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Old 3rd September 2003, 22:46   #21  |  Link
FredThompson
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Another option is to capture at 720x480 then crop to 704x480 before resizing. Most broadcasts aren't centered and if you keep the black edges you'll be averaging them into "good" data. The other aspect (there's a dangerous multiple-meaning word for a video processing forum) is you'll have more "good" data and a true halving of resolution of the actual image you want.
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Old 3rd September 2003, 22:57   #22  |  Link
Piper
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Quote:
Originally posted by FredThompson
Another option is to capture at 720x480 then crop to 704x480 before resizing. Most broadcasts aren't centered and if you keep the black edges you'll be averaging them into "good" data. The other aspect (there's a dangerous multiple-meaning word for a video processing forum) is you'll have more "good" data and a true halving of resolution of the actual image you want.
That's a good point. I've been doing precisely that with my VHS captures which are often way off center. The difference was that I wasn't cropping to exactly 704 before resizing.

There is of course the next issue of which resizer to use. :-)
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Old 3rd September 2003, 23:10   #23  |  Link
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Quote:
Originally posted by FredThompson
Only if you don't plan to filter and you trust the internal rescaling to be proper...
Filtering can be performed while not changing resolution.
Trust ot not the internal rescale - we can't avoid it.

Btw. I dl.-ed datasheet, and it's true about fixed sample.
http://www.linuxmedialabs.com/lml33doc/Bt878.pdf
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Old 4th September 2003, 02:07   #24  |  Link
FredThompson
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Sigh...capture at as high a resolution as possible, then filter, then resize.

Filter before resizing so you have as much data as possible for the filtering. Resize after that with a method which you know is high quality to reduce distortion as much as possible.
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Old 4th September 2003, 10:40   #25  |  Link
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Yes, that's all right. But, when quality of TV video is already poor, it has not much sense. Other thing is time and resources required for max. quality capturing and postprocessing.

In any case, I go on digital SAT capturing from now (actually not real capturing). Quality is far superior, no noise etc.
And it's often in DVD format already. Cards are pretty cheap now...
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Old 4th September 2003, 11:09   #26  |  Link
Kika
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Quote:
Another option is to capture at 720x480 then crop to 704x480 before resizing.
Not on BT-Cards. They don't do a proper Scaling to 720. All you realy get is the same Pic like in 768 or 704.
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Old 4th September 2003, 11:20   #27  |  Link
FredThompson
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Quote:
Originally posted by ppera2
Yes, that's all right. But, when quality of TV video is already poor, it has not much sense.
Did you even read the first line of the first post?
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Other thing is time and resources required for max. quality capturing and postprocessing.
When did the original poster say this was a problem?
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In any case, I go on digital SAT capturing from now (actually not real capturing). Quality is far superior, no noise etc.
And it's often in DVD format already. Cards are pretty cheap now...
Irrelevant. You're in Europe, the first poster is in America using DirecTV and digital cable. DirecTV is not DVB.

I have DirecTV and have done capture at 720x480 and converted to both CVD and SVCD resolutions. SVCD looks better.

Seems you lost track of the reason for the thread.
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Old 4th September 2003, 14:19   #28  |  Link
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Quote:
Originally posted by FredThompson
[B]Did you even read the first line of the first post?When did the original poster say this was a problem?

Beg your pardon???? This was reply to you, not to thread starter, who is not anymore in discussion. New discussion started after 'discovering' how BT878/9 works.


Irrelevant. You're in Europe, the first poster is in America using DirecTV and digital cable. DirecTV is not DVB.


I don't know why you react so. Should I talk here only strictly things related to first post? You lost track about how discuss on such forums.
Anyway, maybe you and others in USA should start think about how record digital video without D/A - A/D spoiling.

I have DirecTV and have done capture at 720x480 and converted to both CVD and SVCD resolutions. SVCD looks better.

I agree

Seems you lost track of the reason for the thread.
Reason for the thread is to learn something, to exchange opinions. Not to talking to people where live, and because of that not to do this and that.

Btw. your whole often repeated opinion about 'illegal' resolutions by capture is pretty senseless. I can capture in lot of horizontal resolutions, without any black border left and right. And how I will scale it is irrelevant for capture (and it's quality) itself.
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Old 4th September 2003, 15:15   #29  |  Link
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Quote:
Btw. your whole often repeated opinion about 'illegal' resolutions by capture is pretty senseless.
It isn't


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I can capture in lot of horizontal resolutions, without any black border left and right.
Still not understanding? That's exactly the problem.
In 704/720/768 you always get EXACTLY the same Picture, only the PAR is different.


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And how I will scale it is irrelevant for capture (and it's quality) itself.
And that's not true. It's a difference to Resize 2 Pixels to one or 2.045 to one...
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Old 4th September 2003, 15:45   #30  |  Link
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Quote:
Originally posted by Kika
...
Still not understanding? That's exactly the problem.
In 704/720/768 you always get EXACTLY the same Picture, only the PAR is different.


Source is same, but digital interpretation is not same! How can be same 704 with 768 pixel???? AR is not so important here. I can correct it by postpro. or by playback.


And that's not true. It's a difference to Resize 2 Pixels to one or 2.045 to one...
Right. But you don't know what is my target res. And we stated here that BT 878/9 does internal resize. So better capture in moduo of internal resolution - if you can. However, I don't see difference in captures at 720 or 704 with BT 878.
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Old 4th September 2003, 17:38   #31  |  Link
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Source is same, but digital interpretation is not same! How can be same 704 with 768 pixel????
That's a point we had before. I wrote Picture, not Pixels. All three Resolutions do show you the same Picture. The difference is the amount of Pixels and their AR (the PAR).

Quote:
But you don't know what is my target res
At last, we talked about Half-D1-Resolution.
And then, there IS a difference between capturing 704x480 and resize to 352x480 and capturing 720x480, cropping to 704x480 and resize to 352x480.

If you goal is to capture as many Pixels as possible, then 768x480 may be a good choice. But for Half-D1, the best you can do is capturing exactly double the amount of Pixels needet.
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Old 4th September 2003, 17:43   #32  |  Link
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Please try to calm down, people, and be as polite as possible. Thank you.
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Old 4th September 2003, 18:33   #33  |  Link
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I don't think that Kika and me have some heavy discussion here. There are only slight differences, and as I see we start to closing.

Just to say that by capturing we always have same picture - but it's, I think very bad formulation. Better to say video. And we can't never get exact 'picture' by digitalising, just closing to it. Difference is not just amount of pixels and AR, but what is most important: that at higher res. we go closer to 'exact picture'.
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Old 4th September 2003, 19:59   #34  |  Link
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@Kika,

Quote:
One Line is the Time for "drawing" a complete Sine-Waveform (argh, my english-problem again). It is the periodic Time of the Waveform.
I guess you are right, but I don't understand it. Maybe you can clear it up?

The frequency of the waveform is 4.43 MHz (pal), thus the period is 2*pi/4.43 = 1.42 ms.

But I guess you can also calculate the period in the following way: The duration of a frame is 1/25 = 40 ms, and thus 40/576 = 0.0694 ms per line. Or should I take the total number of scan lines, thus 40/625 = 0.064 ms.

Why are the two periods (1.42 and 0.0694/0.064) not equal?
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Old 4th September 2003, 21:18   #35  |  Link
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Wilbert:

Time of waveform by analogue video should be calculated somehow so:

We have max bandwith of video signal, and it should not be mixed with freq. of chroma carrier. By CCIR (PAL) TV it's about 5 Mhz. So we can calculate that one period is 200 nanosec long. By VHS bandwith is much lower, and on other side, by studio tapes is higher.
One horizontal line is 64 microsecond long, but we have horizontal blank of about 12 microsec, so can calculate that active part of line is about 50 microsec. Dividing it with 200 nanosec we get 50x5 periods. This 250 period per hor. line means 500 changes, or 500 pixels. Sampling freq. must be at least twice as bandwith, what is explained many times. But as much higher, more accurate.

Your first calculation is btw. total wrong, you don't need any pi and chroma carrier freq. here. Right is that 40/625.

As I see Kika's explanation is very confusing, but one line is not for writing 'complete Sine Waveform' It can write much more periods, as I explained at begin, depending from source (capability). Plus, sineform is just theoretical, real video is random. '240 lines' (VHS, I guess) should be for vertical lines, but it's better say just 'pixels'.
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Old 5th September 2003, 08:25   #36  |  Link
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@ ppera2

Quote:
One horizontal line is 64 microsecond long, but we have horizontal blank of about 12 microsec, so can calculate that active part of line is about 50 microsec.
52 microsec.
And yes, that's the same way i calculate it.

Quote:
As I see Kika's explanation is very confusing, but one line is not for writing 'complete Sine Waveform' It can write much more periods
Maybe my explanation was a little clumsy. I talked about horizontal Lines, not the Scan Lines. At VHS-Bandwith, each Scan Line can include up to 240-250 horizontal Lines, and each horizontal Line is one periode. Guess that's more clear, isn't it?

Quote:
Plus, sineform is just theoretical, real video is random.
Right. But Sineforms are used as a measurement for the horizontal analogue Resolution.

@jggimi
I agree to ppera2. That's not a heavy discussion or a flame war.
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Old 5th September 2003, 09:15   #37  |  Link
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Quote:
Originally posted by Kika
@ ppera2
Maybe my explanation was a little clumsy. I talked about horizontal Lines, not the Scan Lines. At VHS-Bandwith, each Scan Line can include up to 240-250 horizontal Lines, and each horizontal Line is one periode. Guess that's more clear, isn't it?
Why you say that Scan Line include up to 240-250 horizontal lines.... ?

Scan line is a horizontal line. It can include pixels. I don't see about what bandwith you talk - VHS or TV? Why say that each hor. line is one periode? Hor. line can include many periods depending from bandwith. It's nothing more clear, I think
Is this some direct translation from German? I doubt it, but you can write it te mo in German, i can uderstand it.
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Old 5th September 2003, 09:43   #38  |  Link
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Quote:
Why you say that Scan Line include up to 240-250 horizontal lines.... ?
Because that's what the Specs are saying about that.
But if you don't like those term, you can say it this way:

A Scan Line includes up to 250 Lines (VHS). But that's not clear.
Way 2: A Scan Line includes up to 250 periods of a Sine Waveform (VHS).

Don you know some technical Manuals from Camcorders or VCRs? They are "talking" about things like "Resolution, better 400 Lines". These Lines aren't the Scan Lines, because PAL have to have 576 and NTSC 480 Scan Lines, right?

And that's also where the Myth about VHS-Resolution started. The Manuals of most VHS-VCRs are talking about 220 to 240 Lines - and most people are still beliving, these were Scan Lines. But analogue Resolution has (Horizontal) Lines per Scan Line as it's measurement.
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Old 5th September 2003, 10:17   #39  |  Link
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@Kika,

Quote:
Because that's what the Specs are saying about that.
But if you don't like those term, you can say it this way:

A Scan Line includes up to 250 Lines (VHS). But that's not clear.
Way 2: A Scan Line includes up to 250 periods of a Sine Waveform (VHS).

And that's also where the Myth about VHS-Resolution started. The Manuals of most VHS-VCRs are talking about 220 to 240 Lines - and most people are still beliving, these were Scan Lines. But analogue Resolution has (Horizontal) Lines per Scan Line as it's measurement.
Interesting! Do you have some references/books which explains this stuff a bit (ie. line = one period of a Sine Wavefrom, etc.)?

How many lines does a scan line include, when talking about tv's?
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Old 5th September 2003, 10:19   #40  |  Link
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I see. Those lines are actually vertical lines - resolution better than xxx VERTICAL line. Vertical is often not accented. And you wrote it like horizontal, what is of course wrong.
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