Determining the capture area of a capture card

[vhelp]

This is exactly what I would say. Use the resolution chart I posted. You made a dvd disc right? The ADVC and DC10 probably have lowpass filters. I would expect the 6.75MHz circle to be solid grey. You should do this at full resolution, for the reasons Arachno said. Resize is a filter. Run the test on your devices and show us ...

Hi Trev my friend.

Sorry, but above, you lost me. I'm operating up 50% stupidity this evening.
Sorry for that.

What exactly do you want me to do this evening, and I will endeavor
to make it so (captain Picard's line.. "..make it so")

Tell me which chart I need, and I'll burn it, using the .avs script
that Arach gave earlier. And, which cards did you want me to test
this out on w/ my new mobo ? ..my ATI-TV Wonder of course :)

-vhelp

[vhelp]

.
.
However, I'm still confused as to each cards "low-pass filtering"
that they employ.

As I've mentioned above, the DC10+ results in zero noise. As does
the advc-100 result in zero noise. These two devices are noiseless.
All other analog capture cards are Noisy.. no matter what chip they
employ in each (ie, are Conexant and BTxx)

I fail to understand why they all have "low-pass filters" to begin
with, topping it off w/ different one on each card as well :confused:

Here is a run down of my VCRs I've tested these cards under:

* Sharp VC H960 - (RCA only)
* Sony SLV-685HF - (older unit) - (RCA only)
* JVC S-VHS HR-S3910U (RCA/S-Video)

Note, for obvious reasons, the JVC puts out the best quality.

So far, I've tried the following cards and all produce the same level
of Line Noise:

* Osprey-210 - (RCA/S-Video)
* ATI all in wonder - (RCA/S-Video)
* I/O Magic - (RCA/S-Video)
* ATI-TV Wonder - (RCA/S-Video)
* WinTV-GO - (RCA/S-Video)
* cheap generic card - (RCA/S-Video)
* others in the past (that I returned due to Noise)

But, these all produce (pretty much) the same amount or level of Noise
in the capture .avi file.

Thanks guys,
-vhelp

[trevlac]

@V

http://trevlac.us/pics/Resolution1.png

Make a disc with the above (or put it on DV). Don't resize it. s-video please.

Play it into a card/device and capture at 720x480. In the lower right is a 6.75MHz circle. This is the max resolution for DVD/DV. It will not likely come out as clear as the png. The 4.18 circle will also be a good one to see.

On filtering. Low pass filtering means to pass the low frequencies. Since everything above a certain frequency is truely noise, this is a good way to reduce noise. A resize to a lower size is in fact a lowpass filter. Devices may do this in different ways before the signal gets digitized, regardless of the chip on board. After the signal gets digitized, other steps in the process may filter out noise. The test pattern circles are of a certain frequency. If the low pass filters do not let their details pass, they will be a flat grey in the result. They may also have some faint detail. Filters actually dampen the signal vs removing it. So the process is gradual. When it is dampened enough, it is effectively removed.

[vhelp]

@ trev,

I will see what I can do this late night.. now. I'm pushing toward
tiredness, but I'll see if I can do something anyways. Otherwise,
expect some results tomorrow :)

Thanks for the explanaa,
-vhelp

[numlock]

Arachnotron:

I have to say that you do have to do vertical calibraion also. It'looks like it doesn't capture 480 lines. Again it captures less and then resizes.

The way I found out I captured a video tape with some text at the top and bpottom of the screen. Made a DVd, played it and I could clearly see that it didn't capture it properly.

[Arachnotron]

@numlock

I have to say that you do have to do vertical calibraion also.

Not for AR calcultions. Knowing which is the first line your card captures is not important for that. Only the total number of lines is important, and that is always 480/576. But because of the variation in the starting line, some of those lines can be black. Those black lines DO count as far as AR is concerned. Basically, you are cropping some of the picture lines off and replacing them by black lines. Cropping does not change the AR, only resizing does.

It is nice to know the first line of course, but because of the variations in the way dvd players play back the first lines of a DVD, a DVD player cannot be used to determine that. (unless you calibrate your DVD player first, using a known card like the BT878/BTwincap combo)

For NTSC, capture cards seem to start at either line 22, 23 or 24 of field one, so a 6 line variation in total.

But I have found that the variation in what is the first line with VHS tape for NTSC can be a lot larger. The active area on tape can start before line 22.

For PAL, the range for the first line a card grabs is about 22-25. Here, you have a chance to see which one it is: if you cap a DVD and you have the WSS signal in your cap, you know that line is originating from 23. For NTSC, AFAIKR the WSS line is in line 10 and never shows up in a cap.

What really would be nice would be a driver that would let you adjust the first line from source to source. But so far, only the BT878/vdub combo allows you to tweak this.

[edit] be aware that your DVD player also replaces some lines by black ones on playback. Again, this does not changes AR

[dutchfudge]

Hi, I am trying to get ready for some video capturing using my new
Sapphire Theatrix card with the ATI Theater 550 Pro. Used virtualVCR w/Huffyuv.

*** I used IfoEdit to create the test DVD .img file, then burned with dvd decryptor. Plays on stand alone just fine ***

I am trying to determine the active capture window, but I'm not quite sure what to count at the edges of the capture pic.

It seems to be shifted to the right, as there are a total of 22 pixels to the left of the 20 mark, and 17 to the right of the 700 mark(some are black, some dark grey).

Could someone analyze this and give me the stats?

thanks

http://home.pacbell.net/chuckl56/video capture/dvd svideo test toshiba.jpg

[Arachnotron]

DVD pixel line 20 ends up on pixel 22 in the cap
DVD pixel line 700 ends up on pixel 702 in the cap

so, 700 - 20= 680 DVD pixels were captured in 702 - 22 = 680 capture pixels. That is exactly 1 DVD pixel per captured pixel. Which gives you 720 x 1 = 720 DVD pixels in the capture window.

This makes your capture window 720 / 13.5 = 53.333 µs wide. This would make your card an "ITU compliant" card.

So, if your target is DVD, you can simply cap 720x480 and don't do any resizing :)

The shift to the right (and the black bars at the side) may originate from the DVD player. You cannot use this method to determine the offset of the capture window because you never know what the offset of the DVD player is. This does not really matter: the capture window is so wide that the active window of any analogue source you will ever encounter falls into it anyway. (so you will always have some black pixels on either side of your cap)

[Wilbert]

I will add it to are list. Thx!

[dutchfudge]

Thanks, I had done the math and come out with 53.333333 mS, but wasn't sure. In some of the press releases the 550 pro is lauded as ITU certified, guess that confirms that the capture window is compliant at least :)

There is a NEW driver date 3-1-2005 available from ati.com. I installed and tested again with new driver, seems to be the same results.

If anyone comes across info about the theater 550 pro, send it my way!
Better yet, start a thread!

I am wondering about whether using VIrtualVCR and huffyuv is avoiding the hardware noise filters, etc built into the chip.

thanks again!

[Arachnotron]

I am wondering about whether using VIrtualVCR and huffyuv is avoiding the hardware noise filters, etc built into the chip. I don't think so. Options like that are switched on on the driver level, so unless you can set it in the driver device tab I don't expect capping with VVCR to influence it. Huffy is a compression codec, so it has no influence on the hardware whatsoever.

But it is possible the Ati software makes some hardware settings on it's own, though unlikely.

[dutchfudge]

Hey anyone who is interested,

I started a new thread in the PC Hard or Software section, and I put up some registry info, maybe someone can figure out more about the card from that.

Not sure if it is getting much attention in there though, maybe it would be better in the capturing video forum?