Black strip down left hand side

[DarrenD]

Has anyone seen this before.

I am using Win2K+SP3, Matrox G400-TV Marvel, PowerDesk 5.85, Video Tools 2.04.015 (official, not leaked), AVI_IO (licensed, not trial), PICVideo (settings 20, 2 fields >288).

When capturing at 704x576 I get a black strip down the left hand side. When captuing at 352x288 I don't get it.

Can anyone help?

[Dr Mordrid]

This topic comes up regularly, so your not seeing things

The black border on the left is normal with the Matrox Marvel/RRG. You may also notice some noise at the top of the capture. This is also normal and falls within what is called the "overscan" area. Both will be cut off when displayed on a TV.

If you find that these areas interfere somehow editors like MSPro and Premiere have cropping filters for such things.

Dr. Mordrid

[DarrenD]

I guess you are saying it is a capture problem in the Marvel/RRG driver so there is absolutely nothing I can do about it, apart from ditching the Marvel.

Oh well!

If I put a 8 pixel crop on the left and also on the right (to even it up) borders should I keep these on any video to prevent a rescaling from 560 (576-2*8) up to 576 again?

This question also will apply when cropping (if that's the word) to make 704x576 up to 720x576 when making a DVD. I assume that when I get MSP7 it will allow me to add extra height (I could not see how to do this in VirtualDub).

[Dr Mordrid]

The real issue is are you going to display the full sized videos on a TV?

If the answer is yes then you're fixing a problem that doesn't need fixing since that black bar won't show up on any normal TV set anyhow.

Dr. Mordrid

[Brian Ellis]

Darren

As Doc says, this is a non-problem. What you are seeing is the part of the picture which is used for technical bits and pieces, like synch pulse platforms. Before and after the blacker-than-black synch pulses, there is a short period at black level, which is used so that the TV set knows where black is. and can adjust the line accordingly. These black-level platforms are never seen on a TV as there is always a few per cent overscan, left and right (also top and bottom for teletext as well as the frame/field series of synch pulses). On a 'puter monitor, these are visible because the TV synch pulses are treated by the graphics cards differently, because there is no necessarily mathematical relationship between the TV frame/line rates and the monitor frame/line numbers and rates. It would be frankly silly to try and get rid of them, because the software will only re-establish them, as they are an essenytial part of the signal. OTOH, I agree that Marvel and other G-series Matrox graphics cards do tend to make them a little predominant, possibly because they operate on the leading edge of the synch pulse, rather than the integrated value, leaving a longer black period.

IMHO, leave well alone because you are working with video and video is intended to be viewed on a TV set, where you will NEVER see them.

[DarrenD]

I've got the point about the overscan.

Yes, I am aiming to end up with our lovely kids' actions stored on DVDs rather than VHS so we can watch them forever without deteriorating quality on a TV.

Therefore, I can ignore correcting the capture program (a: because I can't and b: because it doesn't matter).

My next question then is (as I think I understand it) that when I encode to DVD the perceived quality is down to the bit-rate and how much "stuff" there is to compress. Now I know that compressing lots of black should take little space whereas compressing lots of video will take more. Therefore, should I crop the left and right in MSP7 (when it comes out! - when is that?) by <n> pixels and then add <n> pixels of black (since I won't be able to see it on the TV anyway). In my way of thinking the non-visible black should allow more of the bit-rate for compressing the visible screen area.

Does this make sense, or am I talking rubbish, or even theoretically correct but in reality has no visible difference.

Thanks

[Dr Mordrid]

Again; why bother?

DVD supports 720, 704 and 352 wide video and the black, of course, will be automatically cropped when it's played on a TV.

DVD compatable list;

NTSC

720x480 MPEG-2 (CCIR/ITU-601 D1)
704x480 MPEG-2 (ATSC Table3 D1 for 4:3 SDTV)
352x480 MPEG-1 and MPEG-2 (half D1; often used by cable/satellite to cut the bitrate)
352x240 MPEG-1 and MPEG-2 (quarter D1)

PAL

720x576 MPEG-2 (CCIR/ITU-601 D1)
704x576 MPEG-2 (ATSC Table3 D1 is actually a US standard, but...)
352x576 MPEG-1 and MPEG-2 (half D1)
352x288 MPEG-1 and MPEG-2 (quarter D1)

I'd only crop it if I were using the video on a computer display where it would show up because the frame is smaller than the desktop.

Dr. Mordrid

[DarrenD]

Point taken. It's simpler to just leave it alone.

Thanks

[Brian Ellis]

Bingo!

[CaN-o-PuS]

There are times when you have to deal with the black at the left and top, namely in effects like P&P or other 2D/3D effects where the overscan area is not involved.

[Dr Mordrid]

That's what the CROPPING video filter is for. Used in combination with a 2D moving path (often set to a stationary position for PIP's) for scaling purposes it works just fine.

Dr. Mordrid

[Brian Ellis]

I'd bet a pound to a penny that if you showed a clip with the black bit untouched in a PinP insert to a 100 ordinary people and you asked them afterwards whether they saw anything wrong with it, 99.9 of them would say no. Perfectionism is all very well, but let's keep our feet on the ground. As I've always said, it's how the picture is perceived by the viewer on a TV screen that counts, not what us techies think they should perceive when we look at our computer screen.