Broadcast-safe video (broadcast legal or legal signal) is a term used in the

broadcast Broadcasting is the data distribution, distribution of sound, audio audiovisual content to dispersed audiences via a electronic medium (communication), mass communications medium, typically one using the electromagnetic spectrum (radio waves), ...

industry to define

video Video is an Electronics, electronic medium for the recording, copying, playback, broadcasting, and display of moving picture, moving image, visual Media (communication), media. Video was first developed for mechanical television systems, whi ...

and

audio Audio most commonly refers to sound, as it is transmitted in signal form. It may also refer to: Sound *Audio signal, an electrical representation of sound *Audio frequency, a frequency in the audio spectrum *Digital audio, representation of sound ...

compliant with the technical or regulatory broadcast requirements of the target area or region the feed might be broadcasting to. In the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, the

Federal Communications Commission The Federal Communications Commission (FCC) is an independent agency of the United States government that regulates communications by radio, television, wire, internet, wi-fi, satellite, and cable across the United States. The FCC maintains j ...

(FCC) is the regulatory authority; in most of

Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...

, standards are set by the

European Broadcasting Union The European Broadcasting Union (EBU; , UER) is an alliance of Public broadcasting, public service media organisations in countries within the European Broadcasting Area (EBA) or who are member states of the Council of Europe, members of the ...

(EBU).

Broadcast safe video

Broadcast safe standard-definition video

Broadcast safe 625 video

Broadcast safe standards for 625 lines of

standard-definition Standard-definition television (SDTV; also standard definition or SD) is a television system that uses a resolution that is not considered to be either high-definition television, high or enhanced definition. ''Standard'' refers to offering a ...

(Inaccurately referred to as

PAL Phase Alternating Line (PAL) is a color encoding system for analog television. It was one of three major analogue colour television standards, the others being NTSC and SECAM. In most countries it was broadcast at 625 lines, 50 fields (25 ...

, a colour encoding that is usually used with such systems)

are: * Common name = 625/50i (

576i 576i is a standard-definition television, standard-definition digital video mode, originally used for Digitization, digitizing 625 lines, 625 line Analog television, analogue television in most countries of the world where the utility frequen ...

) * Commonly used digital SD SDI baseband signal =

SMPTE 259M-C SMPTE 259M is a standard published by SMPTE which "describes a 10-bit serial digital interface operating at 143/270/360 Mb/s." The goal of SMPTE 259M is to define a serial digital interface (based on a coaxial cable), called SDI or SD-SDI. ...

, 270 Mbit/s bitrate * Commonly used No. of Vertical Lines = 625 (576 visible active video) * Commonly used Frame rate = 25 Hz (25 interlaced frame/s) * Commonly used TV Resolution = 720 x 576 (

) * Black levels = 0 mV or 0 IRE * White levels (

Chrominance Chrominance (''chroma'' or ''C'' for short) is the signal used in video systems to convey the color information of the picture (see YUV color model), separately from the accompanying Luma (video), luma signal (or Y' for short). Chrominance is usu ...

amplitude The amplitude of a periodic variable is a measure of its change in a single period (such as time or spatial period). The amplitude of a non-periodic signal is its magnitude compared with a reference value. There are various definitions of am ...

): ** 700 mV p-p or 100 IRE - 100% intensity setting which corresponds to 100.0.100.0

SMPTE color bars SMPTE color bars are a television test pattern used where the NTSC, NTSC video standard is utilized, including countries in North America. The Society of Motion Picture and Television Engineers (SMPTE) refers to the pattern as Engineering Guide ...

. ** 75% intensity corresponding to 100.0.75.0 color bars, also referred to as EBU Bars.

=Variants

Broadcast safe 525 video

Broadcast safe standards for 525 lines of

( System M,

NTSC NTSC (from National Television System Committee) is the first American standard for analog television, published and adopted in 1941. In 1961, it was assigned the designation System M. It is also known as EIA standard 170. In 1953, a second ...

NTSC-J NTSC-J or "System J" is the informal designation for the analogue television standard used in Japan. The system is based on the US NTSC ( NTSC-M) standard with minor differences. While NTSC-M is an official CCIR and FCCNational Television Sys ...

, PAL-M) video are: * Common name = 525/60i (

480i 480i is the video mode used for standard-definition digital video in the Caribbean, Japan, South Korea, Taiwan, Philippines, Myanmar, Western Sahara, and most of the Americas (with the exception of Argentina, Paraguay, and Uruguay). The ...

) * Commonly used digital SD SDI baseband signal =

, 270 Mbit/s bitrate * Commonly used Frame rate = 30 frame/s black and white, 29.97 interlaced frame/s color * Black level = 7.5 IRE for

, 0 IRE for

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

and PAL-M in

Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...

. * Blanking level = 0 IRE * White levels = 100 IRE, 714 mV * Maximum signal level = 120 IRE * Minimum signal level = -20 IRE

=Variants

Broadcast safe High Definition video

Digital broadcasting is very different from analog. The NTSC and PAL standards describe both transmission of the signal and how the electrical signal is converted into an image. In digital, there is a separation between the subject of how data is to be transmitted from tower to TV, and the subject of what content that data might contain. While data transmission is likely to be a fixed and consistent affair, the content could vary from High Definition video, to SD multicasting the next, and even to non-video datacasting. For ATSC 1.0, 8VSB transmits the data, while

MPEG-2 MPEG-2 (a.k.a. H.222/H.262 as was defined by the ITU) is a standard for "the generic coding of moving pictures and associated audio information". It describes a combination of lossy video compression and lossy audio data compression methods ...

encodes pictures and sound.

Broadcast safe audio

Broadcast engineers in

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

usually line up their audio gear to nominal reference level of 0 dB on a

VU meter A volume unit (VU) meter or standard volume indicator (SVI) is a device displaying a representation of the Signal-to-noise ratio, signal level in audio equipment. The original design was proposed in the 1940 Institute of Radio Engineers, IRE pap ...

aligned to +4 dBu or -20 dBFS, in

equating to roughly +4 dBm or -18 dBFS. Peak signal levels must not exceed the nominal level by more than +10 dB. Broadcast audio as a rule must be as free as possible of

Gaussian noise Carl Friedrich Gauss (1777–1855) is the eponym of all of the topics listed below. There are over 100 topics all named after this German mathematician and scientist, all in the fields of mathematics, physics, and astronomy. The English eponymo ...

, that is to say, it must be as far from the

noise floor In signal theory, the noise floor is the measure of the signal created from the sum of all the noise sources and unwanted signals within a measurement system, where noise is defined as any signal other than the one being monitored. In radio com ...

, as is reasonably possible considering the storage or transmission medium. Broadcast audio must have a good

signal-to-noise ratio Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to noise power, often expressed in deci ...

, where speech or music is a bare minimum of 16db above the noise of the recording or transmission system. For audio that has a much poorer signal-to-noise ratio (like

cockpit voice recorder A flight recorder is an electronic recording device placed in an aircraft for the purpose of facilitating the investigation of aviation accidents and incidents. The device may often be referred to colloquially as a "black box", an outdated nam ...

s), sonic enhancement is recommended.

Non-standard video

Although almost any video gear can create problems when broadcast, equipment aimed at consumers sometimes produces video signals which are not broadcast safe. Usually this is to reduce the cost of the gear, since a non-standard video signal in the home might not create the problems that one might find in a broadcast facility. Potential flaws exist with: * VHS and 8 mm: Consumer devices generally lack time base correction that may cause problems with

genlock Genlock (generator locking) is a common technique where the video output of one source (or a specific reference signal from a signal generator) is used to synchronize other picture sources together. The aim in video applications is to ensure the ...

and sync with some analogue and digital broadcast equipment. Consumer analogue video systems have greater system noise and lower chrominance and luminance than is normal for standard definition TV. As a general broadcast engineering rule all analogue videotape origin material should be genlocked before transmission, but this is not mandatory or necessary for all conditions. All analogue videotape by default is broadcast safe under normal playing conditions. * Older videogame systems: Video game consoles before the sixth generation and 8-bit

home computer Home computers were a class of microcomputers that entered the market in 1977 and became common during the 1980s. They were marketed to consumers as affordable and accessible computers that, for the first time, were intended for the use of a s ...

s generated a video signal lacking the half scan line needed to make interlace happen. This subtle simplification caused NTSC sets to scan 240p/60 instead of 480i60, with similar results for

. While this actually improved picture quality for the kind of low-definition images that videogames of this era generated, such a signal modification could cause problems in a broadcast environment as the signal behaviour is outside the original television system specifications. Genlocking—but not timebase correction—are the recommended broadcast engineering solutions. * Computer video signals: Computer video can be set up to run at many different frame or field rates, ranging 50 frame/s to more than 240 frame/s. Computer video is generally progressive by default, but many interlaced modes exist. A

scan converter Scan conversion or scan converting rate is a video processing technique for changing the vertical / horizontal scan frequency of video signal for different purposes and applications. The device which performs this conversion is called a scan con ...

is typically needed to convert these signals to one of the many acceptable broadcast standards, such as 59.94 Hz or 50 Hz. This type of conversion typically degrades the quality of the broadcast image, usually resulting with either "motion artifacts" or a lower resolution. It is recommended that the display rate be set to equal the target television rate if possible.

In digital television only environments

In nations that have fully converted to digital television, broadcast safe analogue television takes on a slightly different meaning. All broadcasting systems will have been mostly converted to digital only outputs, leaving fewer entry points for analogue television signals. What this means is that all devices that feed to the television transmitter must take in and feed standard analogue television signals into the transmission chain. Mostly it is up to the switcher to notify if there is non-broadcast safe video to the programmer. However, due to the limitations of many switchers for DTV and HDTV it ultimately is up to the automation systems to alert the programmer of non-broadcast safe video inputs. As a matter of broadcast engineering practice, 4:3 analogue television signals will always pose the most problems with broadcast safe compliance. The use of portable and cheap timebase-genlock systems for analogue television inputs in the digital television studio will be clearly mandatory for the next 50 years.

References

{{DEFAULTSORT:Broadcast-Safe Broadcast engineering ITU-R recommendations Television technology Television terminology

Broadcast safe video

Broadcast safe standard-definition video

Broadcast safe 625 video

=Variants

Broadcast safe 525 video

=Variants

Broadcast safe High Definition video

Broadcast safe audio

Non-standard video

In digital television only environments

See also

References