Weird horizontal streaks

[SansGrip]

I'd be grateful for suggestions as to the cause of the "horizontal streaks" (clearly visible at 150% zoom and above) in the attached image. The only processing done to it was to increase the brightness slightly (for proper display on a monitor) and a conversion to RGB. It was captured (AIW Radeon 7500, composite input through VS-8000 video stabilizer) at 29.97 fps 640x480 YUY2 PicVideo MJPEG Q18 from VHS using VirtualDub with cropping to remove letterboxes.

It almost looks like an interlace issue, but the source is telecined and this shot is one of the progressive frames.

Could this be caused by MJPEG? The only such artifacts I've ever seen have been "mosquito noise" in high frequency areas, which doesn't apply to this frame.

It looks like I'm going to have to recapture, but I'd like to nail down the cause before doing so.

Any input would be very much appreciated.

EDIT: I'm using a loaned monitor while I wait for a replacement for mine which broke yesterday, and I forgot to recalibrate :rolleyes:. The previous attachment was too dark. I've uploaded a corrected one.

[jggimi]

I can't see the trouble, as your .png link looks like a black box, to me.

You might try running it through AviSynth with SeparateFields(), to determine if your problem exists at the field or frame level.

[SansGrip]

jggimi: I can't see the trouble, as your .png link looks like a black box, to me.

It is a black box ;)

I picked it because a black frame is where the streaking is most visible. It's very dark because I captured for display on a TV, which obviously has a very different brightness level to a properly calibrated monitor.

Try jacking up the brightness and zooming to 200% or more. The streaks are there, you just can't see them right now ;)

As for the field/frame question: the streaks are still there when I SeparateFields().SelectXxx().

Thanks for the quick response.

[-h]

Wow. Definitely looks like interlaced-DCT artifacts, which MJPEG would've used by default at that resolution. It looks very much like 2 distinct fields.

You could try a highpass cutoff of 16 for luminance I guess, does this only occur with dark content?

-h

[SansGrip]

-h: Wow. Definitely looks like interlaced-DCT artifacts, which MJPEG would've used by default at that resolution. It looks very much like 2 distinct fields.

It sure does. I can't think of an explanation for it. Could this be a bug in the codec? At quality=18 there shouldn't be artifacts like this. Another thought: I was cropping vertically from 480 to 266 during capture. I figured keeping the height even wouldn't cause field problems, but maybe I was wrong?

I notice the codec configuration dialog has an option called "2 Fields If More Than xxx Lines" which is currently checked and set at 240. Perhaps unchecking this would help.

Here's another thought: this is telecined source material, and in all probability the capture driver is just weaving the fields together without regard for pulldown. Presumably MJPEG is then reseparating the frames to encode interlaced. That should just result in the same messed up 3:2 pattern, right? Or is the card supplying separate fields and MJPEG is then reseparating those fields to encode...?

I'm too tired to properly think of the implications of that.

-h: You could try a highpass cutoff of 16 for luminance I guess, does this only occur with dark content?

Unfortunately they're all over the place regardless of luma. They're just a bit more visible in dark areas. I guess this is what was causing the real bad MPEG-1 blocks, huh? ;)

Looks like a recapture is in order. Perhaps I should clear some more space and just use Huffy (it's a 2 1/2 hour movie, which is why I was using MJPEG in the first place).

It's strange, though, because I've done four or five captures with this card and codec, both from VHS and from TV, and this is the only one that exhibits such artifacts - unless I've just not noticed it with the others. I'll experiment tomorrow.

Any thoughts would be appreciated.

[Didée]

After throwing some light into the 'black box',

I see the exact reason why I stepped from using Pcivideo MJPEG @ q18 to q19 + increased color quality from 3 to 2 ages ago.
The former results in a compression of "2*Huffyuv", and this turns out to be the lowest quality I'm willing to accept from this codec.

Sidenote:
For me, these MJPEG-errors are especially annoying when trying to erase alpha-blended logos. With Huffyuv encodes, this succeds astonishing good, using 'delogo v1.3' for Virualdub. With Picvideo@18, the removal is not really usuable. Picvideo@19 is much better, but far away from Huffyuv (of course).

(And I really HATE logos...)

[Ookami]

Originally posted by SansGrip
I notice the codec configuration dialog has an option called "2 Fields If More Than xxx Lines" which is currently checked and set at 240. Perhaps unchecking this would help.

With such high Quality settings this is not useful. Disable it. Also, if you're in a PAL country you should change the 240 to 288 :) . This settings, supposedly, increases the picture quality (at loss to some compressibility) for lower Q settings, but, I'm telling you hearsay, because I only use Picvideo at 19, because it doesn't make much a difference to me (when lossy, then at least Picvideo at 19).

And please, always tell WHAT MJPEG codec you're using. MJPEG is not = MJPEG! If you have a faster system (mine is not fast enough), use the latest Morgan or the Leadtools MJPEG codecs, they give you better quality than the Picvideo codecs (this is not hearsay ;) ).

Cheers,

Mijo.

[SansGrip]

Picvideo@19 is much better, but far away from Huffyuv (of course).

I do use Huffy for shorter stuff (TV caps etc.) but this movie was 2 1/2 hours long and I didn't have the disk space. I think what I might do is just capture TV shows until I get a new HD ;)

[SansGrip]

Ookami: Also, if you're in a PAL country you should change the 240 to 288 :)

Nope, NTSC here in Canada.

And please, always tell WHAT MJPEG codec you're using.

I did - PicVideo :)

If you have a faster system (mine is not fast enough), use the latest Morgan or the Leadtools MJPEG codecs, they give you better quality than the Picvideo codecs (this is not hearsay ;) ).

PicVideo was the only one I came across, but I'll take a look for these two and give them a try. Thanks for the info :)

[SansGrip]

I did some capture tests today and found something disturbing: the artifacts are present even when using Huffy.

In the image the leftmost grab is the output of FieldDeinterlace(), the middle grab of SelectEven(), and the rightmost of SelectOdd(). I used Photoshop to cut out a 100x100 section (100x50 for the separate fields, resized to 100x100) and blew them up to 300x300.

As you can see, the even and odd fields are different enough to cause this weird streaking when they're interlaced back together. This isn't normal... right?

This capture was done from the coax input, but the same thing occurs on the composite input.

I even tried capturing the blue screen my VCR produces, and the same artifacts are present.

I'm using the latest ATI drivers. Is my card broken?

The image is available at http://www.jungleweb.net/~sansgrip/tvcap.png.

[Ookami]

@SansGrip

My comments were more of the general nature and not always directed to you.

If every member would describe his problems like you, it would be much easier to solve them. Thanks :) .

BTW, I'll would move this anyway to the capture forum, but lately I'm a behind with the moving of the threads.

Do you have something against it if we delete your second (new) thread?

Cheers,

Mijo.

[SansGrip]

If every member would describe his problems like you, it would be much easier to solve them. Thanks :) .

I have long experience trying to answer stuff like "I've got a problem with this, it doesn't work. Any advice?" so I try to be as verbose as possible ;)

Do you have something against it if we delete your second (new) thread?

Not at all. I tried to find a way to move it myself, but couldn't. And it wouldn't let me delete my thread in General Discussion ;)

(Incidentally, I wanted to add an attachment to an existing message but couldn't see how, so I think I'll just leave the link in there instead.)

If anyone has any ideas on this I'd be very grateful to hear them, because I'm at a loss.

[ronnylov]

I also get horisontal lines in my TV captures. I have a ATI AIW Radeon card and captures to huffyuv with AVI_IO.

I found the reason to be a chroma noise that is typical in PAL captures, perhaps it is similar in NTSC? I "solved" the problem with an avisynth script. First I tried the avisynth antiblink filter but I got some ghosting at scene changes. Then I tried the Virtualdub filter rmPAL but it did not remove the lines completely. So I made my own avisynth script which decreases the chroma vertical resolution to half but also remove the ugly lines. It seems that the eye is not sensitive to the lower chroma resolution so I'm happy with this solution!

See my posting in this thread:
http://forum.doom9.org/showthread.php?s=&threadid=33319&pagenumber=3

[SansGrip]

ronnylov: So I made my own avisynth script which decreases the chroma vertical resolution to half but also remove the ugly lines.

That's an ingenious solution to your problem... Unfortunately it doesn't work with mine ;)

I can resize the chroma down to 10x10 and back to it's original resolution and the lines are still there. The lines vary more in brightness, not so much in tint.

I'm getting to the point where I'm gonna do one of my complain-politely-but-persistently-until-the-exhausted-store-manager-gives-me-a-refund acts with this card. I've read nothing but bad things about AIW's (it seems that I found all the good articles before I bought it, and all the bad ones after). It's a shame, because the graphics card side of it is very nice. If they could get their act together with the capture/drivers in general they'd have a killer card.

Thanks for the input, I appreciate it. I'll keep searching for answers to this problem while keeping an eye on what people recommend as far as standalone capture cards go...

[Ah, I might as well attach that other, clearer image since I'm posting again.]

[cedocida]

Hi,

I had similar problems because of bad TV-signals and have written a Virtualdub-Filter which tries to eliminate this flickering for both components, chroma and luma. Maybe this is also helpful for you.

2d_comb: here (http://www-user.rhrk.uni-kl.de/~dittrich/filter)

Regards,
Andreas

[SansGrip]

A. Dittrich: I had similar problems because of bad TV-signals

This was my initial thought, but it cannot be the case because it happens capturing from VHS over the composite inputs too..

[SansGrip]

Incidentally, through very brief experiments I've found that TomsMoComp seems to alleviates the problem somewhat (not totally, but a little). It's better than FieldDeinterlace(), but unfortunately doesn't help with telecined material...