Welcome to Doom9's Forum, THE in-place to be for everyone interested in DVD conversion. Before you start posting please read the forum rules. By posting to this forum you agree to abide by the rules. |
3rd September 2003, 22:46 | #21 | Link |
Registered User
Join Date: Feb 2002
Location: Charlotte, NC USA
Posts: 1,984
|
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.
|
3rd September 2003, 22:57 | #22 | Link | |
Registered User
Join Date: Jul 2002
Location: Canada
Posts: 196
|
Quote:
There is of course the next issue of which resizer to use. :-) |
|
3rd September 2003, 23:10 | #23 | Link | |
Registered User
Join Date: Oct 2001
Location: Lands of confusion
Posts: 1,217
|
Quote:
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 |
|
4th September 2003, 02:07 | #24 | Link |
Registered User
Join Date: Feb 2002
Location: Charlotte, NC USA
Posts: 1,984
|
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. |
4th September 2003, 10:40 | #25 | Link |
Registered User
Join Date: Oct 2001
Location: Lands of confusion
Posts: 1,217
|
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... |
4th September 2003, 11:20 | #27 | Link | |||
Registered User
Join Date: Feb 2002
Location: Charlotte, NC USA
Posts: 1,984
|
Quote:
Quote:
Quote:
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.
__________________
Reclusive fart. Collecting Military, Trains, Cooking, Woodworking, Fighting Illini, Auburn Tigers |
|||
4th September 2003, 14:19 | #28 | Link | |
Registered User
Join Date: Oct 2001
Location: Lands of confusion
Posts: 1,217
|
Quote:
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. |
|
4th September 2003, 15:15 | #29 | Link | |||
Registered User
Join Date: Jul 2002
Location: Germany
Posts: 819
|
Quote:
Quote:
In 704/720/768 you always get EXACTLY the same Picture, only the PAR is different. Quote:
|
|||
4th September 2003, 15:45 | #30 | Link | |
Registered User
Join Date: Oct 2001
Location: Lands of confusion
Posts: 1,217
|
Quote:
|
|
4th September 2003, 17:38 | #31 | Link | ||
Registered User
Join Date: Jul 2002
Location: Germany
Posts: 819
|
Quote:
Quote:
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. |
||
4th September 2003, 18:33 | #33 | Link |
Registered User
Join Date: Oct 2001
Location: Lands of confusion
Posts: 1,217
|
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'. |
4th September 2003, 19:59 | #34 | Link | |
Moderator
Join Date: Nov 2001
Location: Netherlands
Posts: 6,364
|
@Kika,
Quote:
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? |
|
4th September 2003, 21:18 | #35 | Link |
Registered User
Join Date: Oct 2001
Location: Lands of confusion
Posts: 1,217
|
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'. |
5th September 2003, 08:25 | #36 | Link | |||
Registered User
Join Date: Jul 2002
Location: Germany
Posts: 819
|
@ ppera2
Quote:
And yes, that's the same way i calculate it. Quote:
Quote:
@jggimi I agree to ppera2. That's not a heavy discussion or a flame war. |
|||
5th September 2003, 09:15 | #37 | Link | |
Registered User
Join Date: Oct 2001
Location: Lands of confusion
Posts: 1,217
|
Quote:
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. |
|
5th September 2003, 09:43 | #38 | Link | |
Registered User
Join Date: Jul 2002
Location: Germany
Posts: 819
|
Quote:
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. |
|
5th September 2003, 10:17 | #39 | Link | |
Moderator
Join Date: Nov 2001
Location: Netherlands
Posts: 6,364
|
@Kika,
Quote:
How many lines does a scan line include, when talking about tv's? |
|
Thread Tools | Search this Thread |
Display Modes | |
|
|