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PAL/NTSC converter question

post #1 of 12
5/26/12 at 4:03am
Thread Starter 
I have been looking around at PAL/NTSC converters and thought of something that I would normally think would be an issue but somehow from what I am reading is not an issue with some of the converters.

Some of the converters out there do not have audio connections. The manufacturers/sellers say that the conversion is done in real time and there are no audio delays or lip sync issues. There seems to be enough positive reviews out there that indicate this is not a issue, but I can not understand how this can be possible if the audio leads bypass the PAL to NTSC or NTSC to PAL converter.

Because of the 30 vs 25 frame rate differences from what I have seen NTSC DVD's run approximately 4 minutes longer than the identical movie on a PAL DVD. I have never really paid much attention to VHS run times but I guess that would be the same too

If you run a PAL movie though a converter and convert it to NTSC wont it slow it down by about 4 minutes (because of the length of the movie you do not notice the speed difference with the naked eye) and make it the length it would have been if you could buy the same movie but in NTSC, but because the audio runs straight from player to TV or DVD recorder wont the audio be too fast by about 4 minutes and when the audio is finished there is still another 4 minutes of video coming through the converter?

This is totally puzzling to me. I can not see how its possible to have the audio match the video when its not processed at all.
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post #2 of 12
5/27/12 at 12:02pm
You are correct in that there is a time difference. But it is generally considered insignificant. The result is a very slight pitch change. But even in the professional mastering business the devices used to correct this pitch change were often not used because the difference is so small.

Also note that in Europe, they simply ran film shown on TV at 25fps rather than deal with the 24/25hz difference. The error was so slight most people never noticed it.
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post #3 of 12
5/28/12 at 12:28am
Thread Starter 
Thanks but that did not really answer my question. A typical NTSC movie is 90 mins long. The same movie realeased in PAL region will be about 86 mins long. Some people not in the know, look up the film on IMDB or wikapedia etc and see the run time as 90mins and then panic because their PAL DVD is 86mins and they think its cut which it is not. They are the same.

So what i am saying is if you run that PAL movie through a converter that has no audio inputs (audio leads run direct from player to recorder) and then the video lead runs through the converter. The converter converts PAL to NTSC. Because the audio is not processed it plays at normal PAL speed. At 86mins the audio stops but because of the conversion to NTSC, the video keeps on playing for another 4 mins till 90 mins.
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post #4 of 12
5/28/12 at 4:50am
I don't believe the converters speed up the video frame rate from 25fsp to 29.97fps. What happens when converting PAL to NTSC is a pull down conversion. Certain frames are duplicated every second - to make 30 frames out of 25 frames. That's why you get a very jittery motion with cheap converters. So the length of program stays the same because certain frames are duplicated every second. The audio should stay in sync thru out the video

I watch on the fly PAL to NTSC converted television all the time. Watched the Formula One race, which certainly must be shot with PAL cameras. Watch BBC world which must be live PAL cameras yet I'm watching it on my NTSC TV Live and the same length as in PAL countries.

Yeah, its more frames per second or "more frames each second for the same length of program time, no? The frames just go by faster in the same amount of allocated time?

Look up PAL to NTSC pull down and you should get a better explanation then I can give.
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post #5 of 12
5/29/12 at 9:41pm
Quote:
Originally Posted by Cyclone82 View Post


So what i am saying is if you run that PAL movie through a converter that has no audio inputs (audio leads run direct from player to recorder) and then the video lead runs through the converter. The converter converts PAL to NTSC. Because the audio is not processed it plays at normal PAL speed. At 86mins the audio stops but because of the conversion to NTSC, the video keeps on playing for another 4 mins till 90 mins.

They will be in sync, or at least very close. Think about it - you are doing a real-time transfer. The audio and video are being read at the same time. To wind up 4 minutes apart, the player would have to be playing back the audio and video separately, but it can't. It plays them back at the same time. There is no way a DVD player, or a tape machine, can simultaneously read the audio and video of a title, four minutes apart. However, there will be a very slight pitch change in the audio.
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post #6 of 12
5/30/12 at 1:44am
Quote:
Originally Posted by kjbawc View Post

However, there will be a very slight pitch change in the audio.

If you re-read OP’s post Cyclone wrote:
Quote:
Originally Posted by Cyclone82 View Post

Some of the converters out there do not have audio connections.

There is no audio processing done so it would be impossible for the audio pitch to change. The converter is processing the video only. To stay in sync for the duration of the program the only conclusion can be that the program-time does not change at all. A two-hour eight second movie must remain two hours eight seconds long. So the only possibility I can think of is that the video processor is “on the fly” making 29.97 frames out of the original 25 frames each second and every second. On the fly motion interpolation like you see with live Olympic coverage with fairly accurate timing in NTSC and PAL.

My two worries with a consumer real time video only converter would be:

1) Audio lagging behind the video by a few frames due to the real time processing of the video. Kind of like a TBC /Frame Synchronizer re-constructing every video frame on the fly and without audio connectors for audio delay making sure the A/V sync stays frame accurate.

2) Jittery motion due to consumer on-the fly processing - not having a chance for a second pass. Although my JVC XVN44SL DVD player does a pretty good job with on the fly PAL-NTSC. Better than my two-pass Nero but not nearly as good as a converted broadcast.
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post #7 of 12
5/30/12 at 7:07am
Quote:
Originally Posted by Cyclone82 View Post

Thanks but that did not really answer my question. A typical NTSC movie is 90 mins long. The same movie realeased in PAL region will be about 86 mins long. Some people not in the know, look up the film on IMDB or wikapedia etc and see the run time as 90mins and then panic because their PAL DVD is 86mins and they think its cut which it is not. They are the same.

So what i am saying is if you run that PAL movie through a converter that has no audio inputs (audio leads run direct from player to recorder) and then the video lead runs through the converter. The converter converts PAL to NTSC. Because the audio is not processed it plays at normal PAL speed. At 86mins the audio stops but because of the conversion to NTSC, the video keeps on playing for another 4 mins till 90 mins.

Uh, no, because the audio and the video are coming from the same source (machine). If the converter sped up or slowed down the video it couldn't do it in real time without controlling the speed of the source machine.
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post #8 of 12
6/3/12 at 5:05pm
Quote:
Originally Posted by Super Eye View Post


There is no audio processing done so it would be impossible for the audio pitch to change.

You are, of course, absolutely correct. I reflexively added that, because it is a normal effect of conversion techniques other than on-the-fly techniques. Dumb thing to do, especially given the content of the rest of my post.

Addendum: My OPPO DVD player does a fine job of converting PAL to NTSC. One of these days, I'll get one of their BluRay players, and see how well they do it.
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post #9 of 12
6/8/12 at 1:10am
Thread Starter 
Right so these consumer converters are not actually true converters then are they if the run times end up the same. I did not realise there was difference conversion types. I naturally thought that if going from PAL to NTSC that the video should come out with a 4% longer run time or what ever the exact spec is and because a lot of these by pass the audio, i just could not get my head around how it is possible for the audion and video to remain in sinc because i have the pal and ntsc versions of some DVD's and there is always about 5 mins difference. I just could not see how the manufactures could claim there is no sync issues.

So the answer is pull down/real time conversion and its not actually making a a true NTSC spec signal.

I think the quality of the conversion comes down the the $ and how much MB buffer is in the converter? I did read somewhere that only a few MB are actually needed for NTSC/PAL conversion and its just sales hype when they are claiming '64mb memory' or what ever with these converters.
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post #10 of 12
6/9/12 at 7:17am
Well I actually think that adding frames to make 29.97fps out of 25fps is better than speeding things up. It is a true NTSC signal because it’s running at the correct MHz, resolution and the correct frame rate after conversion. Can you imagine watching an Olympic event that is sped up? Yuk! Or a sped up rock concert? Yuk. I think the professional converters that the broadcasters use don’t just duplicate frames but they actually make up new frames calculating motion between the real frames. Again I watch sporting events originating in PAL and the converted to NTSC broadcasts look great. Can’t wait for the Olympics from the UK this summer.
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post #11 of 12
6/9/12 at 12:34pm
Quote:
Again I watch sporting events originating in PAL and the converted to NTSC broadcasts look great. Can’t wait for the Olympics from the UK this summer.
Let's hope they are in HD and not PAL...rolleyes.gif
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post #12 of 12
6/9/12 at 2:15pm
Quote:
Originally Posted by olyteddy View Post

Quote:
Again I watch sporting events originating in PAL and the converted to NTSC broadcasts look great. Can’t wait for the Olympics from the UK this summer.
Let's hope they are in HD and not PAL...rolleyes.gif

Whether HD or SD the PAL 50 Hz to NTSC 60 Hz conversion still applies.

In other words UK HD broadcasts, whether 1080i or 720P will still have to be converted from 50Hz (50i or 25P ) frame rates to North American 60Hz (60i or 30P )frame rates.
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