Broadcast-safe
Encyclopedia
Broadcast-safe video is a term used in the broadcast
industry to define video
and audio
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 Federal Communications Commission
(FCC) is the regulatory authority; in most of Europe, standards are set by the European Broadcasting Union
(EBU).
, a colour encoding that is usually used with such systems) video
are :
) video are :
transmits the data, while MPEG-2
encodes pictures and sound.
usually line up their audio gear to nominal reference level of 0 dB on a VU meter
aligned to +4dBu or -20dBFs, in Europe
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
, that is to say, it must be as close to the noise floor
, as is reasonably possible, considering the storage or transmission medium.
Broadcast audio must have a good signal-to-noise ratio
, 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
s), sonic enhancement is recommended.
Potential flaws exist with:
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.
Broadcast
Broadcast or Broadcasting may refer to:* Broadcasting, the transmission of audio and video signals* Broadcast, an individual television program or radio program* Broadcast , an English electronic music band...
industry to define video
Video
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
and audio
Content (media and publishing)
In media production and publishing, content is information and experiences that may provide value for an end-user/audience in specific contexts. Content may be delivered via any medium such as the internet, television, and audio CDs, as well as live events such as conferences and stage performances...
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 Federal Communications Commission
Federal Communications Commission
The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the...
(FCC) is the regulatory authority; in most of Europe, standards are set by the European Broadcasting Union
European Broadcasting Union
The European Broadcasting Union is a confederation of 74 broadcasting organisations from 56 countries, and 49 associate broadcasters from a further 25...
(EBU).
Broadcast safe 625 video
Broadcast safe standards for 625 lines of Standard Definition (Inaccurately referred to as PALPAL
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...
, a colour encoding that is usually used with such systems) video
Video
Video is the technology of electronically capturing, recording, processing, storing, transmitting, and reconstructing a sequence of still images representing scenes in motion.- History :...
are :
- Common name = 625/50i (576i576i576i is a standard-definition video mode used in PAL and SECAM countries. In digital applications it is usually referred to as "576i", in analogue contexts it is often quoted as "625 lines"...
) - Commonly used digital SDStandard-definition televisionSorete-definition television is a television system that uses a resolution that is not considered to be either enhanced-definition television or high-definition television . The term is usually used in reference to digital television, in particular when broadcasting at the same resolution as...
SDISerial Digital InterfaceSerial digital interface is a family of video interfaces standardized by SMPTE. For example, ITU-R BT.656 and SMPTE 259M define digital video interfaces used for broadcast-grade video...
baseband signal = SMPTE 259M-C, 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 (576i576i576i is a standard-definition video mode used in PAL and SECAM countries. In digital applications it is usually referred to as "576i", in analogue contexts it is often quoted as "625 lines"...
) - Black levels = 0 mVVoltThe volt is the SI derived unit for electric potential, electric potential difference, and electromotive force. The volt is named in honor of the Italian physicist Alessandro Volta , who invented the voltaic pile, possibly the first chemical battery.- Definition :A single volt is defined as the...
or 0 IREIRE (unit)An IRE is a unit used in the measurement of composite video signals. Its name is derived from the initials of the Institute of Radio Engineers.... - White levels (ChrominanceChrominanceChrominance is the signal used in video systems to convey the color information of the picture, separately from the accompanying luma signal . Chrominance is usually represented as two color-difference components: U = B' − Y' and V = R' − Y'...
amplitudeAmplitudeAmplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
):- 700 mV p-pAmplitudeAmplitude is the magnitude of change in the oscillating variable with each oscillation within an oscillating system. For example, sound waves in air are oscillations in atmospheric pressure and their amplitudes are proportional to the change in pressure during one oscillation...
or 100 IRE - 100% intensity setting which corresponds to 100.0.100.0 color bars. - 75% intensity corresponding to 100.0.75.0 color bars, also referred to as EBU Bars.
- 700 mV p-p
Variants
| Resolution | Aspect ratio | Pixel aspect ratio Pixel aspect ratio Pixel aspect ratio is a mathematical ratio that describes how the width of a pixel in a digital image compares to the height of that pixel.... |
Form of scanning | Framerate (Hz Hertz The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications.... ) |
|
|---|---|---|---|---|---|
| Vertical | Horizontal | ||||
| 576 | 352 | 4:3 or 16:9 | non-square | interlaced | 25 (50 fields/s) |
| progressive | 25 | ||||
| 480 | 4:3 or 16:9 | non-square | interlaced | 25 (50 fields/s) | |
| progressive | 25 | ||||
| 544 | 4:3 or 16:9 | non-square | interlaced | 25 (50 fields/s) | |
| progressive | 25 | ||||
| 720 | 4:3 or 16:9 | non-square | interlaced | 25 (50 fields/s) | |
| progressive | 25 50 |
||||
Broadcast safe 525 video
Broadcast safe standards for 525 lines of Standard Definition (System M, NTSCNTSC
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...
) video are :
- Common name = 525/60i (480i480i480i is the shorthand name for a video mode, namely the US NTSC television system or digital television systems with the same characteristics. The i, which is sometimes uppercase, stands for interlaced, the 480 for a vertical frame resolution of 480 lines containing picture information; while NTSC...
) - Commonly used digital SDStandard-definition televisionSorete-definition television is a television system that uses a resolution that is not considered to be either enhanced-definition television or high-definition television . The term is usually used in reference to digital television, in particular when broadcasting at the same resolution as...
SDISerial Digital InterfaceSerial digital interface is a family of video interfaces standardized by SMPTE. For example, ITU-R BT.656 and SMPTE 259M define digital video interfaces used for broadcast-grade video...
baseband signal = SMPTE 259M-C, 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 NTSCNTSCNTSC, 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...
in the USUnited StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
, 0 IRE in JapanJapanJapan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
. - Blanking level = 0 IRE
- White levels = 100 IRE, 714 mV
- Maximum signal level = 120 IRE
- Minimum signal level = -20 IRE
Variants
| Resolution | Aspect ratio | Pixel aspect ratio Pixel aspect ratio Pixel aspect ratio is a mathematical ratio that describes how the width of a pixel in a digital image compares to the height of that pixel.... |
Form of scanning | Framerate (Hz Hertz The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications.... ) |
|
|---|---|---|---|---|---|
| Vertical | Horizontal | ||||
| 480 | 640 | 4:3 | square | interlaced | 29.97 (59.94 fields/s) 30 (60 fields/s) |
| progressive | 23.976 24 29.97 30 59.94 60 |
||||
| 720 | 4:3 or 16:9 | non-square | interlaced | 29.97 (59.94 fields/s) 30 (60 fields/s) |
|
| progressive | 23.976 24 29.97 30 59.94 60 |
||||
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 one hour, to SD multicasting the next, and even to non-video datacasting. In the US, 8VSB8VSB
8VSB is the modulation method used for broadcast in the ATSC digital television standard. ATSC and 8VSB modulation is used primarily in North America; in contrast, the DVB-T standard uses COFDM....
transmits the data, while MPEG-2
MPEG-2
MPEG-2 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 which permit storage and transmission of movies using currently available storage media and transmission...
encodes pictures and sound.
| Resolution | Aspect ratio | Pixel aspect ratio Pixel aspect ratio Pixel aspect ratio is a mathematical ratio that describes how the width of a pixel in a digital image compares to the height of that pixel.... |
Form of scanning | Framerate (Hz Hertz The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications.... ) |
|
|---|---|---|---|---|---|
| Vertical | Horizontal | ||||
| 720 | 1280 | 16:9 | square | progressive | 23.976 24 25 29.97 30 50 59.94 60 |
| 1080 | 1920 | 16:9 | square | interlaced | 25 (50 fields/s) 29.97 (59.94 fields/s) 30 (60 fields/s) |
| progressive | 23.976 24 25 29.97 30 |
||||
Broadcast safe audio
Broadcast engineers in North AmericaNorth America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
usually line up their audio gear to nominal reference level of 0 dB on a VU meter
VU meter
A VU meter is often included in audio equipment to display a signal level in Volume Units; the device is sometimes also called volume indicator ....
aligned to +4dBu or -20dBFs, in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
equating to roughly +4 dBm or -18 dBFS
DBFS
Decibels relative to full scale, commonly abbreviated dBFS, measures decibel amplitude levels in digital systems such as pulse-code modulation which have a defined maximum available peak level....
. 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
Gaussian noise
Gaussian noise is statistical noise that has its probability density function equal to that of the normal distribution, which is also known as the Gaussian distribution. In other words, the values that the noise can take on are Gaussian-distributed. A special case is white Gaussian noise, in which...
, that is to say, it must be as close to the noise floor
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 the noise is defined as any signal other than the one being monitored....
, as is reasonably possible, considering the storage or transmission medium.
Broadcast audio must have a good signal-to-noise ratio
Signal-to-noise ratio
Signal-to-noise ratio is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. It is defined as the ratio of signal power to the noise power. A ratio higher than 1:1 indicates more signal than noise...
, 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
Cockpit voice recorder
A cockpit voice recorder , often referred to as a "black box", is a flight recorder used to record the audio environment in the flight deck of an aircraft for the purpose of investigation of accidents and incidents...
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 genlockGenlockGenlock 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 television picture sources together. The aim in video and digital audio applications is to ensure the coincidence of signals in time at a...
and sync with some analogue and digital broadcast equipment. Consumer analogue video systems have greater system noise and lower chrominance and luminace 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 : Before the sixth generationHistory of video game consoles (sixth generation)The sixth-generation era refers to the computer and video games, video game consoles, and video game handhelds available at the turn of the 21st century. Platforms of the sixth generation include the Sega Dreamcast, Sony PlayStation 2, Nintendo GameCube, and Microsoft Xbox...
of videogame consoles, most videogames 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 480i/60, with similar results for PALPALPAL, 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...
. While this actually improved picture quality for the kind of 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 "Scanrate Converter" is typically needed to convert these signals to one the many acceptable broadcast standards, such as 59.97 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.
See also
- 576i576i576i is a standard-definition video mode used in PAL and SECAM countries. In digital applications it is usually referred to as "576i", in analogue contexts it is often quoted as "625 lines"...
- 480i480i480i is the shorthand name for a video mode, namely the US NTSC television system or digital television systems with the same characteristics. The i, which is sometimes uppercase, stands for interlaced, the 480 for a vertical frame resolution of 480 lines containing picture information; while NTSC...
- VU meterVU meterA VU meter is often included in audio equipment to display a signal level in Volume Units; the device is sometimes also called volume indicator ....
- Peak programme meterPeak programme meterA peak programme meter is an instrument used in professional audio for indicating the level of an audio signal.There are many different kinds of PPM. They fall into broad categories:...
- SMPTE color barsSMPTE color barsThe SMPTE color bars are a type of television test pattern, and is most commonly used in countries where the NTSC video standard is dominant, such as those in North America. The Society of Motion Picture and Television Engineers refers to this test pattern as Engineering Guideline EG 1-1990...
- ProcAmp
- Safe areaSafe areaSafe area is a term used in television production to describe the areas of the television picture that can be seen on television screens.Older televisions can display less of the space outside of the safe area than ones made more recently...