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720×486 versus 720×480
So I have a bit of a conundrum.
I work for a small cable tv show, and have been supervising our post production for a few weeks ever since our old production head quit. He had us running on an antiquated system, capturing off of DVCAM tapes to an uncompressed Cinewave format on old G5 towers in SD (and a G4), and then mastering back to DVCAM for broadcast.
Anyways, our Cinewave system and these towers have been buggy as all hell, and each edit bay he set up was incompatible for various reasons with every other edit bay we have.
The owners of the company have since promised a complete equipment upgrade for us once Apple releases towers with the hexacore processor (hopefully that day will come soon), but in the mean time we are stuck with what we’ve got. The other editors and I have been mulling over the possibility of just editing everything in DV, since we start on DVCAM tapes and end on DVCAM tapes, and the uncompressed Cinewave codec takes up a ton of space. We feel it would also help with our compatibility issues, since most of us personally own Intel Macbook Pros which we could edit segments of the show on.
While going through this process, we’ve run across the issue of the NTSC standard of 720×486 versus the DV standard of 720×480. For broadcast we’ve always sent our show out at 486 since we were told the extra six lines of resolution were utilized for closed captioning. So here are my questions…
1. What would be the simplest way to capture and edit in DV, while maintaining our 720×486 requirement for broadcast?
2. Is it true that those six lines of res are used for closed captioning?
3. Are they used for other anything else?
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9 Replies
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Lucas, there is really no reason in hell to convert DV to uncompressed. Some possible reasons are if you are doing a lot of compositing, CC work, green screen. But even then I don’t think it is worth the hassle, the storage space, the extra render times….
What do you deliver on? What kind of show is it? Cuts only? Heavy graphics? That is a big factor in figuring out your best workflow.
Scott Davis
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We master episodes onto DVCAM tapes and send them out for broadcast.
Yeah, the fact that our old production head had us doing everything uncompressed is pretty ridiculous. The only thing that’s holding us up from going completely DV is the 720×486 vs 720×480 resolution question. We want to make certain that we are giving the broadcast stations the resolution they need. That’s our big question.
-Tucker
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If you are laying back to DVCAM then you are delivering 720×480. DV is by definition 720×480 not 486. Beta, D-Beta are 486. The uncompressed 720×486 is a completely absurd middle step. Shoot DV, capture DV, output DV. Simple, cheap, easy. Don’t make it unnecessarily complicated.
Scott Davis
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Wasn’t looking for personal insults Dave. Was just looking for answers, and thanks for the ones you have given. Obviously, not all of us are masters of our domain. Never be afraid of asking stupid questions is my mantra.
We are doing a complete system overhaul, not just the Macs. I merely meant we are waiting for the new towers to be released before we do the entire overhaul.
This has been very illuminating. Thank you. Anyone else want to pile on?
-Tucker
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If you are going to post on the cow, you’ll need to get use to dave’s sarcastic and sometimes aggressively positioned responses. I’ve gotten used to them!
I fought with the same issue of 480 and 486. I still don’t fully understand it…thank god I’m with a company and fully in HD now!
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Ha ha ha. Will do Jason. Thanks!
-Tucker
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[Jason Brown] “I fought with the same issue of 480 and 486. I still don’t fully understand it.”
Both sizes when played back, gets converted in the same standard 525 lines NTSC analog signal.
For digital broadcast, I think that the standard is only 720×480 (MPEG-2, H264).
rafael -
[Dave LaRonde] “[Tucker Lucas] “Is it true that those six lines of res are used for closed captioning? ”
No. Closed captioning information is found in the scan lines of a TV signal that aren’t even a part of the picture, in Line 21. You have been misinformed. I also find this to be an EXTREMELY illuminating question about your level of knowledge, and your company’s level of knowledge.”
Hi Dave,
Actually, Tucker’s understanding is correct.The extra six lines (well, two of the six) are in fact used for SD closed captioning as the OP stated. Virtually all NLE systems (including all of the video cards that work with FCP) will map one of these 6 lines to VBI line 21 on capture and playback. This is the basis of how NLE closed captioning has been possible for the past several years (the technology was pioneered by CPC and eliminated the need for old linear deck-to-deck captioning hardware). For a visual explanation, please see: 720×486 NLE closed captioning.
Since DV is 720×480 and lacks the extra 6 lines, it doesn’t contain a line 21 as part of the picture data, but DV video does store closed captioning in a separate data area called DV VAUX. So if you are working with DV video over firewire and need closed captioning, it can be done: DV VAUX closed captioning.
I hope you find this information useful.
Jason Livingston
CPC Closed Captioning -
Both, Dave and you are right.
Dave is talking about an standard analog video signal, where the CC goes on the “Vertical Interval or Blanking”: the 12’5 lines per field that has no picture information. Some dedicated lines may contents CC, VITC or test signals
In digital video there is not Vertical Interval, so the CCs must go on the active picture or as metadata.
rafael
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