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92-504: Composite video is an baseband analog video format that typically carries a 405 , 525 or 625 line interlaced black and white or color signal, on a single channel, unlike the higher-quality S-Video (two channels) and the even higher-quality YPbPr (three channels). A yellow RCA connector is typically used for composite video, with the audio being carried on separate additional L/R RCA connectors. In professional settings, or on devices that are too small for an RCA connector, such as

184-432: A 2.2 kHz audio tone produces a modulation index of 1.36. Suppose that we limit ourselves to only those sidebands that have a relative amplitude of at least 0.01. Then, examining the chart shows this modulation index will produce three sidebands. These three sidebands, when doubled, gives us (6 × 2.2 kHz) or a 13.2 kHz required bandwidth. A rule of thumb , Carson's rule states that nearly all (≈98 percent) of

276-586: A 5-pin DIN connector for audio. The BNC connector, in turn, post dated the PL-259 connector featured on first-generation VCRs. Video cables are 75 ohm impedance, low in capacitance. Typical values run from 52 pF/m for an HDPE -foamed dielectric precision video cable to 69 pF/m for a solid PE dielectric cable. The active image area of composite and s-video signals are digitally stored at 720x576i25 PAL and 720x480i29.7 (or 720x488) pixels. This does not represent

368-443: A baseband modulating signal may be approximated by a sinusoidal continuous wave signal with a frequency f m . This method is also named as single-tone modulation. The integral of such a signal x m ( t ) = c o s ( 2 π f m t ) {\displaystyle x_{m}(t)=cos(2\pi f_{m}t)} is: In this case, the expression for y(t) above simplifies to: where

460-435: A binary signal modulates the carrier, the modulation index is given by: where T s {\displaystyle T_{s}\,} is the symbol period, and f m = 1 2 T s {\displaystyle f_{m}={\frac {1}{2T_{s}}}\,} is used as the highest frequency of the modulating binary waveform by convention, even though it would be more accurate to say it

552-459: A closed-circuit system as an analog signal. Broadcast or studio cameras use a single or dual coaxial cable system using serial digital interface (SDI). See List of video connectors for information about physical connectors and related signal standards. Video may be transported over networks and other shared digital communications links using, for instance, MPEG transport stream , SMPTE 2022 and SMPTE 2110 . Digital television broadcasts use

644-522: A digital camera, other types of connectors can be used. Composite video is also known by the initials CVBS for Composite Video Baseband Signal or Color, Video, Blanking and Sync , or is simply referred to as SD video for the standard-definition television signal it conveys. There are three dominant variants of composite video signals, corresponding to the analog color system used ( NTSC , PAL , and SECAM ), but purely monochrome signals can also be used. A composite video signal combines, on one wire,

736-541: A functional relation to the modulating signal amplitude. Digital data can be encoded and transmitted with a type of frequency modulation known as frequency-shift keying (FSK), in which the instantaneous frequency of the carrier is shifted among a set of frequencies. The frequencies may represent digits, such as '0' and '1'. FSK is widely used in computer modems such as fax modems , telephone caller ID systems, garage door openers, and other low-frequency transmissions. Radioteletype also uses FSK. Frequency modulation

828-456: A lack of selectivity may cause one station to be overtaken by another on an adjacent channel . Frequency drift was a problem in early (or inexpensive) receivers; inadequate selectivity may affect any tuner. A wideband FM signal can also be used to carry a stereo signal; this is done with multiplexing and demultiplexing before and after the FM process. The FM modulation and demodulation process

920-433: A natively progressive broadcast or recorded signal, the result is the optimum spatial resolution of both the stationary and moving parts of the image. Interlacing was invented as a way to reduce flicker in early mechanical and CRT video displays without increasing the number of complete frames per second . Interlacing retains detail while requiring lower bandwidth compared to progressive scanning. In interlaced video,

1012-442: A number is available. Analog video is a video signal represented by one or more analog signals . Analog color video signals include luminance (Y) and chrominance (C). When combined into one channel, as is the case among others with NTSC , PAL , and SECAM , it is called composite video . Analog video may be carried in separate channels, as in two-channel S-Video (YC) and multi-channel component video formats. Analog video

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1104-438: A particular refresh rate, display resolution , and color space . Many analog and digital recording formats are in use, and digital video clips can also be stored on a computer file system as files, which have their own formats. In addition to the physical format used by the data storage device or transmission medium, the stream of ones and zeros that is sent must be in a particular digital video coding format , for which

1196-433: A photoconductive plate with the desired image and produce a voltage signal proportional to the brightness in each part of the image. The signal could then be sent to televisions, where another beam would receive and display the image. Charles Ginsburg led an Ampex research team to develop one of the first practical video tape recorders (VTR). In 1951, the first VTR captured live images from television cameras by writing

1288-512: A ratio between width and height. The ratio of width to height for a traditional television screen is 4:3, or about 1.33:1. High-definition televisions use an aspect ratio of 16:9, or about 1.78:1. The aspect ratio of a full 35 mm film frame with soundtrack (also known as the Academy ratio ) is 1.375:1. Pixels on computer monitors are usually square, but pixels used in digital video often have non-square aspect ratios, such as those used in

1380-406: A sampled signal and losslessly reproduces composite video signals using PCM encoding of the analog signal on the magnetic tape . With the advent of affordable higher sampling speed analog to digital converters, realtime composite to YUV sampled digital sampling has been possible since the 1980s and raw waveform sampling and software decoding since the 2010s. A number of so-called extensions to

1472-489: A scientific and technical conversation in the Nizhny Novgorod Radio Laboratory , reported about his new method of telephony, based on a change in the period of oscillations. Demonstration of frequency modulation was carried out on the laboratory model. Frequency modulated systems are a widespread and commercially available assistive technology that make speech more understandable by improving

1564-425: A signal from an analog modulator. However, composite video has an established market for both devices that convert it to channel 3/4 outputs , as well as devices that convert standards like VGA to composite, therefore it has offered opportunities to repurpose older composite monitors for newer devices. The process of modulating RF with the original video signal, and then demodulating the original signal again in

1656-401: A signal in (roughly) composite format: LaserDiscs and type C videotape for example store a true composite signal modulated, while consumer videotape formats (including VHS and Betamax ) and commercial and industrial tape formats (including U-matic ) use modified composite signals FM encoded (generally known as color-under ). The professional D-2 videocassette format digitally storing

1748-465: A target, its outgoing sounds return as echoes, which are Doppler-shifted upward in frequency. In certain species of bats, which produce constant frequency (CF) echolocation calls, the bats compensate for the Doppler shift by lowering their call frequency as they approach a target. This keeps the returning echo in the same frequency range of the normal echolocation call. This dynamic frequency modulation

1840-470: A tone-modulated FM wave, if the modulation frequency is held constant and the modulation index is increased, the (non-negligible) bandwidth of the FM signal increases but the spacing between spectra remains the same; some spectral components decrease in strength as others increase. If the frequency deviation is held constant and the modulation frequency increased, the spacing between spectra increases. Frequency modulation can be classified as narrowband if

1932-414: A wider signal bandwidth than amplitude modulation by an equivalent modulating signal; this also makes the signal more robust against noise and interference . Frequency modulation is also more robust against signal-amplitude-fading phenomena. As a result, FM was chosen as the modulation standard for high frequency, high fidelity radio transmission, hence the term " FM radio " (although for many years

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2024-434: Is broadcast over FM radio . However, under severe enough multipath conditions it performs much more poorly than AM, with distinct high frequency noise artifacts that are audible with lower volumes and less complex tones. With high enough volume and carrier deviation audio distortion starts to occur that otherwise wouldn't be present without multipath or with an AM signal. Frequency modulation and phase modulation are

2116-512: Is called the Doppler Shift Compensation (DSC), and was discovered by Hans Schnitzler in 1968. FM is also used at intermediate frequencies by analog VCR systems (including VHS ) to record the luminance (black and white) portions of the video signal. Commonly, the chrominance component is recorded as a conventional AM signal, using the higher-frequency FM signal as bias . FM is the only feasible method of recording

2208-418: Is identical in stereo and monaural processes. FM is commonly used at VHF radio frequencies for high-fidelity broadcasts of music and speech . In broadcast services, where audio fidelity is important, wideband FM is generally used. Analog TV sound is also broadcast using FM. Narrowband FM is used for voice communications in commercial and amateur radio settings. In two-way radio , narrowband FM (NBFM)

2300-456: Is in rough chronological order. All formats listed were sold to and used by broadcasters, video producers, or consumers; or were important historically. Digital video tape recorders offered improved quality compared to analog recorders. Optical storage mediums offered an alternative, especially in consumer applications, to bulky tape formats. A video codec is software or hardware that compresses and decompresses digital video . In

2392-455: Is less sensitive to details in color than brightness, the luminance data for all pixels is maintained, while the chrominance data is averaged for a number of pixels in a block, and the same value is used for all of them. For example, this results in a 50% reduction in chrominance data using 2-pixel blocks (4:2:2) or 75% using 4-pixel blocks (4:2:0). This process does not reduce the number of possible color values that can be displayed, but it reduces

2484-517: Is often described as 576i50 , where 576 indicates the total number of horizontal scan lines, i indicates interlacing, and 50 indicates 50 fields (half-frames) per second. When displaying a natively interlaced signal on a progressive scan device, the overall spatial resolution is degraded by simple line doubling —artifacts, such as flickering or "comb" effects in moving parts of the image that appear unless special signal processing eliminates them. A procedure known as deinterlacing can optimize

2576-527: Is reduced by registering differences between parts of a single frame; this task is known as intraframe compression and is closely related to image compression . Likewise, temporal redundancy can be reduced by registering differences between frames; this task is known as interframe compression , including motion compensation and other techniques. The most common modern compression standards are MPEG-2 , used for DVD , Blu-ray, and satellite television , and MPEG-4 , used for AVCHD , mobile phones (3GP), and

2668-487: Is reduced to an acceptable level. FM is also used at audio frequencies to synthesize sound. This technique, known as FM synthesis , was popularized by early digital synthesizers and became a standard feature in several generations of personal computer sound cards . Edwin Howard Armstrong (1890–1954) was an American electrical engineer who invented wideband frequency modulation (FM) radio. He patented

2760-422: Is shot at a slower frame rate of 24 frames per second, which slightly complicates the process of transferring a cinematic motion picture to video. The minimum frame rate to achieve a comfortable illusion of a moving image is about sixteen frames per second. Video can be interlaced or progressive . In progressive scan systems, each refresh period updates all scan lines in each frame in sequence. When displaying

2852-438: Is that decompressed video has lower quality than the original, uncompressed video because there is insufficient information to accurately reconstruct the original video. FM (modulation) In analog frequency modulation, such as radio broadcasting, of an audio signal representing voice or music, the instantaneous frequency deviation , i.e. the difference between the frequency of the carrier and its center frequency, has

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2944-405: Is the frequency deviation , which represents the maximum shift away from f c in one direction, assuming x m ( t ) is limited to the range ±1. It is important to realize that this process of integrating the instantaneous frequency to create an instantaneous phase is quite different from what the term "frequency modulation" naively implies, namely directly adding the modulating signal to

3036-466: Is the Deviation ratio which is the ratio of frequency deviation to highest frequency of modulating non-sinusoidal signal. FM provides improved signal-to-noise ratio (SNR), as compared for example with AM . Compared with an optimum AM scheme, FM typically has poorer SNR below a certain signal level called the noise threshold, but above a higher level – the full improvement or full quieting threshold –

3128-486: Is the Modulation index which is the ratio of frequency deviation to highest frequency in the modulating signal and f m {\displaystyle f_{m}\,} is the highest frequency in the modulating signal. Condition for application of Carson's rule is only sinusoidal signals. For non-sinusoidal signals: where W is the highest frequency in the modulating signal but non-sinusoidal in nature and D

3220-468: Is the highest fundamental of the modulating binary waveform. In the case of digital modulation, the carrier f c {\displaystyle f_{c}\,} is never transmitted. Rather, one of two frequencies is transmitted, either f c + Δ f {\displaystyle f_{c}+\Delta f} or f c − Δ f {\displaystyle f_{c}-\Delta f} , depending on

3312-416: Is used for FM broadcasting , in which music and speech are transmitted with up to 75 kHz deviation from the center frequency and carry audio with up to a 20 kHz bandwidth and subcarriers up to 92 kHz. For the case of a carrier modulated by a single sine wave, the resulting frequency spectrum can be calculated using Bessel functions of the first kind, as a function of the sideband number and

3404-509: Is used in NTSC television, YUV is used in PAL television, YDbDr is used by SECAM television, and YCbCr is used for digital video. The number of distinct colors a pixel can represent depends on the color depth expressed in the number of bits per pixel. A common way to reduce the amount of data required in digital video is by chroma subsampling (e.g., 4:4:4, 4:2:2, etc.). Because the human eye

3496-440: Is used in both consumer and professional television production applications. Digital video signal formats have been adopted, including serial digital interface (SDI), Digital Visual Interface (DVI), High-Definition Multimedia Interface (HDMI) and DisplayPort Interface. Video can be transmitted or transported in a variety of ways including wireless terrestrial television as an analog or digital signal, coaxial cable in

3588-586: Is used to conserve bandwidth for land mobile, marine mobile and other radio services. A high-efficiency radio-frequency switching amplifier can be used to transmit FM signals (and other constant-amplitude signals ). For a given signal strength (measured at the receiver antenna), switching amplifiers use less battery power and typically cost less than a linear amplifier . This gives FM another advantage over other modulation methods requiring linear amplifiers, such as AM and QAM . There are reports that on October 5, 1924, Professor Mikhail A. Bonch-Bruevich , during

3680-523: Is widely used for FM radio broadcasting . It is also used in telemetry , radar , seismic prospecting, and monitoring newborns for seizures via EEG , two-way radio systems, sound synthesis , magnetic tape-recording systems and some video-transmission systems. In radio transmission, an advantage of frequency modulation is that it has a larger signal-to-noise ratio and therefore rejects radio frequency interference better than an equal power amplitude modulation (AM) signal. For this reason, most music

3772-634: The BBC called it "VHF radio" because commercial FM broadcasting uses part of the VHF band – the FM broadcast band ). FM receivers employ a special detector for FM signals and exhibit a phenomenon known as the capture effect , in which the tuner "captures" the stronger of two stations on the same frequency while rejecting the other (compare this with a similar situation on an AM receiver, where both stations can be heard simultaneously). Frequency drift or

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3864-405: The FM capture effect removes print-through and pre-echo . A continuous pilot-tone, if added to the signal – as was done on V2000 and many Hi-band formats – can keep mechanical jitter under control and assist timebase correction . These FM systems are unusual, in that they have a ratio of carrier to maximum modulation frequency of less than two; contrast this with FM audio broadcasting, where

3956-502: The Latin video (I see). Video developed from facsimile systems developed in the mid-19th century. Early mechanical video scanners, such as the Nipkow disk , were patented as early as 1884, however, it took several decades before practical video systems could be developed, many decades after film . Film records using a sequence of miniature photographic images visible to the eye when

4048-503: The MPEG-2 and other video coding formats and include: Analog television broadcast standards include: An analog video format consists of more information than the visible content of the frame. Preceding and following the image are lines and pixels containing metadata and synchronization information. This surrounding margin is known as a blanking interval or blanking region ; the horizontal and vertical front porch and back porch are

4140-625: The sinusoidal carrier is x c ( t ) = A c cos ⁡ ( 2 π f c t ) {\displaystyle x_{c}(t)=A_{c}\cos(2\pi f_{c}t)\,} , where f c is the carrier's base frequency, and A c is the carrier's amplitude, the modulator combines the carrier with the baseband data signal to get the transmitted signal: where f Δ = K f A m {\displaystyle f_{\Delta }=K_{f}A_{m}} , K f {\displaystyle K_{f}} being

4232-462: The AM and FM bands. A gated and filtered signal derived from the color subcarrier , called the burst or colorburst , is added to the horizontal blanking interval of each line (excluding lines in the vertical sync interval ) as a synchronizing signal and amplitude reference for the chrominance signals. In NTSC composite video, the 3.58 MHz burst signal is inverted in phase (180° out of phase) from

4324-468: The Internet. Stereoscopic video for 3D film and other applications can be displayed using several different methods: Different layers of video transmission and storage each provide their own set of formats to choose from. For transmission, there is a physical connector and signal protocol (see List of video connectors ). A given physical link can carry certain display standards that specify

4416-493: The PAL and NTSC variants of the CCIR 601 digital video standard and the corresponding anamorphic widescreen formats. The 720 by 480 pixel raster uses thin pixels on a 4:3 aspect ratio display and fat pixels on a 16:9 display. The popularity of viewing video on mobile phones has led to the growth of vertical video . Mary Meeker , a partner at Silicon Valley venture capital firm Kleiner Perkins Caufield & Byers , highlighted

4508-755: The SNR is much improved over AM. The improvement depends on modulation level and deviation. For typical voice communications channels, improvements are typically 5–15 dB. FM broadcasting using wider deviation can achieve even greater improvements. Additional techniques, such as pre-emphasis of higher audio frequencies with corresponding de-emphasis in the receiver, are generally used to improve overall SNR in FM circuits. Since FM signals have constant amplitude, FM receivers normally have limiters that remove AM noise, further improving SNR. FM signals can be generated using either direct or indirect frequency modulation: Many FM detector circuits exist. A common method for recovering

4600-517: The TV, introduces losses including added noise or interference. For these reasons, it is best to use composite connections instead of RF connections if possible for live signals and sample the source FM RF signal for recorded formats. Some video equipment and modern televisions have only RF input. Video#Analog video Video is an electronic medium for the recording, copying , playback, broadcasting , and display of moving visual media . Video

4692-457: The amplitude A m {\displaystyle A_{m}\,} of the modulating sinusoid is represented in the peak deviation f Δ = K f A m {\displaystyle f_{\Delta }=K_{f}A_{m}} (see frequency deviation ). The harmonic distribution of a sine wave carrier modulated by such a sinusoidal signal can be represented with Bessel functions ; this provides

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4784-402: The basis for a mathematical understanding of frequency modulation in the frequency domain. As in other modulation systems, the modulation index indicates by how much the modulated variable varies around its unmodulated level. It relates to variations in the carrier frequency : where f m {\displaystyle f_{m}\,} is the highest frequency component present in

4876-405: The binary state 0 or 1 of the modulation signal. If h ≫ 1 {\displaystyle h\gg 1} , the modulation is called wideband FM and its bandwidth is approximately 2 f Δ {\displaystyle 2f_{\Delta }\,} . While wideband FM uses more bandwidth, it can improve the signal-to-noise ratio significantly; for example, doubling

4968-450: The building blocks of the blanking interval. Computer display standards specify a combination of aspect ratio, display size, display resolution, color depth, and refresh rate. A list of common resolutions is available. Early television was almost exclusively a live medium, with some programs recorded to film for historical purposes using Kinescope . The analog video tape recorder was commercially introduced in 1951. The following list

5060-425: The camera's electrical signal onto magnetic videotape . Video recorders were sold for $ 50,000 in 1956, and videotapes cost US$ 300 per one-hour reel. However, prices gradually dropped over the years; in 1971, Sony began selling videocassette recorder (VCR) decks and tapes into the consumer market . Digital video is capable of higher quality and, eventually, a much lower cost than earlier analog technology. After

5152-575: The carrier frequency which would result in a modulated signal that has spurious local minima and maxima that do not correspond to those of the carrier. While most of the energy of the signal is contained within f c ± f Δ , it can be shown by Fourier analysis that a wider range of frequencies is required to precisely represent an FM signal. The frequency spectrum of an actual FM signal has components extending infinitely, although their amplitude decreases and higher-order components are often neglected in practical design problems. Mathematically,

5244-482: The change in the carrier frequency is about the same as the signal frequency, or as wideband if the change in the carrier frequency is much higher (modulation index > 1) than the signal frequency. For example, narrowband FM (NFM) is used for two-way radio systems such as Family Radio Service , in which the carrier is allowed to deviate only 2.5 kHz above and below the center frequency with speech signals of no more than 3.5 kHz bandwidth. Wideband FM

5336-460: The chrominance and luminance components of the signal. This is usually seen when chrominance is transmitted with high bandwidth, and its spectrum reaches into the band of the luminance frequencies. Comb filters are commonly used to separate signals and eliminate these artifacts from composite sources. S-Video and component video avoid this problem as they maintain the component signals physically separate. Most home analog video equipment record

5428-562: The commercial introduction of the DVD in 1997 and later the Blu-ray Disc in 2006, sales of videotape and recording equipment plummeted. Advances in computer technology allow even inexpensive personal computers and smartphones to capture, store, edit, and transmit digital video, further reducing the cost of video production and allowing programmers and broadcasters to move to tapeless production . The advent of digital broadcasting and

5520-461: The composite video signal is typically connected using an RCA connector, normally yellow. It is often accompanied with red and white connectors for right and left audio channels respectively. BNC connectors and higher quality coaxial cable are often used in professional television studios and post-production applications. BNC connectors were also used for composite video connections on early home VCRs , often accompanied by either RCA connector or

5612-438: The context of video compression, codec is a portmanteau of encoder and decoder , while a device that only compresses is typically called an encoder , and one that only decompresses is a decoder . The compressed data format usually conforms to a standard video coding format . The compression is typically lossy , meaning that the compressed video lacks some information present in the original video. A consequence of this

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5704-470: The demodulation may be carried out by using the Hilbert transform (implemented as a filter) to recover the instantaneous phase, and thereafter differentiating this phase (using another filter) to recover the instantaneous frequency. Alternatively, a complex mixer followed by a bandpass filter may be used to translate the signal to baseband, and then proceeding as before. When an echolocating bat approaches

5796-509: The display of an interlaced video signal from an analog, DVD, or satellite source on a progressive scan device such as an LCD television , digital video projector , or plasma panel. Deinterlacing cannot, however, produce video quality that is equivalent to true progressive scan source material. Aspect ratio describes the proportional relationship between the width and height of video screens and video picture elements. All popular video formats are rectangular , and this can be described by

5888-687: The entire composite signal. This can then be comb-filtered or chroma-decoded to a color image on a standard computer or via DAC played back to a TV. Composite is no longer the universal standard it once was for consumers after the digital era began phasing out analog CRT displays and virtually all consumer devices moved to using HDMI . Modified versions of composite such as 960H (960x576) are still in wide use for CCTV systems today in consumer use alongside fpv drones . Some devices, such as videocassette recorders (VCRs), video game consoles , and home computers output composite video. This may then be converted to FM RF with an RF modulator that generates

5980-445: The fields one at a time, rather than dividing up a complete frame after it is captured, the frame rate for motion is effectively doubled as well, resulting in smoother, more lifelike reproduction of rapidly moving parts of the image when viewed on an interlaced CRT display. NTSC, PAL, and SECAM are interlaced formats. Abbreviated video resolution specifications often include an i to indicate interlacing. For example, PAL video format

6072-441: The film is physically examined. Video, by contrast, encodes images electronically, turning the images into analog or digital electronic signals for transmission or recording. Video technology was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) television systems. Video was originally exclusively live technology. Live video cameras used an electron beam, which would scan

6164-466: The growth of vertical video viewing in her 2015 Internet Trends Report – growing from 5% of video viewing in 2010 to 29% in 2015. Vertical video ads like Snapchat 's are watched in their entirety nine times more frequently than landscape video ads. The color model uses the video color representation and maps encoded color values to visible colors reproduced by the system. There are several such representations in common use: typically, YIQ

6256-446: The harmonics in the baseband luma signal, rather than both being in separate continuous frequency bands alongside each other in the frequency domain. The signals may be separated using a comb filter . In other words, the combination of luma and chrominance is indeed a frequency-division technique, but it is much more complex than typical frequency-division multiplexing systems like the one used to multiplex analog radio stations on both

6348-432: The horizontal scan lines of each complete frame are treated as if numbered consecutively and captured as two fields : an odd field (upper field) consisting of the odd-numbered lines and an even field (lower field) consisting of the even-numbered lines. Analog display devices reproduce each frame, effectively doubling the frame rate as far as perceptible overall flicker is concerned. When the image capture device acquires

6440-579: The information signal is through a Foster–Seeley discriminator or ratio detector . A phase-locked loop can be used as an FM demodulator. Slope detection demodulates an FM signal by using a tuned circuit which has its resonant frequency slightly offset from the carrier. As the frequency rises and falls the tuned circuit provides a changing amplitude of response, converting FM to AM. AM receivers may detect some FM transmissions by this means, although it does not provide an efficient means of detection for FM broadcasts. In Software-Defined Radio implementations

6532-444: The luminance ("black-and-white") component of video to (and retrieving video from) magnetic tape without distortion; video signals have a large range of frequency components – from a few hertz to several megahertz , too wide for equalizers to work with due to electronic noise below −60  dB . FM also keeps the tape at saturation level, acting as a form of noise reduction ; a limiter can mask variations in playback output, and

6624-406: The modulated color signal overlaps that of the baseband signal, and separation relies on the fact that frequency components of the baseband signal tend to be near harmonics of the horizontal scanning rate, while the color carrier is selected to be an odd multiple of half the horizontal scanning rate; this produces a modulated color signal that consists mainly of harmonic frequencies that fall between

6716-402: The modulating signal x m ( t ), and Δ f {\displaystyle \Delta {}f\,} is the peak frequency-deviation – i.e. the maximum deviation of the instantaneous frequency from the carrier frequency. For a sine wave modulation, the modulation index is seen to be the ratio of the peak frequency deviation of the carrier wave to the frequency of

6808-536: The modulating sine wave. If h ≪ 1 {\displaystyle h\ll 1} , the modulation is called narrowband FM (NFM), and its bandwidth is approximately 2 f m {\displaystyle 2f_{m}\,} . Sometimes modulation index h < 0.3 {\displaystyle h<0.3}  is considered NFM and other modulation indices are considered wideband FM (WFM or FM). For digital modulation systems, for example, binary frequency shift keying (BFSK), where

6900-448: The modulation index. The carrier and sideband amplitudes are illustrated for different modulation indices of FM signals. For particular values of the modulation index, the carrier amplitude becomes zero and all the signal power is in the sidebands. Since the sidebands are on both sides of the carrier, their count is doubled, and then multiplied by the modulating frequency to find the bandwidth. For example, 3 kHz deviation modulated by

6992-639: The number of distinct points at which the color changes. Video quality can be measured with formal metrics like peak signal-to-noise ratio (PSNR) or through subjective video quality assessment using expert observation. Many subjective video quality methods are described in the ITU-T recommendation BT.500 . One of the standardized methods is the Double Stimulus Impairment Scale (DSIS). In DSIS, each expert views an unimpaired reference video, followed by an impaired version of

7084-505: The power of a frequency-modulated signal lies within a bandwidth B T {\displaystyle B_{T}\,} of: where Δ f {\displaystyle \Delta f\,} , as defined above, is the peak deviation of the instantaneous frequency f ( t ) {\displaystyle f(t)\,} from the center carrier frequency f c {\displaystyle f_{c}} , β {\displaystyle \beta }

7176-674: The proper carrier (often for channel 3 or 4 in North America , channel 36 in Europe ). Sometimes this modulator is built into the product (such as video game consoles, VCRs, or the Atari , Commodore 64 , or TRS-80 CoCo home-computers), is an external unit powered by the computer ( TI-99/4A ), or with an independent power supply. Because of the digital television transition most television sets no longer have analog television tuners but DVB-T and ATSC digital ones. They therefore cannot accept

7268-411: The ratio is around 10,000. Consider, for example, a 6-MHz carrier modulated at a 3.5-MHz rate; by Bessel analysis, the first sidebands are on 9.5 and 2.5 MHz and the second sidebands are on 13 MHz and −1 MHz. The result is a reversed-phase sideband on +1 MHz; on demodulation, this results in unwanted output at 6 – 1 = 5 MHz. The system must be designed so that this unwanted output

7360-407: The reference subcarrier. In PAL, the phase of the 4.43 MHz color subcarrier alternates on successive lines. In SECAM, no colorburst is used since phase information is irrelevant. The combining of component signals to form the composite signal does the same, causing a checkerboard video artifact known as dot crawl . Dot crawl is a defect that results from crosstalk due to the intermodulation of

7452-619: The regenerative circuit in 1914, the superheterodyne receiver in 1918 and the super-regenerative circuit in 1922. Armstrong presented his paper, "A Method of Reducing Disturbances in Radio Signaling by a System of Frequency Modulation", (which first described FM radio) before the New York section of the Institute of Radio Engineers on November 6, 1935. The paper was published in 1936. As the name implies, wideband FM (WFM) requires

7544-436: The same video. The expert then rates the impaired video using a scale ranging from "impairments are imperceptible" to "impairments are very annoying." Uncompressed video delivers maximum quality, but at a very high data rate . A variety of methods are used to compress video streams, with the most effective ones using a group of pictures (GOP) to reduce spatial and temporal redundancy . Broadly speaking, spatial redundancy

7636-404: The sensitivity of the frequency modulator and A m {\displaystyle A_{m}} being the amplitude of the modulating signal or baseband signal. In this equation, f ( τ ) {\displaystyle f(\tau )\,} is the instantaneous frequency of the oscillator and f Δ {\displaystyle f_{\Delta }\,}

7728-575: The signal-to-noise ratio in the user's ear. They are also called auditory trainers , a term which refers to any sound amplification system not classified as a hearing aid . They intensify signal levels from the source by 15 to 20 decibels. FM systems are used by hearing-impaired people as well as children whose listening is affected by disorders such as auditory processing disorder or ADHD . For people with sensorineural hearing loss , FM systems result in better speech perception than hearing aids. They can be coupled with behind-the-ear hearing aids to allow

7820-455: The subsequent digital television transition are in the process of relegating analog video to the status of a legacy technology in most parts of the world. The development of high-resolution video cameras with improved dynamic range and color gamuts , along with the introduction of high-dynamic-range digital intermediate data formats with improved color depth , has caused digital video technology to converge with film technology. Since 2013,

7912-459: The two complementary principal methods of angle modulation ; phase modulation is often used as an intermediate step to achieve frequency modulation. These methods contrast with amplitude modulation , in which the amplitude of the carrier wave varies, while the frequency and phase remain constant. If the information to be transmitted (i.e., the baseband signal ) is x m ( t ) {\displaystyle x_{m}(t)} and

8004-567: The use of digital cameras in Hollywood has surpassed the use of film cameras. Frame rate , the number of still pictures per unit of time of video, ranges from six or eight frames per second ( frame/s ) for old mechanical cameras to 120 or more frames per second for new professional cameras. PAL standards (Europe, Asia, Australia, etc.) and SECAM (France, Russia, parts of Africa, etc.) specify 25 frame/s, while NTSC standards (United States, Canada, Japan, etc.) specify 29.97 frame/s. Film

8096-434: The value of Δ f {\displaystyle \Delta {}f\,} , while keeping f m {\displaystyle f_{m}} constant, results in an eight-fold improvement in the signal-to-noise ratio. (Compare this with chirp spread spectrum , which uses extremely wide frequency deviations to achieve processing gains comparable to traditional, better-known spread-spectrum modes). With

8188-420: The video information required to recreate a color picture, as well as line and frame synchronization pulses. The color video signal is a linear combination of the luminance (Y) of the picture and a chrominance subcarrier which carries the color information (C), a combination of hue and saturation . Details of the combining process vary between the NTSC, PAL and SECAM systems. The frequency spectrum of

8280-514: The visible TV image can be transmitted using composite video. Since TV screens hide the vertical blanking interval of a composite video signal, these take advantage of the unseen parts of the signal. Examples of extensions include teletext , closed captioning , information regarding the show title, a set of reference colors that allows TV sets to automatically correct NTSC hue maladjustments, widescreen signaling (WSS) for switching between 4:3 and 16:9 display formats, etc. In home applications,

8372-474: The whole signal. Hardware typically samples at four times the color subcarrier frequency (4fsc) that includes the vertical blanking interval (VBI). Only commercial video capture devices used in broadcast output images with the extra VBI space. Direct sampling with high-speed ADCs and software time base correction has allowed projects like the open-source CVBS-Decode to create a D-2 like 4fsc stream that preserves and allows full presentation and inspection of

8464-526: Was first developed for mechanical television systems, which were quickly replaced by cathode-ray tube (CRT) systems, which, in turn, were replaced by flat-panel displays of several types. Video systems vary in display resolution , aspect ratio , refresh rate , color capabilities, and other qualities. Analog and digital variants exist and can be carried on a variety of media, including radio broadcasts , magnetic tape , optical discs , computer files , and network streaming . The word video comes from

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