Deinterlacing
Encyclopedia
Deinterlacing is the process of converting interlaced video, such as common analog television
signals or 1080i format HDTV signals, into a non-interlaced form.
Interlaced video frame consists of two sub-fields taken in sequence, each sequentially scanned at odd and even lines of the image sensor; analog television employed this technique because it allowed for less transmission bandwidth and further eliminated the perceived flicker that a similar frame rate would give using progressive scan. CRT based displays were able to display interlaced video correctly due to its complete analogue nature. All of the newer displays are inherently digital in that the display comprises discrete pixels. Consequently the two fields need to be combined into a single frame, which leads to various visual defects which the deinterlacing process should try to minimise.
Deinterlacing has been researched for decades and employs complex processing algorithms; however, consistent results have been very hard to achieve.
and photographic film
capture a series of frame
s (still images) in rapid succession; however, television systems read the captured image by serially scanning the image sensor
by lines (rows). In analog television, each frame is divided into two consecutive fields
, one containing all even lines, another with the odd lines. The fields are captured in succession at a rate twice that of the nominal frame rate. For instance, PAL
and SECAM
systems have a rate of 25 frames/s or 50 fields/s, while the NTSC
system delivers 29.97 frames/s or 59.94 fields/s. This process of dividing frames into half-resolution fields at double the frame rate is known as interlacing.
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. This results in an effective doubling of time resolution as compared with non-interlaced footage (for frame rates equal to field rates). However, interlaced signal requires a display that is natively capable to show 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.
Most modern displays, such as LCD, DLP and plasma display
s, are not able to work in interlaced mode, because they are fixed-resolution displays and only support progressive scanning. In order to display interlaced signal on such displays, the two interlaced fields must be converted to one progressive
frame with a process known as de-interlacing. 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.
There are several techniques available that extrapolate the missing picture information from the available picture information. These fall into the category of intelligent frame creation rather than true deinterlacing. The degree to which they succeed is a function of the processing power that is applied to the task. Further, the visible quality of the final video information is dependent on the quality of the input video. Currently, the biggest obstacle to an acceptable final picture is compression artifacts in the original video feed. Some of these systems are now good enough that even high bitrate (10 Mb/s or greater) 1080/25p video can be converted into 1080/50p video for display such that it is difficult to distinguish from original 1080/50p video.
Deinterlacing techniques require complex processing and thus can introduce a delay into the video feed. While not generally noticeable, this can result in the display of older video games lagging
behind controller input. Many TVs thus have a "game mode" in which minimal processing is done in order to maximize speed at the expense of image quality. Deinterlacing is only partly responsible for such lag; scaling
also involves complex algorithms that take precious milliseconds to run.
Typical movie material is shot on 24 frames/s film; when converting film to interlaced video using telecine
, each film frame can be presented by two progressive segmented frame
s (PsF). This format does not require complex deinterlacing algorithm because each field contains a part of the very same progressive frame. However to match 50 field interlaced PAL/SECAM or 59.94/60 field interlaced NTSC signal, frame rate conversion should be performed using various "pulldown" techniques; most advanced TV sets can restore the original 24 frame/s signal using an inverse telecine process. Another option is to speed up 24-frame film by 4% (to 25 frames/s) for PAL/SECAM conversion; this method is still vastly used for DVDs, as well as television broadcasts (SD & HD) in the PAL markets.
DVD
s can either encode movies using one of these methods, or store original 24 frame/s progressive video and use MPEG-2 decoder tags to instruct the video player on how to convert them to the interlaced format. Most movies on Blu-ray disc
s 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.
Some 1080i HDV camcorders also offer PsF mode with cinema-like frame rates of 24 or 25 frame/s. The TV production can also use special film cameras which operate at 25 or 30 frame/s; such material does not need framerate conversion for broadcasting in the intended video system format.
There are various methods to deinterlace video, each producing different problems or artifacts of its own. Some methods are much cleaner in artifacts than other methods.
Most deinterlacing techniques can be broken up into three different groups all using their own exact techniques. The first group are called field combination deinterlacers, because they take the even and odd fields and combine them into one frame which is then displayed. The second group are called field extension deinterlacers, because each field (with only half the lines) is extended to the entire screen to make a frame. The third type uses a combination of both and falls under the banner of motion compensation and a number of other names.
Modern deinterlacing systems therefore buffer several fields and use techniques like edge detection
in an attempt to find the motion between the fields. This is then used to interpolate the missing lines from the original field, reducing the combing effect.
Line doubling is sometimes confused with deinterlacing in general, or with interpolation
(image scaling) which uses spatial filtering to generate extra lines and hence reduce the visibility of pixelation on any type of display. The terminology 'line doubler' is used more frequently in high end consumer electronics, while 'deinterlacing' is used more frequently in the computer and digital video arena.
One of the basic hints to the direction and amount of motion would be the direction and length of combing artifacts in the interlaced signal. More advanced implementations would employ algorithms similar to block motion compensation
used in video compression; deinterlacers that use this technique are often superior because they can use information from many fields, as opposed to just one or two. This requires powerful hardware to achieve realtime operation.
For example, if two fields had a person's face moving to the left, weaving would create combing, and blending would create ghosting. Advanced motion compensation (ideally) would see that the face in several fields is the same image, just moved to a different position, and would try to detect direction and amount of such motion. The algorithm would then try to reconstruct the full detail of the face in both output frames by combining the images together, moving parts of each subfield along the detected direction by the detected amount of movement.
Motion compensation needs to be combined with scene change detection, otherwise it will attempt to find motion between two completely different scenes. A poorly implemented motion compensation algorithm would interfere with natural motion and could lead to visual artifacts which manifest as "jumping" parts in what should be a stationary or a smoothly moving image.
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 dinterlacing 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).
However, the quality of both free and commercial consumer-grade software may not be up to the level of professional software and equipment. Also, most users are not trained in video production; this often causes poor results as many people do not know much about deinterlacing and are unaware that the frame rate is half the field rate. Many codecs/players do not even deinterlace by themselves and rely on the graphics card and video acceleration API to do proper deinterlacing.
has argued against the use of interlaced video in production and broadcasting, recommending 720p 50 fps
(frames per second) as current production format and working with the industry to introduce 1080p
50 as a future-proof production standard which offers higher vertical resolution, better quality at lower bitrates, and easier conversion to other formats such as 720p50 and 1080i50. The main argument is that no matter how complex the deinterlacing algorithm may be, the artifacts in the interlaced signal cannot be completely eliminated because some information is lost between frames.
These algorithms display the video at the original half-picture rate, which is typically 50 (PAL) or 60 (NTSC) half-pictures per second. This is double the full picture rate, hence the name. This approach to deinterlacing is also known as field rendering.This group takes into account that the half-pictures of a true interlaced video were intended to be displayed at different times. This can make the motion look very smooth.Simple doublers (Bob and Linear) display only one half-picture at a time. Nevertheless, the quick alternating display produces a convincing illusion of full vertical resolution while playback is running.Some more advanced doublers (such as Yadif (2x)) are based on interpolators (see below), and attempt to generate full pictures to display. When interpolators are used in this way, which field is kept, alternates just like in the simple doublers.The last doubler (Phosphor) does not fit into either of these categories, but attempts to simulate a traditional CRT TV.All doublers can be used with both true interlaced and telecined video.
Here is the following methods from VLC:
Analog television
Analog television is the analog transmission that involves the broadcasting of encoded analog audio and analog video signal: one in which the message conveyed by the broadcast signal is a function of deliberate variations in the amplitude and/or frequency of the signal...
signals or 1080i format HDTV signals, into a non-interlaced form.
Interlaced video frame consists of two sub-fields taken in sequence, each sequentially scanned at odd and even lines of the image sensor; analog television employed this technique because it allowed for less transmission bandwidth and further eliminated the perceived flicker that a similar frame rate would give using progressive scan. CRT based displays were able to display interlaced video correctly due to its complete analogue nature. All of the newer displays are inherently digital in that the display comprises discrete pixels. Consequently the two fields need to be combined into a single frame, which leads to various visual defects which the deinterlacing process should try to minimise.
Deinterlacing has been researched for decades and employs complex processing algorithms; however, consistent results have been very hard to achieve.
Background
Both videoVideo
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
and photographic film
Film
A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...
capture a series of frame
Film frame
In filmmaking, video production, animation, and related fields, a film frame or video frame is one of the many still images which compose the complete moving picture...
s (still images) in rapid succession; however, television systems read the captured image by serially scanning the image sensor
Image sensor
An image sensor is a device that converts an optical image into an electronic signal. It is used mostly in digital cameras and other imaging devices...
by lines (rows). In analog television, each frame is divided into two consecutive fields
Field (video)
In video, a field is one of the many still images which are displayed sequentially to create the impression of motion on the screen. Two fields comprise one video frame...
, one containing all even lines, another with the odd lines. The fields are captured in succession at a rate twice that of the nominal frame rate. For instance, PAL
PAL
PAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system...
and SECAM
SECAM
SECAM, also written SÉCAM , is an analog color television system first used in France....
systems have a rate of 25 frames/s or 50 fields/s, while the NTSC
NTSC
NTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as...
system delivers 29.97 frames/s or 59.94 fields/s. This process of dividing frames into half-resolution fields at double the frame rate is known as interlacing.
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
Flicker (screen)
Flicker is a visible fading between cycles displayed on video displays, especially the refresh interval on cathode ray tube based computer screens. Flicker occurs on CRTs when they are driven at a low refresh rate, allowing the brightness to drop for time intervals sufficiently long to be noticed...
by taking advantage of the persistence of vision
Persistence of vision
Persistence of vision is the phenomenon of the eye by which an afterimage is thought to persist for approximately one twenty-fifth of a second on the retina....
effect. This results in an effective doubling of time resolution as compared with non-interlaced footage (for frame rates equal to field rates). However, interlaced signal requires a display that is natively capable to show the individual fields in a sequential order, and only traditional CRT
Cathode ray tube
The cathode ray tube is a vacuum tube containing an electron gun and a fluorescent screen used to view images. It has a means to accelerate and deflect the electron beam onto the fluorescent screen to create the images. The image may represent electrical waveforms , pictures , radar targets and...
-based TV sets are capable of displaying interlaced signal, due to the electronic scanning and lack of apparent fixed resolution.
Most modern displays, such as LCD, DLP and plasma display
Plasma display
A plasma display panel is a type of flat panel display common to large TV displays or larger. They are called "plasma" displays because the technology utilizes small cells containing electrically charged ionized gases, or what are in essence chambers more commonly known as fluorescent...
s, are not able to work in interlaced mode, because they are fixed-resolution displays and only support progressive scanning. In order to display interlaced signal on such displays, the two interlaced fields must be converted to one progressive
Progressive scan
Progressive scanning is a way of displaying, storing, or transmitting moving images in which all the lines of each frame are drawn in sequence...
frame with a process known as de-interlacing. 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.
There are several techniques available that extrapolate the missing picture information from the available picture information. These fall into the category of intelligent frame creation rather than true deinterlacing. The degree to which they succeed is a function of the processing power that is applied to the task. Further, the visible quality of the final video information is dependent on the quality of the input video. Currently, the biggest obstacle to an acceptable final picture is compression artifacts in the original video feed. Some of these systems are now good enough that even high bitrate (10 Mb/s or greater) 1080/25p video can be converted into 1080/50p video for display such that it is difficult to distinguish from original 1080/50p video.
Deinterlacing techniques require complex processing and thus can introduce a delay into the video feed. While not generally noticeable, this can result in the display of older video games lagging
Input lag
Display lag is a phenomenon associated with some types of LCD displays, and nearly all types of HDTVs, that refers to latency, or lag measured by the difference between the time a signal is input into a display and the time it is shown by the display. This lag time has been measured as high as...
behind controller input. Many TVs thus have a "game mode" in which minimal processing is done in order to maximize speed at the expense of image quality. Deinterlacing is only partly responsible for such lag; scaling
Video scaler
A video scaler is a device for converting video signals from one size or resolution to another: usually "upscaling" or "upconverting" a video signal from a low resolution to one of higher resolution A video scaler is a device for converting video signals from one size or resolution to another:...
also involves complex algorithms that take precious milliseconds to run.
Progressive source material
Interlaced video can carry progressive scan signal, and deinterlacing process should consider this as well.Typical movie material is shot on 24 frames/s film; when converting film to interlaced video using telecine
Telecine
Telecine is transferring motion picture film into video and is performed in a color suite. The term is also used to refer to the equipment used in the post-production process....
, each film frame can be presented by two progressive segmented frame
Progressive segmented frame
Progressive segmented Frame is a scheme designed to acquire, store, modify, and distribute progressive-scan video using interlaced equipment and media....
s (PsF). This format does not require complex deinterlacing algorithm because each field contains a part of the very same progressive frame. However to match 50 field interlaced PAL/SECAM or 59.94/60 field interlaced NTSC signal, frame rate conversion should be performed using various "pulldown" techniques; most advanced TV sets can restore the original 24 frame/s signal using an inverse telecine process. Another option is to speed up 24-frame film by 4% (to 25 frames/s) for PAL/SECAM conversion; this method is still vastly used for DVDs, as well as television broadcasts (SD & HD) in the PAL markets.
DVD
DVD
A DVD is an optical disc storage media format, invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. DVDs offer higher storage capacity than Compact Discs while having the same dimensions....
s can either encode movies using one of these methods, or store original 24 frame/s progressive video and use MPEG-2 decoder tags to instruct the video player on how to convert them to the interlaced format. Most movies on Blu-ray disc
Blu-ray Disc
Blu-ray Disc is an optical disc storage medium designed to supersede the DVD format. The plastic disc is 120 mm in diameter and 1.2 mm thick, the same size as DVDs and CDs. Blu-ray Discs contain 25 GB per layer, with dual layer discs being the norm for feature-length video discs...
s 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.
Some 1080i HDV camcorders also offer PsF mode with cinema-like frame rates of 24 or 25 frame/s. The TV production can also use special film cameras which operate at 25 or 30 frame/s; such material does not need framerate conversion for broadcasting in the intended video system format.
Deinterlacing methods
Deinterlacing requires the display to buffer one or more fields and recombine them into full frames. In theory this would be as simple as capturing one field and combining it with the next field to be received, producing a single frame. However, the originally recorded signal was produced as a series of fields, and any motion of the subjects during the short period between the fields is encoded into the display. When combined into a single frame, the slight differences between the two fields due to this motion results in a "combing" effect where alternate lines are slightly displaced from each other.There are various methods to deinterlace video, each producing different problems or artifacts of its own. Some methods are much cleaner in artifacts than other methods.
Most deinterlacing techniques can be broken up into three different groups all using their own exact techniques. The first group are called field combination deinterlacers, because they take the even and odd fields and combine them into one frame which is then displayed. The second group are called field extension deinterlacers, because each field (with only half the lines) is extended to the entire screen to make a frame. The third type uses a combination of both and falls under the banner of motion compensation and a number of other names.
Modern deinterlacing systems therefore buffer several fields and use techniques like edge detection
Edge detection
Edge detection is a fundamental tool in image processing and computer vision, particularly in the areas of feature detection and feature extraction, which aim at identifying points in a digital image at which the image brightness changes sharply or, more formally, has discontinuities...
in an attempt to find the motion between the fields. This is then used to interpolate the missing lines from the original field, reducing the combing effect.
Field combination deinterlacing
- Weaving is done by adding consecutive fields together. This is fine when the image hasn't changed between fields, but any change will result in artifacts known as "combing," when the pixels in one frame do not line up with the pixels in the other, forming a jagged edge. This technique retains the full vertical resolution at the expense of half the temporal resolution (motion).
- Blending is done by blending, or averaging consecutive fields to be displayed as one frame. Combing is avoided because the images are on top of each other. This instead leaves an artifact known as ghosting. The image loses vertical resolution and temporal resolution. This is often combined with a vertical resize so that the output has no numerical loss in vertical resolution. The problem with this is that there is a quality loss, because the image has been downsized then upsized. This loss in detail makes the image look softer. Blending also loses half the temporal resolution since two motion fields are combined into one frame.
- Selective blending, or smart blending or motion adaptive blending, is a combination of weaving and blending. As areas that haven't changed from frame to frame don't need any processing, the frames are woven and only the areas that need it are blended. This retains the full vertical resolution and half the temporal resolution, and it has fewer artifacts than weaving or blending because of the selective combination of both techniques.
- Inverse Telecine: TelecineTelecineTelecine is transferring motion picture film into video and is performed in a color suite. The term is also used to refer to the equipment used in the post-production process....
is used to convert a motion picture source at 24 frames per second to interlaced TV video in countries that use NTSC video system at 30 frames per second. Countries which use PAL at 25 frames per second do not use Telecine since motion picture sources are sped up 4% to achieve the needed 25 frames per second. If Telecine was used then it is possible to reverse the algorithm to obtain the original non-interlaced footage, which has a slower frame rate. In order for this to work, the exact telecine pattern must be known or guessed. Unlike most other deinterlacing methods, when it works, inverse telecine can perfectly recover the original progressive video stream. - Telecide-style algorithms: If the interlaced footage was generated from progressive frames at a slower frame rate (e.g. "cartoon pulldown"), then the exact original frames can be recovered by copying the missing field from a matching previous/next frame. In cases where there is no match (e.g. brief cartoon sequences with an elevated frame rate), then the filter falls back on another deinterlacing method such as blending or line-doubling. This means that the worst case for Telecide is occasional frames with ghosting or reduced resolution. By contrast, when more sophisticated motion-detection algorithms fail, they can introduce pixel artifacts that are unfaithful to the original material. For telecineTelecineTelecine is transferring motion picture film into video and is performed in a color suite. The term is also used to refer to the equipment used in the post-production process....
video, decimationDecimation (signal processing)In digital signal processing, decimation is a technique for reducing the number of samples in a discrete-time signal. The element which implements this technique is referred to as a decimator.Decimation is a two-step process:...
can be applied as a post-process to reduce the frame rate, and this combination is generally more robust than a simple inverse telecine, which fails when differently interlaced footage is spliced together.
Field extension deinterlacing
- Half-sizing displays each interlaced frame on its own, resulting in a video with half the vertical resolution of the original, unscaled. While this method retains all vertical resolution and all temporal resolution it is understandably not used for regular viewing because of its false aspect ratio. However, it can be successfully used to apply video filtersFilter (video)A video filter is a software component that is used to decode audio and video. Multiple filters can be used in a filter chain, in which each filter receives input from its previous-in-line filter upstream, processes the input and outputs the processed video to its next-in-line filter downstream...
which expect a noninterlaced frame, such as those exploiting information from neighbouring pixels (e.g., sharpening).
- Line doublingLine doublerA line doubler is a device used to deinterlace video signals prior to display.The main function of a line doubler is to take an interlaced video source which consists of a two-field frame and create a progressive scan output. This can produce a brighter, smoother, higher-resolution picture...
takes the lines of each interlaced field (consisting of only even or odd lines) and doubles them, filling the entire frame. This results in the video having a frame rate identical to the field rate, but each frame having half the vertical resolution, or resolution equal to that of each field that the frame was made from. Line doubling prevents combing artifacts but causes a noticeable reduction in picture quality since each frame displayed is doubled and really only at the original half field resolution. This is noticeable mostly on stationary objects since they appear to bob up and down. These techniques are also called bob deinterlacing and linear deinterlacing for this reason. Line doubling retains horizontal and temporal resolution at the expense of vertical resolution and bobbing artifacts on stationary and slower moving objects. A variant of this method discards one field out of each frame, halving temporal resolution.
Line doubling is sometimes confused with deinterlacing in general, or with interpolation
Interpolation
In the mathematical field of numerical analysis, interpolation is a method of constructing new data points within the range of a discrete set of known data points....
(image scaling) which uses spatial filtering to generate extra lines and hence reduce the visibility of pixelation on any type of display. The terminology 'line doubler' is used more frequently in high end consumer electronics, while 'deinterlacing' is used more frequently in the computer and digital video arena.
Motion detection
Best picture quality can be ensured by combining traditional field combination methods (weaving and blending) and frame extension methods (bob or line doubling) to create a high quality progressive video sequence; the best algorithms would also try to predict the direction and the amount of image motion between subsequent sub-fields in order to better blend the two subfields together.One of the basic hints to the direction and amount of motion would be the direction and length of combing artifacts in the interlaced signal. More advanced implementations would employ algorithms similar to block motion compensation
Motion compensation
Motion compensation is an algorithmic technique employed in the encoding of video data for video compression, for example in the generation of MPEG-2 files. Motion compensation describes a picture in terms of the transformation of a reference picture to the current picture. The reference picture...
used in video compression; deinterlacers that use this technique are often superior because they can use information from many fields, as opposed to just one or two. This requires powerful hardware to achieve realtime operation.
For example, if two fields had a person's face moving to the left, weaving would create combing, and blending would create ghosting. Advanced motion compensation (ideally) would see that the face in several fields is the same image, just moved to a different position, and would try to detect direction and amount of such motion. The algorithm would then try to reconstruct the full detail of the face in both output frames by combining the images together, moving parts of each subfield along the detected direction by the detected amount of movement.
Motion compensation needs to be combined with scene change detection, otherwise it will attempt to find motion between two completely different scenes. A poorly implemented motion compensation algorithm would interfere with natural motion and could lead to visual artifacts which manifest as "jumping" parts in what should be a stationary or a smoothly moving image.
Where deinterlacing is performed
Deinterlacing of an interlaced video signal can be done at various points in the TV production chain.Progressive media
Deinterlacing is required for interlaced archive programs when the broadcast format or media format is progressive, as in EDTV 576p or HDTV 720p50 broadcasting, or mobile DVB-H broadcasting; there are two ways to achieve this.- Production – The interlaced video material is converted to progressive scan during program production. This should typically yield the best possible quality, since videographers have access to expensive and powerful deinterlacing equipment and software and can deinterlace at the best possible quality, probably manually choosing the optimal deinterlacing method for each frame.
- Broadcasting – Real-time deinterlacing hardware converts interlaced programs to progressive scan immediately prior to broadcasting. Since the processing time is constrained by the frame rate and no human input is available, the quality of conversion is most likely inferior to the pre-production method; however, expensive and high-performance deinterlacing equipment may still yield good results when properly tuned.
Interlaced media
When the broadcast format or media format is interlaced, real-time deinterlacing should be performed by embedded circuitry in a set-top box, television, external video processor, DVD or DVR player, or TV tuner card. Since consumer electronics equipment is typically far cheaper, has considerably less processing power and uses simpler algorithms compared to professional deinterlacing equipment, the quality of deinterlacing may vary broadly and typical results are often poor even on high-end equipment.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 dinterlacing 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).
However, the quality of both free and commercial consumer-grade software may not be up to the level of professional software and equipment. Also, most users are not trained in video production; this often causes poor results as many people do not know much about deinterlacing and are unaware that the frame rate is half the field rate. Many codecs/players do not even deinterlace by themselves and rely on the graphics card and video acceleration API to do proper deinterlacing.
Concerns over effectiveness
The European Broadcasting UnionEuropean Broadcasting Union
The European Broadcasting Union is a confederation of 74 broadcasting organisations from 56 countries, and 49 associate broadcasters from a further 25...
has argued against the use of interlaced video in production and broadcasting, recommending 720p 50 fps
Frame rate
Frame rate is the frequency at which an imaging device produces unique consecutive images called frames. The term applies equally well to computer graphics, video cameras, film cameras, and motion capture systems...
(frames per second) as current production format and working with the industry to introduce 1080p
1080p
1080p is the shorthand identification for a set of HDTV high-definition video modes that are characterized by 1080 horizontal lines of resolution and progressive scan, meaning the image is not interlaced as is the case with the 1080i display standard....
50 as a future-proof production standard which offers higher vertical resolution, better quality at lower bitrates, and easier conversion to other formats such as 720p50 and 1080i50. The main argument is that no matter how complex the deinterlacing algorithm may be, the artifacts in the interlaced signal cannot be completely eliminated because some information is lost between frames.
Doublers
"Deinterlacing modes:" Bob, Linear, Yadif (2x) (v1.1.0+), Phosphor(v1.2.0+), best of them and the slowest are QTGMC (AviSynth).These algorithms display the video at the original half-picture rate, which is typically 50 (PAL) or 60 (NTSC) half-pictures per second. This is double the full picture rate, hence the name. This approach to deinterlacing is also known as field rendering.This group takes into account that the half-pictures of a true interlaced video were intended to be displayed at different times. This can make the motion look very smooth.Simple doublers (Bob and Linear) display only one half-picture at a time. Nevertheless, the quick alternating display produces a convincing illusion of full vertical resolution while playback is running.Some more advanced doublers (such as Yadif (2x)) are based on interpolators (see below), and attempt to generate full pictures to display. When interpolators are used in this way, which field is kept, alternates just like in the simple doublers.The last doubler (Phosphor) does not fit into either of these categories, but attempts to simulate a traditional CRT TV.All doublers can be used with both true interlaced and telecined video.
Here is the following methods from VLC:
| Algo | 4:2:0 | 4:2:2 | Algo type | Interpolation (if applic.) | Notes |
|---|---|---|---|---|---|
| C, H, FR | C, H, FR | ||||
| Discard | 0, h, 1x | 0, f, 1x | interpolator | none | keeps only top field; each line is repeated |
| Mean | 0, h, 1x | 2, h, 1x | blender | half-resolution blender; 1) | |
| Blend | 0, f, 1x | 0, f, 1x | blender | full-resolution blender; 2) | |
| Bob | 0, f, 2x | 0, f, 2x | doubler | none | each line is repeated; 3) |
| Linear | 0, f, 2x | 2, f, 2x | doubler | simple linear | first/last line copied; others interpolated; 3) |
| X | 0, f, 1x | 2, f, 1x | interpolator | MC + edge-oriented | keeps only top field in interlaced parts; 4) |
| Yadif | 0, f, 1x | 2, f, 1x | interpolator | spatial/temporal | keeps only top field in interlaced parts |
| Yadif (2x) | 0, f, 2x | 2, f, 2x | doubler | spatial/temporal | Yadif and Yadif (2x) come from MPlayer |
| Phosphor | 5), f, 2x | 2, f, 2x | doubler | CRT TV simulator; 6) | |
| IVTC | 0, f, 7) | 2, f, 7) | inverse telecine |
See also
- Interlaced video
- DCDi by FaroudjaDCDiDCDi by Faroudja is a digital enhancement method developed by Faroudja in 1996.DCDi technology is primarily used for improving the image quality of low resolution images...
- HDTV BlurHDTV blurHDTV blur is a common term used to describe a number of different artifacts on modern consumer high-definition television sets.The following factors are generally the primary or secondary causes of HDTV blur; in some cases more than one of these factors may be in play at the studio or receiver end...
- Refresh RateRefresh rateThe refresh rate is the number of times in a second that a display hardware draws the data...
- HDTV
External links
- 3:2 Pulldown and Deinterlacing (theprojectorpros.com)
- Stream Interlace and Deinterlace (planetmath.org)
- 'Format wars' – EBU document (with nice animation demonstrating interlace too)
- DVD progressive scanning – Deinterlacing and film-to-video conversion with respect to DVDs
- Frequently asked questions about deinterlacing
- 100fps Facts, solutions and examples of Deinterlacing.
- Deinterlacing filters Comparison of 17 different deinterlace filters.