Broadcast-safe or broadcast legal or legal signal is a term used in the
broadcastindustry to define videoand audiocompliant with the technicalor regulatory broadcast requirements of the target area or region the feed might be broadcasting to [ [http://livedocs.adobe.com/en_US/AfterEffects/8.0/help.html?content=WSE0A9B424-9673-4fd0-BED7-2ED4E1EB1E8D.html After Effects CS3 - Broadcast-safe colors] ] . 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).
Broadcast safe video
Broadcast safe Standard Definition video
Broadcast safe 625 video
Broadcast safe standards for 625 lines of
Standard Definition(Inaccurately referred to as PAL, a colour encoding that is usually used with such systems) videoare [ [http://www.matrox.com/video/support/ds/specs/ds_video/composite_video_measurements.cfm Matrox - Composite video measurements] ] [ [http://www.videouniversity.com/palbars.htm VideoUniversity.com - PAL Colour Bars] ] :
* Commonly used No. of Vertical Lines = 625 (576 visible active video)
* Commonly used Frame rate = 25 Hz (25 frame/s)
* Commonly used TV Resolution = 720 x 576 (
* Black levels = 0 mV or 0 IRE
* White levels (
** 700 mV p-p or 100 IRE - 100% intensity setting which corresponds to 188.8.131.52
** 75% intensity corresponding to 184.108.40.206 color bars, also referred to as EBU Bars .
Broadcast safe 525 video
Broadcast safe standards for 525 lines of
Standard Definition( NTSC) video are [ [http://www.videouniversity.com/engineer.htm VideoUniversity.com - Engineering Primer] ] [ [http://www.tek.com/Measurement/App_Notes/NTSC_Video_Msmt/colorbars.html?view=print&page=http://www.tek.com/Measurement/App_Notes/NTSC_Video_Msmt/colorbars.html Tektronix - The Color Bars Signal -- Why and How] ] [ [http://www.glennchan.info/articles/technical/setup/75IREsetup.html The 7.5 IRE Setup Problem] ] [ [http://www.geniusdv.com/weblog/archives/adobe_photoshop_and_ntsc_color_safe.php GeniusDV - Adobe Photoshop and NTSC Color Safe] ] [ [http://www.videouniversity.com/bcstreq.htm VideoUniversity.com - Broadcast Requirements for Commercials and Informercials] ] :
* Commonly used Frame rate = 30 frame/s black and white, 29.97 frame/s color
* Black level = 7.5 IRE for
NTSCin the US, 0 IRE in Japan.
* Blanking level = 0 IRE
* White levels = 100 IRE, 714 mV
* Maximum signal level = 120 IRE
* Minimum signal level = -20 IRE
Video gear aimed at consumers sometimes produces video signals which are not broadcast safe. Usually this is to reduce the cost of the gear, and because a non-standard video signal in the home might not create the problems that one might find in a broadcast facility. Some potential flaws:
* VHS and 8 mm: These formats are prone to
time base error, and in their non high-bandversions transmit noticeably less detail and more noise than is normal for standard definition TV.
* Older videogame systems: Before the sixth generation of videogame consoles, most videogames generated a video signal lacking the half scan line needed to make
interlacehappen. This subtle simplification caused NTSC sets to scan 240p instead of 480i, with similar results for PAL. While this actually improved picture quality for the kind of images that videogames of this era generated, such a signal would cause problems in a broadcast environment.
* VGA to NTSC converters: VGA runs at true 60 frame/s, not the slightly slower rate of NTSC. Some low cost VGA to NTSC converters could not correct for this, and would generate an NTSC signal with accelerated timing. Most TVs had no problem displaying this, but such a signal would rapidly deteriorate if recorded onto analog VCRs that are unable to compensate for the increased framerate.
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,
8VSBtransmits the data, while MPEG-2encodes pictures and sound.
Broadcast safe audio
Broadcast engineers in
North Americausually line up their audio gear to 0 db (-4.0 ~ 0.1 db) using a VU meter, in Europeequating to roughly +4 dB ~ +6 dB on a PPM [ [http://www.shure.com/ProAudio/Products/us_pro_ea_vu Shure - VU and PPM Audio Meters: An Elementary Explanation] ] .
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 recorders), sonic enhancement is recommended.
Peak programme meter
SMPTE color bars
* [http://www.ee.surrey.ac.uk/Contrib/WorldTV/broadcast.html More information about TV standards]
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