vary program to program. 1080i HDCAM source can be played 1080i or 720p with 59.94 motion increments. 24p source never exceeds 24 frame motion despite telecine or frame repeat.