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Old April 9th, 2008, 03:57 AM   #1
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"Broadcast safe" - is it relevant if not broadcasting?

This may seem like an obvious question - but please indulge my 3 part question...

1. Was broadcast safe developed/designed for "older" CRT TVs, and perhaps don't apply across the board to most modern HDTVs in general? Is the answer the same if there is no Network broadcast involved?

2. If I'm shooting and editing for a closed circuit loop (no Network broadcast), and the TVs are HD LCDs/PLASMAs - do I need to worry about broadcast safe? What if some of these in-loop TVs were CRT?

3. If I'm only outputting to DVD - and I'm not sure about the end users TVs, should the DVD be filtered for "broadcast safe"?

Thanks in advance,
Lonnie
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Old April 9th, 2008, 09:14 AM   #2
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Broadcast safe is a term that goes hand in hand with the often misused 'broadcast quality'.

Broadcast safe means that all colors within the video fall within the legal gamut of NTSC transmission standards. In short, if it's not going to be aired or sent through cable/sat, then it doesn't really apply to your stuff.

Broadcast quality also means video/audio that falls within the technical limits for broadcast. It has nothing to do with shooting on a small handycam vs. a large shoulder mounted ENG camera. Picture quality does not apply. Cellphone video can be broadcast quality if it is encoded with luminance, chrominance, timing, sync levels, etc. that are okay to send over the air.

-gb-
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Old April 9th, 2008, 10:53 AM   #3
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Thanks Greg - I met you at the Sony booth on one of your seminars on the XDCAM at NAB '07... Peoples of the forum - Greg Boston is a nice guy!

I had a feeling that it was transmission requirements, but also on a practical note: NTSC and the upcoming ATSC are two different beasts all together, so... (this should probably go in a different thread, but...)

1. Should we look for a change to Broadcast Safe filters or requirements when we switch over to the all digital mandate and ATSC?

2. I'm aware our TVs and DVD players with upscalers will be able to play our "legacy" DVDs with NTSC standards after the mandated switch to ATSC... But, DVD players, burners, and discs that use to be NTSC - will they be going to ATSC standards as well? or is this incarnate Blu Ray - or something else we haven't seen yet?

Thanks,
Lonnie
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Old April 9th, 2008, 12:21 PM   #4
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Thanks for the kind words. You obviously saw me after my morning coffee.

Seriously though, you have to look at the SMPTE standards for HD colorspace to get the answers you want.

I'm guessing we won't see DVD boxes with ATSC output because everything can be done with alternate connections these days (HDMI, Component, 1394).

I remember meeting you at NAB last year. Hope to see you again this year.

regards,

-gb-
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Old April 9th, 2008, 12:56 PM   #5
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If you're making DVDs, you should try to make sure you aren't sending really illegal levels to the TV. Older sets can misinterpret superblacks as sync and this will cause a rolling picture. I think most NLEs will have difficulty doing this except for Vegas. In Vegas, depending on what levels you are working with (do this only if the codec expects studio RGB levels), you may need to use a solid color generator of 16 16 16 RGB on the bottommost track to avoid this.

You might also have problems with other illegal colors... it would be generally safe to add a broadcast safe filter with very lenient settings (e.g. composite IRE max of 133). Broadcast is much more restrictive than this.
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Old April 9th, 2008, 12:59 PM   #6
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Quote:
2. If I'm shooting and editing for a closed circuit loop (no Network broadcast), and the TVs are HD LCDs/PLASMAs - do I need to worry about broadcast safe?
In that particular case could you do a test? Then you know for sure whether or not it's needed. Probably your most gains would be making sure their loop is setup correctly, with no ground loops or ghosting or anything like that (in other words, does the final picture look right?). It's unlikely that you'd have too much problems with illegal levels.
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Old April 9th, 2008, 01:11 PM   #7
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Glenn & Greg - many thanks to you both...

Quick Qs...

Does IRE max of 133 only pertain to the whites or is that the magic cap for all of the light in the shot combined?

(and yes, if I could or can test in advance, I always will.)

Thanks again,
Lonnie
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Old April 10th, 2008, 01:33 AM   #8
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The composite signal is a composite of two things:
The luma signal
The chroma signal

For the luma signal, the legal range is 7.5 IRE for NTSC countries except Japan, 0-100 IRE for PAL countries and Japan.

Can't remember the limit of the chroma signal.

Anyways the two signals get modulated/combined together when it gets sent down a single wire. That's the composite signal. It has a range of what works and what doesn't; this range is smaller for broadcast. The limit is 133 IRE on the high end, and for broadcast it's lower than that (though it depends on broadcaster). On the low end the limit is like -20 IRE.
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Old April 10th, 2008, 01:09 PM   #9
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Quote:
Originally Posted by Glenn Chan View Post
The composite signal is a composite of two things:
The luma signal
The chroma signal

For the luma signal, the legal range is 7.5 IRE for NTSC countries except Japan, 0-100 IRE for PAL countries and Japan.

Can't remember the limit of the chroma signal.

Anyways the two signals get modulated/combined together when it gets sent down a single wire. That's the composite signal. It has a range of what works and what doesn't; this range is smaller for broadcast. The limit is 133 IRE on the high end, and for broadcast it's lower than that (though it depends on broadcaster). On the low end the limit is like -20 IRE.
The broadcaster will want you to keep the top at or below 100IRE. 110 is the absolute maximum level they can transmit before overmod occurs on the AM video portion. In the modulation of the transmitter, white is the minimum point of the wave while black is the maximum point. Therefore, white level cannot be less than 10%, otherwise it might reach zero. When that happens, you create spurious emissions on radio frequencies other than your assigned frequency and that's what gets you into trouble with the FCC. 7.5 IRE is used as the minimum to prevent black portions of the video signal getting too high such that they interfere with the sync pulses.

-gb-
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Old April 11th, 2008, 01:57 PM   #10
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110 is the absolute maximum level they can transmit before overmod occurs on the AM video portion.
That's for the luma and not composite right?
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