Converting between NTSC and PAL video

by Andrew Alexander
Published on Feb 13, 2004 12:00 AM



Television systems across the world are different. The two most popular formats are NTSC, used in North America and beyond (National Television System Committee) and PAL, used in Europe (Phase Alternating Line). Since you record a signal on a camcorder that ultimately is supposed to be watched on a television, camcorder manufacturers make different models of the same basic unit to support these different television formats. Not surprisingly, video shot on one system won't work on another system. This doesn't help when you want to show video of the kids to your family overseas.

(For more information on video standards, check out the National Center for Supercomputing Applications World Wide Television Guide.)

There are ways around this problem. Before I get to that however, I want to discuss a bit about how the formats are different, and the same.

As far as camcorders are concerned, NTSC video is characterized by a frame size of 720x480, and produces images at a rate of around 30 frames per second. PAL video is slightly different in that there is a bit more image quality - the frame size is 720x576 - but it only produces 25 frames per second.

When a miniDV camcorder sends data out from its DV port (known similarly as firewire, i.Link and IEEE1394), it doesn't matter what format the video was shot in. As far as the computer is concerned, it's just a bunch of ones and zeroes. In fact, if you do some basic math, you see that NTSC and PAL have a common bandwidth that makes data transmission work:

NTSC: 720 x 480 x 30 = 10,368,000
PAL: 720 x 576 x 25 = 10,368,000

So, regardless of whether it's NTSC or PAL data, the computer knows what to expect. And when you capture it to the computer, most editing programs will be able to work with the video regardless of the format. However, that's where the fun begins.

Conversion: the quick and dirty way
Editing programs allow you to change the frame size easily enough, and there are also options for changing the frame rate. The frame size is easy, but the way most programs change the frame rate is to just add or remove a proportionate number of frames to make up the difference. For example, to change from 30 frames per second to 25 frames per second, you have to remove 5 frames every second. The simple way of doing this is to just take out every sixth frame (30/5=6). But what this actually ends up doing is giving your video a 'skip' every sixth of a second (which in practice, is pretty disorienting). If you can live with that, then converting from NTSC to PAL is as simple as that. Of course you also have to expand your frame size from 480 pixels to 576 pixels of height, either by adding 96 pixels of blank space or stretching your image by 20% vertically. Either way, you're going to have to recompress each frame of your video, so you may be letting it run overnight.

Converting from PAL to NTSC is the same thing only in reverse. You have to compress your image by 20% vertically, or crop 96 pixels; and, you have to add five frames to every second. This will make your video seem to 'pause' every sixth of a second, for 1/30th of a second.

Alternately, you could just change the frame rate of the actual video from standard to the other. For example, changing from NTSC to PAL, you would adjust the frame rate to 25 fps. This has the operative effect of speeding up the video by 4%, which is going to make everyone talk a little faster. The easiest way would be to use a program like VirtualDub, but unfortunately it doesn't support miniDV video, so you'll have to do some digging on your own there.

Conversion: the more intensive (and possibly expensive) way
The better way of converting from NTSC to PAL is to use a program like After Effects to 'blend' frames to match the new frame rate. This is a very computationally expensive process and is definitely an overnight thing. You still have to crop or stretch the frame size to fit, but the results will be much more pleasing to the eye. There are even plug-ins which are designed to specifically address this problem.

If you're interested enough in standards conversion to lay down $145 on a piece of software, a company called DVFilm offers a product called Atlantis which apparently does this conversion with ease. Though I can't speak to the results, the testimonials are pretty convincing. For more information check out DVFilm Atlantis.

The last and most robust solution for NTSC-PAL conversion is a multi-format VCR. These VCRs will convert a signal between two standards, allowing you to play PAL on one and record NTSC on the other (or vice versa). Again, these models can be quite expensive, so for a one-time-only experience it may be worth your while just to track down a store which will do it for you.