Changing frame rates

[Will20273]

Here's my problem: When I write DVD's (I use nero vision express but the same problem happens with Intervideo windvd) I find that if the frame rate is 23fps, the video pauses for a split second every couple of seconds, so when the camera is moving it looks jerky. Fortunatly it shows me the problem when I preview it in Nerovision before burning, so I think I can rule out a problem with writing speed, etc, and also it seems to work fine with all the 25fps videos I've tried. My guess is that the Nerovision program is set to encode DVDs at 25fps or similar, and so to make the audio match with video it pauses that last frame, so that 23 frames becomes 25. I read a few of the threads on the site, but couldn't see anything relevant to my particular problem. Does anyone know a program or codec I could use to correct this or even an option in the program I can change? I tried using avifrate but it seems to mess up the audio. Please can someone help me!!! Thanks :)

[manono]

Hello and welcome to the forum,

I take it you're converting a 23.976fps source (an AVI perhaps) to 25fps PAL DVD. There are a couple of right ways to do it and some incorrect ways also, which could account for your jerky playback. For example, your encoder could just be adding a duplicate frame every second to go from 24 to 25fps. That would certainly account for the slight jerkiness you see during panning scenes. You can check that by opening the m2v or mpv it gives you in VDubMod (may take a minute or so to open), and advancing a frame at a time during a motion scene to see if you can spot the dupe frames. One correct method is to speed up both the audio and video to get an insynch 25fps DVD. The other is to encode at 23.976fps, and then to run DGPulldown to set flags to output 25fps. When doing that, you can use the original unchanged audio (assuming it's AC3 already). If your encoder allows for neither of those methods, it might be time to change encoders. And there's always the chance that I've misunderstood your process.

[Manngo]

So your source is NTSC avi (23.976 fps). And you convert it to PAL DVD (25 fps). Frame number have to be increased. So one frame in every second will be duplicated, that couses the jerky effect.
You need an other method to change fps, or you can create NTSC DVD. I don't recommend the second one if you live in a PAL country.
Considering other methods, I would reccomend you to look into avisynth. I use the changefps, that blends the extra frame from the previous and the following ones and does not produce a jerky effect.
Avisynth is bundled by several dvd backup solutions such as DVD2SVCD that support forum is here, on Doom9. For me it works great for NTSC ot PAL projects.
Maybe others can recommend other solutions as well.

cheers
Manngo

[E-Male]

unless it's very old or bad PAL equipment should play NTSC

[Will20273]

Hi guys, thanks v. much for the replies, I tried using avisynth, but its way too complicated for a newbie like me! Is there a program with an option to encode at 25fps? Also I don't really understand the term "flag" which turns up a lot on this forum lol, so its tricky to understand some of the explanations. Thanks for your help, Will

[Will20273]

Quick reply to E-male, yours is a fair point, and although most DVD players do play NTSC, PS2's don't (unless they've been chipped), so I need PAL encoding.

[manono]

Hi-

Flags are software (sort of) embedded in the headers of the video stream (I think) that tell the player how to output to your display. So, by encoding for 720x576 at 23.976fps, the flagging, as created by DGPulldown set for 23.976->25, will cause the player to send an additional frame per second, but in the form of a field every half second, making the video play more smoothly when compared to encoding one duplicate frame every second, which plays much more noticeably jerky, as you've discovered. You'll also get some small bitrate savings by encoding 23.976fps as compared to encoding 25fps with the additional duplicate frame. Correct me, neuron2, if I've said anything incorrectly.

Most encoders when handling the conversion will either add a duplicate frame every second, or will add that frame by blending, as recommended by Manngo. I believe that TMPGEnc can keep it at 23.976fps, at the same time resizing to 720x576, but you have to be very familiar with its settings in order to make it do that. I don't use it, and don't know how, although I can probably find out.

Quite a few encoders can use AviSynth .avs scripts from which to encode, and it's certainly the best way to do it. If you have AviSynth already installed, you can use FitCD to give you the proper script for the conversion. It's probably going to add the line AssumeFPS(25) to the script. That will speed the playback, making it necessary to also speed up the audio. If you decide to keep it at 23.976 and use DGPulldown, then just delete that line.

[thecrock]

WILL20273,I had exactly the same problem, i use DIKO(free vers) it automatically converts video and audio to 25fps(if you configure it for pal) without the jerkiness. It will output a video_ts folder and an iso image either of which you can burn straight to dvd. The encoding takes a litttle longer than most programs i've used but the conversion quality is very good, you can set it for two pass encoding but this will take a really long time and i find the quality in one pass mode more than acceptable.

Peace.

[Will20273]

Hi, thanks manono for the Flags explanation, but I'm still having a bit of trouble working out how to use avisynth. I tried using DIKO though, which is awesome, so thanks thecrock. I just have a couple of questions about it though, which I can't find on any of the DIKO guides. Is there a way of adjusting the quality or size of the output file, and also how do I get it to create .vob files which aren't 3 minute previews of the whole thing? Thanks, Will

[thecrock]

I don't think you can manually change the size of the output files, i think diko works out the size of the file in relation to burning it to a dvd5 with a little overhead to make sure it fits. As to the vob files, you should be able to play the whole movie from start to finish with them.