Frame rate


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Frame rate

  1. 1. Frame Rate (fps) : All of the movies, TV shows or video games you see are made up of still images played in a fast succession the illusion of a moving image, similar to a flip-book. Each image is called a frame and the rate is the speed in which they are played, the higher the frame rate the smoother moving objects will appear but also increase the file size drastically. <br />The human eye can notice hangs/delays on clips running less than 30 frames per second, anything above this is essentially overkill but can make sharp, fast movements more fluid. However, since the human eye doesn’t see in frames, 24fps/25/29.97 etc still look fluid to us and we would have to look very closely to notice, and would only show up on very fast movements – as an example, Tennis is always awkward to watch on TV because of this problem.<br />Below, is a list of commonly used frame rates, what they are used for and a brief description.<br />FPSSeen whereDescription24PAL; Films & HD VideoThis is the universal standard film frame rate and is almost always shown in Cinema’s around the world.23.98NTSC; Films & HD VideoThis is essentially 24 FPS running at 99.99% of the speed to be compatible with the NTSC drop frame, for everywhere where NTSC is, this is the big thing - expect this to be running when watching films.25PAL; HD Video / TVThis is the rate that all PAL TV will run at and is the European video standard. Some films also run at this frame but typically prefer 24.30PAL / NTSC; (Black & White) Video & PC’s.Before colour was added to NTSC video signals, this was the standard frame rate for video to be broadcast in but is almost never used in today’s world. Typically, when people say 30FPS they are just rounding off 29.97 and can lead to confusion.29.97NTSC; HDTV / TVWhen colour was introduced to TV’s in 1953 this became the NTSC Video Signal standard for TV broadcasting and is a very common video frame rate. 50PAL; Interlaced TV.This is the interlaced field rate for PAL TV Broadcasting and runs at twice the frame rate. Most High-Definition camera’s can record at this frame rate. 60HD Video, PC’s, Gaming.Since the majority of displays run at 60Hz this frame rate gives the highest level of smoothness capable, but due to the high file size this is impractical to broadcast. However, for gaming where smoothness is critical it is desired to have a PC Capable of staying stable at 60FPS or above in all scenarios. (Pre-Vertical Refresh)59.94NTSC HD Video, PC’s, Gaming.NTSC Compatible version of the above.<br />Compression:<br />Raw footage has a massive file size, too large to be broadcast in real-time or effectively shared, to combat this files are compressed which reduces the file size drastically, but it does the same to the image and sound quality, too.<br />The more you compress anything, the worse the quality will get and many user-generated videos that plague YouTube suffer from far too much compression resulting in pixilated footage which was shot in High-Definition.<br />The best way to compress files without impacting quality is to remove things that humans cannot perceive – As an example, there are millions of colours out there, but humans can only detect 1024 different shades, so why keep all of them and not throw some out? This is known as psychovisual video compression and is used when compressing to WMV’s/MPEG’s/Others this does reduce some quality, but not to a stretch which is noticeable. The other technique that doesn’t discard quality is Lossless compression, which doesn’t compress the file size by that much but does not remove any quality from the video whatsoever.<br />Lossy compression has the most visual impact but discards by far and away the most data. This can change anything from the resolution, to the frame rate, audio bit rates etc. These should only ever be used as a last resort to reducing file size, but are often the only means of achieving something realistic.<br />Common Video File Types:<br />.AVI - Audio Video Interleave File (Lossless)<br />.MOV – Apple Quick Time Movie (Lossless/Lossy)<br />.MPG – MPEG Video File (Lossless/Lossy)<br />.VOB – DVD Video Object File (Lossy)<br />.WMV – Windows Media Video File (Lossy)<br />.SWF – Shockwave Flash Movie (Lossy)<br />.FLV – Flash Video File (Lossy)<br />Aspect Ratio:<br />2.35:1 (2.39:1) This offers an extremely wide viewing area and is often used for cinema, this aspect ratio is often far too wide for home viewing, which is why, when you often watch movies back at home there will be letterboxing, black borders which cut off the top and bottom to keep the original aspect ratio. This is known as 2.35:1, although the actual resolution is 2.39:1 because it is a relatively new convention.<br />1.85:1 (16:10) <br />American Theatrical Standard – Slightly wider than the much more commonly used 1.78.1 (16:9). Letterboxed.<br />1.78:1 (16:9)<br />Standard for HDTV/Widescreen TV’s. Letterboxed.<br />1.33:1 (4.3)<br />Standard television aspect ratio. Letterboxed.<br />1.33:1 (Anamorphic Widescreen)<br />This stretches the video so that the letterboxing is removed, people only generally do this on smaller TV sets so that the image is viewable from a reasonable difference although distorted. Basically, a last resort.<br />