Broadcast safe
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Broadcast safe or broadcast legal 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 [1]. 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).
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[edit] Broadcast safe video
[edit] Broadcast safe Standard Definition video
[edit] 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) video are [2] [3]:
- 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 (576i)
- Black levels = 0 mV or 0 IRE
- White levels (Chrominance amplitude):
- 700 mV p-p 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 .
[edit] Broadcast safe 525 video
Broadcast safe standards for 525 lines of Standard Definition (NTSC) video are [4] [5] [6] [7] [8]:
- Commonly used Frame rate = 30 frame/s black and white, 29.97 frame/s color
- Black level = 7.5 IRE for NTSC in 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
[edit] Non-Standard Video
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-band versions transmit noticeably less detail and more noise then 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 interlace happen. 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.
[edit] 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, 8VSB transmits the data, while MPEG-2 encodes pictures and sound.
| Resolution | Aspect ratio | Pixel aspect ratio | Form of scanning | Framerate (Hz) | |
|---|---|---|---|---|---|
| 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 |
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[edit] Broadcast safe audio
Broadcast engineers in North America usually line up their audio gear to 0 db using a VU meter, in Europe equating to roughly +4 dB ~ +6 dB on a PPM [9] .
[edit] See also
[edit] External links
[edit] References
- ^ After Effects CS3 - Broadcast-safe colors
- ^ Matrox - Composite video measurements
- ^ VideoUniversity.com - PAL Colour Bars
- ^ VideoUniversity.com - Engineering Primer
- ^ Tektronix - The Color Bars Signal -- Why and How
- ^ The 7.5 IRE Setup Problem
- ^ GeniusDV - Adobe Photoshop and NTSC Color Safe
- ^ VideoUniversity.com - Broadcast Requirements for Commercials and Informercials
- ^ Shure - VU and PPM Audio Meters: An Elementary Explanation
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