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Headswitching

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Maria Luisa Gambale
Headswitching
on Mar 12, 2011 at 5:41:24 pm

We are about to go to master tape for our hour-long documentary which incorporates a number of different footage sources. We have already converted all of our non-23.98fps footage to our 23.98 ProRes timeline and color corrected; but we are just realizing that in our Quicktime movie there is a small amount of headswitching visible in footage that was shot HDV Pal 25fps. We did not notice this after the conversion at the quality control session.

We are prepared to blow this up 2-3% if necessary, but it's not ideal since this footage is HDV. We are wondering if it's possible that this is an underscanning issue: that we are seeing a part of the frame that no one will see through any form of projection or broadcast. Does anyone have any experience with this issue? Do you know if broadcasters will reject footage with this problem?

Many thanks.

Maria Luisa Gambale
DP/Producer
Brooklyn, NY


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Chad Brewer
Re: Headswitching
on Mar 13, 2011 at 12:47:46 am

Head switching was sometimes visible in old analog recording like VHS and U-Matic. Whatever you're seeing is not head switching as you say it's only on footage from 25fps HDV (PAL refers to SD).

It is possible that whatever you're seeing will not be displayed in correctly broadcasted/projected overscan situations, but I don't know exactly what you're seeing.

It's possible that these HDV clips have not been converted or scaled correctly to the rest of your project which I'm assuming is not HDV frame size.

Have you had the chance to view what you're seeing as problematic on a broadcast monitor yet? If not, what program are you viewing this through that is creating the worry? - that could make a difference as different software viewers have different aperture settings. It's most likely something that will not come through in proper scan, but I can't say for sure. Posting a screen shot of what you are seeing would be most helpful.

Chad Brewer
Senior Broadcast Videotape Operator
TeleVersions, LLC


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Rafael Amador
Re: Headswitching
on Mar 13, 2011 at 2:02:18 am

I agree with Chad; have a look again to that footage.
HDV should perfectly fit the HD frame.
rafael

http://www.nagavideo.com


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Maria Luisa Gambale
Re: Headswitching
on Mar 13, 2011 at 3:21:26 pm

I've attached the image. Apologies for the terminology confusion; our Executive Producer threw the name in the ring, and we all just adopted it.

Updated information:

The footage is actually old DV material, still PAL. We are working in a 1920x1080 timeline.

It seems like these problem parts of the 1920x1080 image would show in projection and on HD flatscreen TV's.

So, some people here in NYC have actually recommended that we crop the whole movie. Our editor is trying 0.5 crop in FCP for the bottom and 0.2 for the top. But we want to confirm that this is an acceptable fix for broadcast and for theatrical projection. Otherwise, we'd have to blow up just those shots (DV, approx. 5-6 minutes in a 57-minute movie) 2-3%.

I've attached an image, but it's really hard to tell from a still image. At the bottom of the image, you can see the width of the stripe in the white wall where the bad part is slightly brighter. It's also happening on the top, and you can tell at the right of her head scarf.



Thank you all for your advice so far!

Maria Luisa Gambale
DP/Producer
Brooklyn, NY


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Bob Zelin
Re: Headswitching
on Mar 13, 2011 at 9:01:34 pm

I am so happy that you posted this, because now I have
an opportunity to yell at you, and your company.

Guess what - you have technical problems. Guess what, you live
in NYC, where there are COUNTLESS qualified video engineers, countless
qualified professional post houses, and countless places to buy or rent
a waveform monitor for you to analyze what is going on.

Guess what - YOU HAVE TO HIRE SOMEONE, or BUY SOMETHING, or RENT SOMETHING
to figure out what is going on. Your crap at the bottom of the screen can be
anything - "head switching noise" (which was prevalent from older VTR's with TBC's in them),
or blanking errors, or something else. Even I could not diagnose what is going on
unless I saw it on a waveform monitor to see if it was legal.

This is exactly what broadcasting is about, and this is exactly what standards are about
and using professional people with professional equipment is about.

Will your stuff get rejected - ABSOLUTELY. Do you need to figure out what is going on -
ABSOLUTELY. This is done by all of what I have mentioned before -

1) Hire a freelancer that knows broadcast spec, or a freelance engineer
2) Rent or buy a waveform monitor (no, not the one built into FCP or your AVID)
3) go to one of the 1000 post houses in NY that have the staff and equipment that can
analyze this for you.

I used to hate all these standards, but I now realize, that this is what keeps hi end places
in business.

Bob Zelin



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Chad Brewer
Re: Headswitching
on Mar 14, 2011 at 12:41:08 am

Maria,
Bob is also from NYC, if you couldn't tell, and now you've both met on the COW.

It is very true that certain portions of all images should be under the view of a professional scope. In your case, I would not crop the entire film, only minimally crop the PAL DV shots to eliminate what appears to be how interlaced lines drawn in DV are "exposed" when uprezed to 1080. Nothing will be rejected by such a slight cropping before mastering to tape

When you master to tape however, it will be up to the mastering house to make sure that your entire program is in spec based on scope measurements and other tape layout procedures when it goes to a professional VTR based on the requirements set by whomever will be receiving the program.

Bob's suggestions have credence.
Hopefully this helps as well.

Chad Brewer
Senior Broadcast Videotape Operator
TeleVersions, LLC


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Bob Zelin
Re: Headswitching
on Mar 14, 2011 at 9:17:53 pm

answer me this Chad,
how do you create a show for broadcast delivery with -
1) no test equipment
2) no professional trained personel
3) no willingness to go to a "mastering" house or professional post production house"
4) no willingness to rent the proper equipment to accomplish this

tell me Chad - how do you make a broadcast show, without hiring the correct staff or equipment ? How do you do it with untrained unqualified personel, or without the right equipment ? Or the unwillingness to to out of house, to have it done for you ?
Tell me Chad - how can the owner of this company keep all the profits for himself, without spending one penny to accomplish this ?

bob Zelin



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Sam Cole
Re: Headswitching
on Mar 14, 2011 at 11:35:10 pm

Bob - we deal with these types all the time. It is a real education to them when they see what we go thru to 'legalise' their product before it goes to tape.
And then we send them the bill and they SCREAM!!!

But creatives are just that and to edit a show without concern for the technicals is a weight off their shoulders and more money for my company.

Sam Cole
On line Mastering Facility
FCP, Avid, Adobe
Sydney, Australia


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Chad Brewer
Re: Headswitching
on Mar 15, 2011 at 12:14:00 am

[Bob Zelin] "tell me Chad - how do you make a broadcast show, without hiring the correct staff or equipment ?"

Bob,
In my last post I mentioned going to a mastering house, did I not? Where did I come off saying professional equipment and professionals who know how to use the equipment are not necessary? One is EXTREMELY challenged and/or doomed for rejection in meeting broadcast specs without them. That's one of the reasons companies like TeleVersions are still in business. Being one of, if not the Midwest's highest-end broadcast/mastering facilities with all the necessary equipment, I'm so used to people in situations like this coming to a dedicated facility like ours to ensure their mastering is to whatever broadcast spec must be met.

In offering my advice on the original post, I guess I was assuming they were prepping this to take to a mastering house. In no way was I insinuating that mastering for broadcast can be achieved without the proper equipment and personnel. If I was, the company I work for would be out of business and I would be unemployed.

I don't know why your post was directed towards me (instead of cheapskates out there who think they can do it all themselves without professionals like us). Why would I invalidate what I do every day to make a living?

Chad Brewer
Senior Broadcast Videotape Operator
TeleVersions, LLC


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Maria Luisa Gambale
Re: Headswitching
on Mar 15, 2011 at 12:23:36 am

This chain of messages is very funny. Just to clear up a few wrong assumptions (though I hate to break anyone's stride here), we are taking it to a post house for mastering. They hardware-converted the offending footage for us originally and didn't catch the problem. We discovered the issue over the weekend with a tape mastering session planned at the post house for Monday morning. Not being able to reach them, we were trying to figure out some possible answers over the weekend from anyone who was available, so that we could show up prepared with options, as our film is due to be sent to an international festival tomorrow.

I did manage to consult off the forum with some editors and post-production professionals, and we got our answers. Notably not here.

Maria Luisa Gambale
DP/Producer
Brooklyn, NY


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Chad Brewer
Re: Headswitching
on Mar 15, 2011 at 1:02:23 am

[Maria Luisa Gambale] "Notably not here."

Ouch.

Maria, I hope you know I was only trying to help based on experience and something I could not see for myself.

Regardless, I'm glad you got things fixed for your film.
Best wishes for the festival as well!

Chad Brewer
Senior Broadcast Videotape Operator
TeleVersions, LLC


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Bob Zelin
Re: Headswitching
on Mar 16, 2011 at 7:38:37 pm

Chad,
are you hypersensitive, or what ? Where did you ever get the impression that I was refering to you, anywhere in my respone here ?
I only support what you said, never saying anything negative about your comments.

Bob Zelin



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Chad Brewer
Re: Headswitching
on Mar 17, 2011 at 12:15:35 am

[Bob Zelin] "I only support what you said, never saying anything negative about your comments."

Thanks Bob. I misinterpreted what you wrote. I know we're pretty much on the same page when it comes to what it takes to produce broadcast quality material and specs...

It's funny now looking back on the original post. My first reply was that the HDV material in question was probably not converted correctly. Later, the original poster found out and reported that the HDV material was not hardware converted correctly and that the answers to the problem were "most notably" not found here on the COW. I guess some people just don't like FREE advice...

Chad Brewer
Senior Broadcast Videotape Operator
TeleVersions, LLC


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Maria Luisa Gambale
Re: Headswitching
on Mar 17, 2011 at 12:54:31 am

No, you tried to be helpful, Chad, and I do appreciate that. It's just the meaningless tirades that came after that sullied the experience. Forums and chatrooms are popular homes for people who have a found a place to project their negativity or bitterness, but it's still always a bit of a shock to find out that people have time for it. It's harder to construct a response with intelligence and civility, but it would be a worthwhile exercise for some people here (yourself not included).

Maria Luisa Gambale
DP/Producer
Brooklyn, NY


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Tom Matthies
Re: Headswitching
on Mar 18, 2011 at 8:07:34 pm

Bob, sometimes your posts are less than helpful.
No more coffee for you!

E=MC2+/-2db


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Sam Cole
Re: Headswitching
on Mar 19, 2011 at 3:02:26 am

In a world where less and less people care about the 'technical' side of television I can understand Bob's feelings. Its like his career is slipping away.
I remember the days when we use to put Bars and Tone at the front of every tape. Nowdays we get tapes from television networks with audio levels thru the roof, no bars and tone, incorrect or no VITC, timecode disruptions and channel errors.
These things would be instant rejects if we sent the networks tapes with similar problems.

Sam Cole
On line Mastering Facility
FCP, Avid, Adobe
Sydney, Australia


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Tom Matthies
Re: Headswitching
on Mar 29, 2011 at 6:44:47 pm

I agree. I still use my trusty old Tektronix 1740/760 combo. I also have a Magni SDM-560M SDI analyzer that all my standard definition video takes a trip through to make sure that everything is as it should be before sending it out.
Why do I still do this? I'm not all that sure anymore since no one seems to care about technical issues these days.
Tom

E=MC2+/-2db


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