Quantcast PAL / NTSC Conversion (Flicker) - digitalFAQ Forum
  #1  
11-28-2004, 12:01 PM
CaZeek CaZeek is offline
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Hey Mr. Smurf,
I'm not sure if you have much experience with standards conversion, but hopefully you do My current situation is as follows (I've posted in the videohelp forums as well). To play retail and non-retail PAL DVDs, I'm using a multi-region Sony DVP-NS575 DVD player (http://www.world-import.com/dvp-ns575.htm). For conversion, I'm using the CMD-1200 (http://www.world-import.com/cmd1200.htm). The DVDs are being played on an NTSC TV.

While there is no "quality" loss, I am noticing a slight "flicker" in the video when there is a lot of motion. On the videohelp forums, people are telling me that they do not witness any flicker when they convert from PAL to NTSC. From what I read online, it seemed that there is more of a flicker in PAL images naturally (due to the lower framerate), but after hearing some of the videohelp responses, I'm thinking there might be a problem with the conversion.

Note: There is no flicker in either format on my computer monitor.

To sum up, my question is basically what is the best way to convert from PAL to NTSC? To avoid the other issues involving VHS, you can speak directly about DVD conversion. My current method is running from the DVD player, to the converter, to the capture card. I've tried authoring an NTSC DVD after the conversion and playing that on the DVD player as well (still seeing flicker). Am I being too picky, is this just the way PAL video plays, or is there a solution?

Thanks a lot

Edit: Here's a link to the videohelp post
http://www.videohelp.com/forum/viewtopic.php?t=246395 - CaZeek
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  #2  
11-28-2004, 02:16 PM
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That videohelp post has lots of clueless responses. Mostly because they're answering before they heard enough of the question or don't have enough background/experience to go from. So here goes...

Converting formats has to be broken down in two categories:

1) Progressive.
2) Interaced.

Of the progressive, we have to know what the original source was. Deinterlaced footage? Or film? Deinterlaced footage was already ruined before you got it. Film is a simple software operation (well, sort of simple). You adjust speeds more than anything.

(Will round numbers for convenience.) Anyway, you have 24fps film that was released 25fps PAL. How? Well, they sped it up. Let's say the film is one million frames long, at 24fps. Well, for the PAL release, they took the same million frames, but played it at 25fps instead, and lowered the tone of the audio by 4%. It was that easy. TMPGENC and AVISYNTH can re-encode ("do not convert framerate" operation, as your just adjusting the speed). Besweet augments the audio. The "actual" number, by the way, is 23.976, not 24, and uses pulldown 3:2 to play 29.97 NTSC. Videohelp has several guides on this, which were made by xesdeeni of doom9, and I've got them as the basis for my PAL->NTSC guides that should go up Dec/Jan sometime.

Now interlaced video is a whole 'nother animal...

I hate describing the "nature" of interlace, but here's my butchered "easy" definition: Video is a series of motion images. We calculate by "frames per second", which differs depending on the format (PAL, NTSC, SECAM). Interlacing is something a TV uses, the nature of the device, and is not based on frames. It shows fields. A frame is essentially TWO fields together at the same time. A field is just a portion of the image, and all frames are tied together because of this. The fields from one frame may be needed by fields in the next frame to actually form a coherent image.

Make sense? I hope so..
And if it does, can you see the problem?

The best analogy I can give is Photoshop. Open a decent sized image and use the magnifying glass. 25%, 50%, 75% and 100% look great. But what about 33% or 66%? Not so great. Same scenario. Your math is not an exercise in perfect division. Because of this, it will never be perfect visual quality, but we work to keep the damage minimal.

A hardware device dedicated to this process was a smart move. You're going to need it. Software just cannot compete with certain aspects of video, and this is one of them.

At this point, you're seeing what's expected. Interlace interruptions (whether DE-interlaced, or converted interlace) shows errors at times when interlace is most exaggerated: fast motion.

Software DVD players mask this because they incorporate varying degrees of advanced/adaptive de-interlace filters (usually speed-up methods like bob/weave). The tv has no such filters.

And people wonder why I bought a Cyberhome 300. Pop in the PAL DVD, and enjoy the disc. Forget all that work. VHS is the only time work is involved, not much choice there.

If it's REALLY bad, you can always de-interlace. That's not going to be a great option, but it just depends on what you consider to look best. You're seeking the lesser of evils, not perfection. I've tried pretty much every method I could find or come up with on my own.

Most people you run into online, especially places where newbies and non-serious hobbyists hang out, are just accepting of bad quality. I've had jerky, jittery, blocky, twangy VCDs shown to me by people that announce "great quality, huh?" with a seriousness I find disturbing. So be prepared, on this topic, to find people that just drop PAL into encoders, load a template, and hit the "go" button, and walk away 100% happy with motion errors, ghosting, etc. Word of warning, so you don't end up too confused on this topic. We've had the talk about your seeking ultimate high quality, so I always keep this in mind when responding to your questions. I'm going to give you the answer as straight, loaded and honest as possible.

Even the NTSC-50 playback on NTSC DVD players that are PAL-cooperative have motion errors from time to time on interlaced materials.

I believe this is different than "flicker" too. Flicker is a problem of data being too small or in bad places on screen, causing it to jump around trying to find the best place to display. 720x480 video inherently does this quite often, something I noticed years ago, as the resolution is not really supported by tv sets.


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  #3  
11-28-2004, 03:02 PM
CaZeek CaZeek is offline
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First of all, let me express how glad I am that I joined the forum. I'm finally seeing the whole picture with some of these issues I've been dealing with. Thanks a lot

I'm assuming that all retail DVDs would be interlaced. If this is the case, then I'm pretty sure all of the PAL DVDs I have are indeed interlaced. On a side note, is there a program that can check whether the source is top field or bottom field first?

Secondly, this is more of an "understanding" type question, and it might be pretty simple and stupid, but just to make sure, as understanding usually leads to practical application. The reason I couldn't just "speed up" the PAL frames to play 29.97 fps and then just lower the audio tone is that the video would play too fast (5/25 = 20% faster), where as 23.976fps to 25fps is not really noticeable, correct?

What do professional studios do to release their DVDs in different format? In other words, what are they doing that I am not? Is it just the $25,000 equipment that I am not using? If that's the case, then is there "any" way to improve my result via reasonably priced hardware or software? The company I bought the converter from claimed that they use it for their own conversion services..

Lastly, concerning PAL-playble NTSC DVD players (like the Cyberhome 300).. How is the "NTSC-50" signal different than the standard "NTSC" signal, and why would it play better than a PAL source converted to true NTSC? I'm assuming 50 is a reference to the fields per second, but that's purely an assumption.

Feel free to direct me to another website article if any of my questions have already been answered. I do appreciate your giving me the "straight, loaded, and honest" answers. If I were looking to settle like the people you described, I think I'd be talking to the wrong person
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11-28-2004, 03:43 PM
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Most commercial DVDs, movies at least, are progressive. TV shows can range. I think my Smallville and Stargate are progressive, for example, but my Slayers cartoons are interlaced. So your assumption may be true, may be false, must test files. Simply looking at the VOBs in Womble MPEG-VCR is generally fine (zip through file, look for interlacing). It's what I do.

GSPOT 2.51 beta 02 (or higher) will open the VOB and tell you the MPEG properties. It has I/L (TFF, BFF), 3:2 and PROG for interlace info. 3:2 is PROG too, with pulldown. This is usually very precise. I still like Womble to see with my own eyes.

Homemade stuff depends on the person, interlaced if they were smart, deinterlaced if they weren't, or if by some miracle true progressive if they had true progressive source.

24 and 25 are almost inconsequential. You'll notice PAL releases are generally 2-4 minutes different in length from the USA release, and this is why. You lose a frame per second, a second per minute, two minutes per hour, etc. Or something like that. Official fim releases are 23.976 too, with 3:2 pulldown. Open TMPGENC, look at the MPEG-2 encode settings, you'll see interlaced, non-interlaced, 3:2 pulldown. It's a display/playback flag. DVD players were made to do this.

Pros use progressive material. They make NTSC and PAL and SECAM separately. They do not convert formats. They make formats from film. In odd cases where film was not the source, they do what we do when converting: suffer the consequences and deal with it. But yes, a $25K+ video toy makes it quite a bit less than our sub-$500 equipment.

I'm sure you've put a PAL tape into a NTSC VCR. Who hasn't? It loses v-hold, goes B&W with some chroma flickers, and has other oddities. Well, PAL, NTSC, etc., are more than just framerates. They have different color systems. Power requirements, etc. Frame rate is the least of your concern. Some of this is a bit fuzzy to me too, you get into engineer and tech speak (I hate gobbly-gook words) but I do know that DVD players don't "convert" the signal. Not fully, at least. It cannot change the framerate, so you still get 25fps, and thus see artifacts from time to time. The tv can handle that. Over there, NTSC plays as PAL-60. Inverse situation. PAL is too big too, larger vertical than NTSC. Many players botch this up. Cyberhome and LiteOn are a few of the ones that don't, they resize the vertical axis correctly. Some of the forgiving recorders don't care about incorrect frame rates and seemingly grab at 30fps anyway. Go figure. VCRs probably could have acted this way too, but just never did. PAL VCRs have always been able to play NTSC (as PAL-60), we got the shaft.

The Cyberhome won't really make it any better, but it probably won't make it much worse either. It's lazy and quick if you just want to watch it. I could probably make some decent money converting people's PAL home movies to NTSC, but I just assume talk them out of it. A quick $30 for a player I feel is the best solution. To date, all but one of them have conceeded (and the NTSC conversion turned out fine, but not 100% perfect being from interlaced source PAL DV).


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I make a terrible teacher. Teachers have to drill information into somebody (and the pupil is often ignorant or stubborn, or both!). I just share what I know and those that want to learn will hopefully gain some insight from my knowledge/experience. It's the old "those that help themselves" cliche in action.

Just be glad you're not forced to watch some of the videos some people make. Jerking video can actually make you noxious! I'm actually working on a joke of sorts, a single DVD with 29 hours of video. What's sad is it still looks better than some discs I've seen people make.




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  #5  
11-28-2004, 04:07 PM
CaZeek CaZeek is offline
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Ok, I think I'm understanding most of this now. So as far as my retail sources, I'll check if they are progressive, and if so, I'll use the progressive software method. So if there were a "Do interlaced PAL -> NTSC conversion the DigitalFAQ way" guide, it would pretty much be my process (with the exception of perhaps going through a proc amp and directly into a DVD Recorder)?

One more question though.. why can't I just slow down the 25fps PAL interlaced DVD to play at 23.97fps and raise the audio tone? Isn't 23.97 a valid NTSC DVD framerate?

Thanks again
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  #6  
11-28-2004, 04:15 PM
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Yes, that'd be my method. All hardware, cross your fingers.
If I got desperate, I'd just live with whatever an adaptive deinterlace can salvage, should the hardware method make a mess (rare).

Interlace cannot be 23.976.
It must be progressive, and it must have the 3:2 flag.


Fun, huh?

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  #7  
11-29-2004, 09:45 AM
CaZeek CaZeek is offline
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Thanks for all of the replies. I really appreciate the info.

PS I noticed that there's a lot less of the "jumpiness" in most of the episodes than there is in the one or two I was particularly botherd by. I'm thinking I had something set wrong when I capped those (maybe had the output to a different PAL format than the cap card was set to receive?). I'll give it another run through.
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  #8  
11-29-2004, 10:28 AM
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Could be. Depends on your capture software. I forget precisely what you're using. ATI MMC?

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11-29-2004, 10:37 AM
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Yep.. I think the newest version available on the ATI website. I don't actually have access to my equipment or that computer now. As you know, I've been jumping around recently, and I'm now back in D.C. for the next few days, so won't be able to try anything out until I get back to NJ... possibly later this week.
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  #10  
12-03-2004, 07:53 AM
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Just to update, I tried recapping the episodes, and the "problem" episodes turned out much better. There's still the slight jitter now and then, but I'm much happier with the results. As far as my retail stuff, most of it has macrovision on it, so it was tough to tell interlace in Womble / VDub (although I could detect what I thought was interlace sometimes). GSpot 2.51 worked out great.. big improvement over the older version.
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  #11  
12-03-2004, 08:14 AM
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For those with MV, rip to the HD (a single VOB will do), and test from there with GSPOT.

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