Capture card native (hardware) resolution??

[junkmalle]

If you create a DVD from your hires capture, with the proper field order settings

This is the DVD MPEG2, it is already created. Where do I set the proper field order?

I don't know what DVD mastering software you're using. Are you having problems once you burn a DVD? You can probably assume that any capture program that has a DVD MPEG2 setting will produce files with the correct field order (top field first), ready to burn to DVD.

[alex1234]

OK, this is what I've got:

capture from VHS tape to 704x352 MPEG2 using ATI MMC. It produces interleased file because I see lines. When I burn it to DVD using TMPGAuthor and watch it on a TV I do not see lines anymore so it looks like I have an interleased DVD!... unless my TV does not display both fields because of fields order? How can I make sure the TV is displaying both fields?

Now, fields order... by default MMC sets this:

Current frame sequence settings:
I BB P BB P BB P BB P BB I ...
Number of P frames in group - 4
Number of B frames in Subgroup - 2

I'm not sure what this all does, but this is a default and if I leave it as is would it be OK? Would my TV still display both fields?

Thanks

[edDV]

Darryl,

are you saying that if I see that my 720x480 MPEG2 created by ATI TV Wonder capture card looks like this on my PC:


I should not worry about anything, just burn it into DVD and on a TV it will be OK i.e. no combs and displaying both fields?

Alex, yes. That is what a proper capture intended for TV display will look like on the computer. Field tear is good. Learn to love it. That is what interlaced video looks like when viewed on a RGB progressive computer display. It should also look dark if it is a proper capture. Don't adjust it to look good on the computer display or it will be bright on the TV.

If you want to simulate how it will look on TV use a good viewing program like Cyberlink PowerDVD that will properly convert the interlace image for display on the computer's RGB progressive display.

Normal TV is interlace. If you have a EDTV or HDTV, then the DVD player (or the HDTV) will create the progressive image from the interlace fields. This is for normal TV, 24fps movies are handled differently.

For film and progressive sources, read this
http://www.dvdfile.com/news/special_report/production_a_z/3_2_pulldown.htm

[junkmalle]

OK, this is what I've got:

capture from VHS tape to 704x352 MPEG2 using ATI MMC. It produces interleased file because I see lines. When I burn it to DVD using TMPGAuthor and watch it on a TV I do not see lines anymore so it looks like I have an interleased DVD!... unless my TV does not display both fields because of fields order? How can I make sure the TV is displaying both fields?

Now, fields order... by default MMC sets this:

Current frame sequence settings:
I BB P BB P BB P BB P BB I ...
Number of P frames in group - 4
Number of B frames in Subgroup - 2

I'm not sure what this all does, but this is a default and if I leave it as is would it be OK? Would my TV still display both fields?

Thanks

The IBP sequence has nothing to do with interlace. It's a parameter of MPEG compression. You don't need to fiddle with it.

If your field order is backwards you will get fast-jerky motions. Instead of the fields being shown in order on your TV (remember each field is a different point in time):

1,2,3,4,5,6,7,8...

They will be reversed in pairs:

2,1,4,3,6,5,8,7...

This is quite noticable whenever there is motion. Since you didn't mention anything like that you're probably fine.

[alex1234]

EdDV, thanks!

If you want to simulate how it will look on TV use a good viewing program like Cyberlink PowerDVD that will properly convert the interlace image for display on the computer's RGB progressive display.

1. That is what I'm using. By the way, does it really display both fields or do some tricks to filter out or 'merge' ? In other words do I loose details watching an interleased MPEG2 with PowerDVD versus regular TV?

About brightness - I've noticed this myself while experimenting with capturing. I've also noticed that I have to overcolor the image while capturing because on a TV colors looks weaker.

junkmalle, thanks!

2. How can I control fields order? Is it determined during capturing (encoding) ot viewing (decoding)?


3. And an other interesting thing I've noticed: capturing to a 352x480 MPEG variable speed with max 8 mb/sec, average 4 mb/s produces exactly the same file size as 704x480 with the same bitrate settings!! I can not explain this unless the horizontal resolution is not a 'resolution' but something else, like for example a sorts of a resizing code for a playback?? Otherwise, if it was a real resolution it would increase number of horizontal details causing the file size to inrease as well!

Please, help me to understand it!

[junkmalle]

1) PowerDVD performs a bob deinterlace. Essentially, it displays one field at a time, just like your TV. It's slightly different than your TV though. On a TV every other scanline is left black while displaying a field. Bob deinterlacers usually fill those black lines with pixels that are the the average of the pixels from the line above and the line below.

2) Field order is determined at every stage of the process. Capture hardware usually captures with a fixed field order. When you convert the video via software you can usually control the field order (you can specify the field order of the source and the output). Finally, the device that converts the digital video back to an analog signal for display can control the field order. Remember, each FRAME of video contains two FIELDS. The field order is simply which of those two fields was recorded first, and hence which should be displayed first.

3) Of course the two files were the same size: bitrate times running time = file size. That is, bitrate and running time are the only determining factors when it comes to file size. But if you have insufficient bitrate for a large frame size you will lose picture quality. For example if you compress an hour of 352x240 with a bitrate of 1150 kbps (VCD settings) it will produce an MPEG file of about 500 MB (excluding audio) that may be watchable. If you use that same bitrate on a 720x480 frame size (four times as many pixels per frame) the resuling file will be the same size, but picture quality will likely be very poor -- there simply aren't enough bits per frame to encode a good picture.

[alex1234]

Thanks junkmalle! Understood.

Now, back to the start - at the beginning I mistakenly thought that I needed a 'tuned' BT8x8 driver because I thought that ATI's one did not support interlacing. Now, thanks to all the experts who helped me in this topic, I see that ATI's driver is perfectly OK. The question: why do people
do not like 'official' drivers and prefer to use ones from 3-rd parties (which, needless to say, kept crushing my system)? Is there anything in these drivers that I did not have with ATI's and I would want to have?

[junkmalle]

alex1234, I don't have a BT8x8 card, I only know what I've read, mostly here at videohelp.com. What I understand is that the BT hardware captures at a certain resolution. If the software captures at that same resolution you get good results. But if the software is capturing at a different resolution it needs to stretch or squish the image that comes from the card. Many drivers will give noticably fuzzier pictures as a result.

I don't remember the exact numbers but the BT hardware actually captures at something like 688x480. If your software captures at that size and then pads the edges with black pixels to give a final size of 704x480, or 720x480, you get the cleanest results. Some drivers do this, others don't. If you search these forums you'll find more precise descriptions of this phenomenon.

[dphirschler]

I like the btwincap driver because it gives me a bigger capture frame. In other words, the left and right 10-20 pixels were being cropped off using the stock Pinnacle driver. So I was not only getting less image data, the aspect ratio was screwed. Btwincap driver corrected that.


Darryl