Question re component recording - AVS Forum
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post #1 of 11 Old 08-03-2001, 08:41 AM - Thread Starter
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Stupid question follows:

How does the bandwidth of *each* component compare with a single S-Video input? So, for example, if you were to compare the Yb bandwidth to S-Video.


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post #2 of 11 Old 08-04-2001, 01:01 AM
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"Stupid question" may be close on target. Not trying to be funny but since your title talks about recording and your question says S-Video which generally refers to a method of video signal transmission. However, maybe I can briefly describe each recording process and you can pull enough info to answer your real question.

S-Video generally refers to Y/C video signals of a "component" video as in Luminance and Chrominance. It is most closely related to Hi8 or SVHS recording tape formats, but since it is just a way to convey video signals in the lowest form of component, it has been used to carry other video from other tape formats as well. eg. I have Y/C or "S-Video" I/O on my betacam SP recorders. Y/C video format is a color under or heterodyned video format using a color subcarrier for the color information. The subcarrier is at 3.58 Mhz.

When this color under video is recorded as in Hi8 or SVHS recording it is simply recorded as a "Composite" single track. Therefore there is no true maintaining of the Y/C components in the actual tape for Hi8 or SVHS. This is not so with true component recording, such as betacam where the components Y, R-Y, B-Y are recorded to two adjacent video tracks. One carries the Y, and the other carries both the R-Y and B-Y in a "C" track where these two signals are multiplexed. This is done with in such a way that it can be later separated into the two color difference components in a near perfect manner, resulting in the three discretely separate components on playback. No hetrodyning is used and the color purity is maintained.

So, with that understanding you can now examine the "bandwidth specs for the two different video tracks on tape.

In betacam SP:
Y- 4.5 Mhz
C1- 1.5 Mhz.
C2- 1.5 Mhz.

In SVHS-
The chroma is 1.5 Mhz and the Y is 1.6 Mhz but at a center carrier freq. of 7.0 Mhz. The Y and C are combined as a color under video signal when recorded on tape.

Bottom line is you can't simply single out one measurement and make a comparison.
The same goes for comparing digital tape formats with analog, by using bandwidth. In some respects the bandwidth may be higher as in the case of DVCAM 5.5Mhz vs. Betacam 4.5Mhz but in the case of color information the sampling for DVCAM is less than the color bandwidth ratio for betacam.

The way I keep all this straight in my head is to simply compile all the performance plusses and minuses for each tape format and then know that for one recording purpose, this format is the best and for another purpose another format will be better.

Using my video production company as an example, I use DVCAM and Betacam SP. I know that for reliability, to get the shot, DVCAM is superior. It has much better dropout specs, better recording time, better audio noise floor, and slightly more saturated colors. However Betacam SP is better for industry wide compatibility, better for shooting footage for chroma keying, and produces less artifacting from compression during the edit process and has no aliasing on hard diagonals like DVCAM has. As a videographer, I prefer to evaluate all tape formats based on overall performance for the job at hand. As an engineer, I can sit and chart the numbers, but they mean squat in the real world of actual shooting and editing.

Now, the only thing "stupid" about your question is the idea that you can make a "bandwidth" comparison between your choices and have it mean anything significant and that's an engineering fact. In otherwords, its not the data that is stupid, its how one may interpret the data that is.

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post #3 of 11 Old 08-04-2001, 08:31 AM
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How good is a DVCAM machine at recording component video?

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post #4 of 11 Old 08-04-2001, 02:15 PM - Thread Starter
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Thanks for clarifying the difference between my implied stupidity and my actual stupidity!

What I was getting at is how many 3/4" tapes would it take to record the analog signal from each component of a component output from a high definition source. I thought if it was less than or equal to 1 including timecode, perhaps something could be rigged up to synchronize three tape decks or something...but I have since learned about W-VHS, anyway, and it seems to do the same thing on a single tape.
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post #5 of 11 Old 08-06-2001, 08:59 PM
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Ken-
The DVCAM format is excellent at doing component recording. It is basically equal in quality to betacam SP. I shoot both using identical camera heads and lenses.
Then mix both in post and it is very difficult to see any difference. But, DVCAM is an SD format.

Aviators99- I really don't understand what you are trying to achieve with the 3/4" tape thing. You may be talking about rigging 3 Umatic machines but I don't know why? Seems like an awful lot of trouble.

There are all sorts of ways to record HDTV available. Most are not economical. The best solution I have seen for the money is the Panny DVHS combo with excellent quality, DD audio and very low cost media. Next would be the WVHS format but this has a high media cost and is restricted to analog audio. Beyond that you are into the pro machines, DVCPROHD, HDCAM and D5. There is a big price jump between the DVHS/WVHS and the pro machines.
It seems the options are that you use the DVHS Panny combo for HD recording off the DishNetwork and OTA, and you use the WVHS for recording DirecTV programming off the Sony RGBHV output. I understand that the WVHS recorder will not sync to the DTC-100's RGBHV output, however Extron may have a solution to this but at a pricey fix. Cheaper to get the Sony receiver.

I suspect that the recording problem for HDTV will soon be over, with either a PC board for time shifting or some new product introductions to the consumer market.


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post #6 of 11 Old 08-06-2001, 10:29 PM
 
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Umatic is composite out only and uses short length tape. 1/2 inch prosumer SVHS would be a better choice!
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post #7 of 11 Old 08-10-2001, 06:23 AM
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Don,
You are slightly mistaken
DV formats are not Native SD
They are native DV In a serial stream
DV is 5:1 compression
Take dv to analog a couple of generations and you will see the difference.
DV is fine if you edit DV and master DV
But it is not comparable to beta
Shoot a Radial resolution chart and you will see.
{Or Record multiburst}

When I say Beta im referring to real beta decks (PVW, BVW)
Not the low end UVW viewing machines
They are not the same format (AUDIO)
And should not be used with clients that you want to keep
DV is not on par with Beta (which does mild croma compression).

DV is a great Prosumer format that is being used
in a lot of news and lower end post operations.
Where quality is not quite as important
I have several clients that are very happy with it.


The bandwidth statements on your post seem correct
(I tip my hat)

Back to the original question
S-video is the consumer version of "component"
Its better than composite but nowhere near RGB
Recording it on 3/4 makes no sense
Get a hi-pix card and some hard drives

BTW w-vhs records the 19 mbs ATSC stream if im not mistaken
(which I could be, I don't have one)

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post #8 of 11 Old 08-10-2001, 08:44 AM
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woowoo-

Sorry for the abbreviation confusion. Please re-read the statement about DVCAM thinking that SD is Standard Definition as opposed to HD or High definition. I know DVCAM is native dv format! and I did not mean Serial Digital.

I won't succomb to the 8 year old pissing contest on UVW-PVW-BVW grade decks. Nobody except small production companies that got their ass kicked by having too much money tied up in those higher end format decks care. Especially since the quality performance, and maintenance costs over the years are well established for the three grades and the UVW has proven itself worthy in all lower budget but very profitable TV production. I've been in the business for 16 years and know full well what that pissing contest is all about. To sum it up, there is absolutely no truth to claims that owning a BVW is necessary to keep a client. Only that if you must use BVW then you will be best served with that level of equipment. There is much truth that matching a given quality of equipment to your client's needs and budget will keep your business profitable, clients happy, and give them the product that works. Your TV station may require that level, my production company does not!
While you may be a pretty bright Broadcast Engineer and can quote bandwidth specs off the top of your head, you should realize that there is far more to running a successful TV production company than just knowing how the various formats work. Simply put, you have to know how to create a finished production that satisfies the needs of your client and generates a profit for you. The engineering side of this formula for success is only a small but important part of the formula.




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post #9 of 11 Old 08-10-2001, 08:59 AM
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Don,
I was just trying to clear up the facts

DV is NOT the same as Beta

Sorry to ruffle your feathers

Use whatever Equipment you like

OK?

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post #10 of 11 Old 08-10-2001, 08:26 PM
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Agreed, DV or DVCAM is not the same as beta. I was only stating that is can be easily mixed with beta in production and edit with differences that few will see. You will and I will but 99.99 % of the people I work for won't.
I'll tell you what I look for in general footage- Aliasing on diaginals on DVCAM that is not present on beta. Tear drop shaped tape dropouts on horizontal lines on beta SP that never show up on DVCAM. Also, when I shoot DVCAM or betacam, I use the same lens and camera head with a dockable backs for each of the format so the video is identical. The betacam SP is a BVV-5 or a PVV-3 and the DVCAM is a DSR-1. While the BVV-5 is older it produces those AFM tracks for the few clients who request it. And I have record review that the PVV-3 does not. Both have the same video PQ.

We rarely do chroma key work but I do have a fair amount of experience with it. I carry a portable 10'X10' green screen/blue screen on the back side in my production van at all times. When I shoot for keying, I use betacam as DVCAM does have poor edge definition on the keys. Yes I know why but won't bore people here with the technical reasons why. Other than that, I find that in the distribution master on beta SP, whether it was shot on DVCAM or betacam SP it really doesn't matter.

Also, check your PM on this forum. I sent you something to try to look at for your opinion.

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post #11 of 11 Old 08-10-2001, 08:47 PM
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Well, from the novice,

Neither Betacam or DVCAM is HD but I'm sure that they beat the pants off of NTSC and S-video.

I might be able to get a cheapy on eBay at some point and I can use it with component input from a standard STB.

How will it compare with DVD quality for archiving?



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