Deinterlacing
Analog television employed this technique because it allowed for less transmission bandwidth while keeping a high frame rate for smoother and more life-like motion.
A non-interlaced (or progressive scan) signal that uses the same bandwidth only updates the display half as often and was found to create a perceived flicker or stutter.
Deinterlacing has been researched for decades and employs complex processing algorithms; however, consistent results have been very hard to achieve.
Since the interlaced signal contains the two fields of a video frame shot at two different times, it enhances motion perception to the viewer and reduces flicker by taking advantage of the persistence of vision effect.
However, interlaced signal requires a display that is natively capable of showing the individual fields in a sequential order, and only traditional CRT-based TV sets are capable of displaying interlaced signal, due to the electronic scanning and lack of apparent fixed resolution.
However, when the two fields taken at different points in time are re-combined to a full frame displayed at once, visual defects called interlace artifacts or combing occur with moving objects in the image.
A good deinterlacing algorithm should try to avoid interlacing artifacts as much as possible and not sacrifice image quality in the process, which is hard to achieve consistently.
There are several techniques available that extrapolate the missing picture information, however they rather fall into the category of intelligent frame creation and require complex algorithms and substantial processing power.
Deinterlacing is only partly responsible for such lag; scaling also involves complex algorithms that take milliseconds to run.
Another option is to speed up 24-frame film by 4% (to 25 frames/s) for PAL/SECAM conversion; this method is still widely used for DVDs, as well as television broadcasts (SD & HD) in the PAL markets.
Most movies on Blu-rays have preserved the original non interlaced 24 frame/s motion film rate and allow output in the progressive 1080p24 format directly to display devices, with no conversion necessary.
TV production crews can also use special film cameras which operate at 25 or 30 frame/s, where such material does not need framerate conversion for broadcasting in the intended video system format.
However, if the interlaced signal was originally produced from a lower frame-rate source such as film, then no information is lost and these methods may suffice.
Talking about FPS, it is necessary to specify the resolution of all frames and hardware characteristics, because the speed of specific deinterlacing method significantly depends on these two factors.
FFmpeg Bob Weaver Deinterlacing Filter is the part of well-known framework for video and audio processing.
Vapoursynth EEDI3 is the abbreviation for "enhanced edge directed interpolation 3", authors of this method state that it works by finding the best non-decreasing warping between two lines according to a cost functional.
[citation needed] Using a computer for playback and/or processing potentially allows a broader choice of video players and/or editing software not limited to the quality offered by the embedded consumer electronics device, so at least theoretically higher deinterlacing quality is possible – especially if the user can pre-convert interlaced video to progressive scan before playback and advanced and time-consuming deinterlacing algorithms (i.e. employing the "production" method).
[14][15] The main argument was that no mattered how complex the deinterlacing algorithm may be, the artifacts in the interlaced signal cannot be eliminated because some information is lost between frames.
