Capture Calibration

[Shandra]

Hi Folks,

As I now have a TV-Capture Card based on the SI3174 Chipset I went through some research regarding all the aspect ratio stuff - ended up with too many information that sometimes was contradigting itself... So I went for some simple test to figure out my capture ratio...
Basic setup ->
a) (done with every new monitor, but for completeness I am mentioning it here) Colour Calibration (thanks for those old foil and program that came along with older matrox cards), then resizing the Output via the OSD of the monitor so that a X x X cm square in monitor dpi was actually displayed in that size, etc.)
b) Made a Testpicture with a circle and 2 lines (like a sniper sight), converted that to an avi and captured that with my VHS (the convertion to avi so that I don't needed to enable the second monitor (and changing the drivers for it to TV), but simply used my G450 DVD-max to send the overlay over the TV/2ndMon Line)...

Test Procedure ->
a) I then captured that VHS using different res. (768x/720x/704x 576)
and then extracted a single frame as an image from each recording.
b) I loaded that pictures into my GFX program and placed a circle over the captured one....

results ->
In 768x576 the captured hor.rez was a bit stretched, in
the other two a bit shrinked... 720x756 gave the best result... I then resized the hor. axis to fit the overlayed circle - wich for all 3 was at x=~734.... I verified that with a TV Capture from a channel that uses a circular logo (checked that on my TV) and that confirmed with the resize to 734 to be circular again...

OK, nevertheless now my questions...
With my approach are there some fundamental flaws I have missed ?
If not; using Huffyuv is a nogo to resize to 734x576 as I end up with some strange looking (diagonal messed up picture in BW) result.... so what should or can I do to resize the video (I wanna stay with a lossless codec during that part)?
And for later processing:
As long as i only use that material on a pc, is there any need to actually use a 4:3 Aspect in the final?
Ok, I think I end for now - as I will continue with my research for aspect ratio stuff and maybe I am coming back on that later....

CU,
SHAnDRA

[^^-+I4004+-^^]

>With my approach are there some fundamental flaws I have missed ?
If not; using Huffyuv is a nogo to resize to 734x576

probably some flaws you did:(it's too late to
read carefully..heh)
you should know two things:

ALL pixels watched on monitor are SQAURE
(all of them!)
MANY tv-out chips will output sqaure pixels too
(dunno 'bout matrox,it might be some exception
but i doubt it can correct sqaure pixelAR to
the unsqaure video (ccir601) pixel an-the-fly...)
so draw your conclusions.....
(i think you must have dvd-player and burn some
720x576 and 480x576 and analyze that to ne sure of it)

anyhow,your method is very interesting and a breath of
fresh air (althtough this square and unsqaure pixels might drive you mad...heh)
734x576 seems pretty funny res. for huff,no wonder it has problems....

here's what you might try;
capture VHS tape 3 times (yeap,768,720,704 x 576),make
your end format from that (resize as you wish) and see what
resolution resembles the original VHS (as displayed on tv)
the most.....
(for sqaure pixel it should be 768x576,and for mpeg2 dvd compliant video it would be 720x576)

>As long as i only use that material on a pc, is there any need to actually use a 4:3 Aspect in the final?

no,not at all!
use some player that can correct AR (zoomplayer for example)...
you can have 480x576 or 352x576 with some real funny AR's
and "4:3" ticked in zoomplayer it looks like million $....
(then,for matrox "divx g400" is nice solution for non32 resolutions
etc.)
if you encode leterboxed stuff(and go for leterbox
divx resolutions),then it's not so easy as you have to keep the source AR (during playback) to have correct AR

btw.google didn't speak to me about "SI3174 "..
what's that chipset?
is it "Philips 7134" typo?

btw2.are you a girl?
(hehe)
ps1:"sqaure" pixels?heheh


/ivo

[Shandra]

Hi Folks,

^^-+I4004+-^^:
yup, typo - was the Philips...
Ok, fine tuned (or better to say I spend more time on my comparison) the picture and now my best fit is with 732x576 - and with that Huffyuv has no problems....

Yeah, the TV Out was something that concerned me, so i have choosen my Matrox to do it, as I have no trust in ATI with that (my PC on wich I capture has an ATI)... as the displayed picture on the TV was good (perfect circle) I just could hope that they know what their drivers should be doing ;)

And yes, I verified it as I mentioned with the circular logo from a TVStation (sadly at cable-times they no longer send a test-picture during their OffTimes), and last night with some VHS Material, seems that at 732 I have the same sized picture on my PC as on my TV - but I will do some further tests with a larger TV (My Granny is off for vacation next week and so I stay at her home during that time and could use hers).

As you mentioned I wish I would have a DVDPlayer or at least an old console that could play CDi - but I will do that on some LAN-Weekend where our host owns a DVDPlayer...
And i am in need of that test just because if I send the resized video back to the TV it ends again only in the displayed Area of the TV and so is shrinked again but circular (capture again, resize to 732 still good on PC) - but I do need to check what happens if it is send by a non-PC source.... but until then I at last could backup my old recordings to PC and DivX - and maybe I have to do it again if I want to make some SVCDs/DVDs from my holiday recordings for standalone players...
Or maybe I don't really need that test - some answer I still has not found was if a standalone device sends the whole picture to the display Area of the TV (like the TV out of GFX-Cards) or to they send it to the whole range of the signal (Was nice to see that with my VHS Tapes and TV I never have sawn the whole Picture) -> so much more I have to seek out in information ;>

CU,
SHAnDRA

P.S.: No, not a girl - I used that name since the early 1990's as a nick, made up from SHAdow aNd DRAgon... just in 2001 or 2002 it came to my notice that it also is a regular AngloAmerican Name for a woman - sigh....

[Shandra]

Sigh-still experimenting...
And yes I need that standalone player for further checks...
As I now noted that with larger squares a 768x576 capture is the best fitting captured picture (Intro of VHS Tapes), but with smaller rectangles in it it still comes down to a resize to 732 - so I guess that the spherical aberation by the TV-Screen is for larger areas something I can't ignore anymore... grmpf, I hope that TV of my Granny is a FlatScreen... damned :/ Yeah, that standalone - to see how far off a captured picture is compared to a ripped picture... mh, now don't tell me that the methods used by PC-DVD players are something i should be concerned about... ok, a feed through DVD2AVI and Avisynth with an unmodified size... or is that also a problem - Argh, I wish i never have felt the desire to backup my old tapes (wich are at the edge of their lifetime - my oldest are slowly turning to dust...)...

CU,
SHAnDRA

P.S.: The TV Stations are using different signals? Just noted that a circle used by those that are now broadcasting digital-streams (even if i get them analoge via my cable - but they must be transfered as you can note some typical black/white codec bars on top of the picture) seem to be best in 768x576, those that are still pure-cable stations are best in the 732x size... sigh...