G450 eTV YUY2 field order problem

[junkmalle]

Has anyone else noticed that the G450 eTV captures YUY2 with some sort of field problem? The field order appears to be reversed, although it may not be that simple. I created a test video with single pixel thick nearly horizontal lines on a DVD. I then recorded that video with my DV camcorder and with several capture programs using the eTV in YUY2 mode. Here is a crop of the results:

[IMG]c:\temp\crops.jpg[/IMG]

The top three lines are from the eTV card, the bottom three from the DV camcorder.

Has anybody else had this problem? Anyone have a fix?

Thanks.

[junkmalle]

Well crap, how do I attach an jpg image?

[IMG]crops.jpg[/IMG]

[Brian Ellis]

I take it you used field order B throughout when capturing with G-450 and field order A when usinf the DV?

[junkmalle]

Brian,

I take it you used field order B throughout when capturing with G-450 and field order A when usinf the DV?

That was my first thought but the problem appears to be more subtle. When I capture to a YUY2 AVI file none of the software gives option for the field order. You would think that the Matrox's PC-VCR option, regardless of which field order it is using, would correctly play back the files it creates. It doesn't.

I've tried a overriding the default field order of the input (YUY2) file in two applications, Ulead Media Studio 6, and TMPGENC Plus 2.5. And the problem only gets worse!

I believe that the fields are shifted by one field. Consider the following 8 scan lines numbered 1 through 10.

1
2
3
4
5
6
7
8

If they were saved in one field order but played back in the opposite field order, pairs of odd and even scan lines would be reversed.

2
1
4
3
6
5
8
7

You could fix this simply by reversing the field order.

But what if the field order was wrong and the first scan line was missing (2 in this case)? When you swap the remaining lines you get:

4
1
6
3
8
5
10
7

Instead of fixing the problem it has gotten worse! I believe somthing like this is happening. That is, the YUY2 file created from the eTV card is missing a scanline.

I did some more experiments and found something even wilder.

I created an image of alternating, single pixel, horizontal black and white scan lines. The left part of the image started with white on scan line 1, and part of it started with black:

WWWWBBBB
BBBBWWWW
WWWWBBBB
BBBBWWWW
WWWWBBBB
BBBBWWWW

This image was put onto a DVD. WHen played back on a TV this flickers like you wouldn't believe! Actually you probably would believe. The left half of the image is white on one field and black on the other. The right half of the image is the oppsite. But over a full frame the full image is there.

Using the PC-VCR application, I saved in YUY2 mode. The frames show the same weird interlace problem as my image above. But there were both black and white lines on both sides of the image.

But when I recorded in 704x480 MPG SP mode the left half of the image was ALL white, and the right was ALL black! There was also some large text on the screen and this appeared normal albeit a little fuzzy. The conclusion? PC-VCR capture a single field and created the second field by interpolating pairs of lines from the first field! The same thing happened at 352x480 and 352x240. Captures with Ulead Media Studio 6 showed the same thing.

I always thought the MPG output from the eTV was a little soft. Now I know why!

[junkmalle]

I thought it might help if I posted the images I used. Here's a JPG of the image with alternating black and white horizontal lines. The original was BMP but the JPG is pretty clean.

I'm not sure if I can attach two files so I'll attach the results from PC-VCR in another message.

[junkmalle]

And here's JPG extracted from the PC-VCR MPEG file.

[junkmalle]

I might also mention that the image in PC-VCR's monitor window while capturing looks to be correct. It flickers a lot (as expected) but you do see all the scan lines.

I don't suppose there's any hope of Matrox fixing this since it looks like the eTV series is being end-of-lifed. They have't released the source code for the card's drivers or the PC-VCR app have they?

[junkmalle]

Well, I found a workaround for the field order problem when recording in YUY2 mode:

If I record YUY2 with a program called AVI_IO, and use either the HuffYUV or PicVideo MJPEG codecs, the resulting AVI files playback fine with Media Player and Real Player, even Matrox's PC VCR.

But the files still didn't work right with Ulead's Media Studio Pro 7 and other editing programs. A little digging turned up options in both those codecs to "swap fields on decompress". Enabling this option resulted in proper playback and editing everywhere.

Some links for anyone who needs them:

AVI_IO: http://www.nct.ch/

PICVIDEO: http://www.jpg.com/

HUFFYUV: http://neuron2.net/www.math.berkeley...g/huffyuv.html