Broadcasting Standards
There are three main video/TVbroadcasting standards in the world: NTSC (National Television System Committee), PAL (Phase Alternating Line), and SECAM (Sequential Couleur Avec Memoire). NTSC is used mainly in North- and South America, PAL is the main system in most of Europe and Asia, while SECAM is the favorite in Africa. PAL and SECAM has several substandards, and for example Thailand uses the PAL B and PAL M broadcasting standards.
The broadcasting standards differ on such things as frame rate, number of lines per frame drawn on the screen, frame size, color encoding, sound sampling rate, etc. In earlier days these differences made a vide bought in one part of the world useless in another part. However, in the digitized world of today these differences can be overcome by software.
| NTSC | PAL | SECAM | |
|---|---|---|---|
| Frames per Second | 30 | 25 | 25 |
| Lines per Frame | 525 | 625 | 625 |
| Frame Size | 720x480 | 720x576 | n/a |
Frame rate, scan line rate, and frame size of the three main video broadcasting standards. |
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Broadcasting Standard Conversion
There are three things that remain troublesome and where the ultimately perfect solution has yet to be invented: frame rate conversion, frame size conversion, and sound synchronization. When converting these things there often is a trade off between conversion speed and conversion quality.
Broadcasting Standard Conversion the Fast Way
Converting NTSC videos to PAL involves reducing the number of frames per second (fps) from 30 to 25. A fast way to do this is to remove every sixth frame. Thus the video is converted but will have a visible skip every sixth of a second. The height of each frame has to be expanded from 480 pixels to 576 pixels, which often is done either by adding 96 pixels of blank space or stretching the image vertically. Converting from PAL to NTSC is the same thing in reverse. The height of each frame is either downscaled or cropped 96 pixels, and five frames added per second. This makes the video seem to pause 1/30th second every sixth of a second.
Another cheap method is to simply adjust the frame rate. Converting from NTSC to PAL will speed up the video by 4%, which will make everyone move faster and talk faster with a higher pitch. Converting from PAL to NTSC slows down everything.
Broadcasting Standard Conversion the Good Way
The better, but more intensive, way of converting between the broadcasting standards is to "blend" the frames to match the new frame rate. The higher end, professional conversion software averages the information from one frame to the next by storing frames digitally in computer memory, comparing the stored frames, and adjusting each frame to produce natural motion. The better software can detect and differentiate between moving and stationary objects to further improve motion quality. The frame size still has to be cropped or stretched respectively, but the result will be much more pleasing to the eye.
These techniques are computationally very demanding processes. On slow systems, it may take 15-20 hours to convert just one hour of movie. Satiariyan only do broadcasting standard conversion the professional way and on our systems, it usually takes 3-4 hours to convert one hour of movie.
