Disable deinterlacing?

[mlbdude]

So why does the setting of BOBWEAVE 2 make the video look interlaced on a PC monitor? I was under the impression that that did a Force Weave like in Elecard which describes it as no deinterlacing. Back to back they sure look the same.

[gplasky]

Confusing is an understatement.

Ok-so I made the change based on this info:

Hauppauge by default de-interlaces the mpeg stream, which is fine if you plan on viewing it on a non-interlaced display like your pc monitor. If you only plan on viewing it on a tv set you might want to consider using the weave setting. This will allow you to get a proper interlaced picture which gives a higher quality picture on your tv set. You will probably also need to set the overscan settings to 0.

This statement gives me the impression that because it deinterlaces by default (is this true?) that using this setting will actually provide the TV an interlaced picture. Since interlaced is what a TV really wants this will result in a better picture.

Also based on this I would think anyone outputting to a TV would want to do this and would get a better picture.

Just trying to get a better handle on this. Because bottom line, on my TV and with my eyes-the picture appears way better. I really noticed this morning on GMA the scrolling news ticker was super smooth and didn't have that sometime jagged effect or halo/color effect on the lettering.

Gerry

[mlbdude]

According to 100fps Weave deinterlacing does nothing and does not deinterlace. I always thought there was a difference between weave and force weave but apparently not.

So back to the initial question, how to best setup output for TV display? I am concerned with standard def mainly but it looks like others want to know what to do with HDTV.

I have tried not deinterlacing and the output tends to be blurry/ghosting during high motion scenes with some scan lines also visible with some shows, and deinterlacing tends to cause the image to loose some sharpness.

What do we do and how do we do it?

[stanger89]

Gerry,

Your TV is an HDTV, it has a native resolution of 1280x720 progressive. Given this, it "wants" to see an input that is 1280x720 progressive. If you feed it a progressive signal over VGA, you are bypassing TV's deinterlacer. PCs always output progressive signals unless you specifically tell it not to, for instance setting the refresh rate to 30Hz interlaced.

If you have DXVA enabled, changing that registry setting might not have the same effect as it does if you're not using DXVA. It might not have any effect at all, I know Sonic filters have an entirely different set of keys for DXVA and Software modes. Also if you're using DXVA, you're probably using some of the more advanced deinterlacing algorithms built into your video card.

You only want to output interlaced video if you're using a standard analog TV that only accepts 480i, or if you're running an HDTV that only accepts 1080i.

[stanger89]

mlbdude,

Have you tried running your desktop at 720x480 @ 30Hz Interlaced? That might help. My understanding of TV out is that the TV encoder basically scales and interlaces whatever's in the video card's framebuffer (might not be the right term). The problem is that the video starts interlaced (720x480@30Hz interlaced), gets recorded played back to a progressive output, whatever you have video card set to, likely 800x600@60Hz, so now the video is 800x600@60Hz progressive, then it has to scale that back to 720x480, and interlace it for output over S-Video/composite.

By setting your desktop to 720x480 you avoid scaling the video, and if you set the refresh rate to 30Hz interlaced, possibly you can avoid the progressive -> interlace step (although this could cause an interlace-> different interlace problem).

Not sure if that will help or not, but we can hope.

[mlbdude]

I currently run 640x480 but have tried 720x480 as well. I have always run 60Hz and never 30. I thought TV's ran at 59.XXHz anyway?

I will look to try 30 but I don't think my drivers will do that.

Also, setting BOBWEAVE with DXVA enabled still works. The video plays back looking interlaced on my PC. However, once I realized Weave is the same thing as Force Weave you can use Sage to enable Weave and it works fine.

[stanger89]

Actually TVs run 59.94 Fields/sec, which is 29.97Hz (or there abouts).

[gplasky]

OK. I'm starting to get it. And I do have DXVA enabled so this is probably causing it to use the more advanced features of my card giving me a great picture. I'm also outputting via overlay and not VMR.

Still some confusion. So when I record off of TV wouldn't these recordings be considered interlaced? And if so, when I play them back wouldn't they still be interlaced or would they now be a progressive signal? And it's progressive because my video card is set for 1280 x 720 so as far as my TV is concerned it's getting a progressive signal.

I may try to get some screen shots so you can see the difference on my set betwen enabling that setting and not having that setting. To me it looks better. And I'll check it against a fast motion sports screen with lots of movement to see how it plays out. Thanks for the Deinterlace 101 class. I hope it's not too much of a bother for you. I appreciate your time.

Gerry

[stanger89]

Gerry,

Sounds like you've got it. I'm not entirely sure how the 250 encodes the signal it receives, but yes, since you are running a progressive resolution/refresh everything your TV sees is progressive.

And it's not a problem at all, I've been messing with this stuff for a while, I like messing with this stuff (so long as it work when I expect it to), and if I can help somebody out along the way, all the better.

[dadams]

6

[salsbst]

Originally posted by gplasky
I thought this kinda of explained why this setting would make the picture better on any TV:

"Hauppauge by default de-interlaces the mpeg stream, which is fine if you plan on viewing it on a non-interlaced display like your pc monitor. If you only plan on viewing it on a tv set you might want to consider using the weave setting. This will allow you to get a proper interlaced picture which gives a higher quality picture on your tv set. You will probably also need to set the overscan settings to 0."

I thought the MPEG2 was encoded in all its interlaced glory, and that deinterlacing was being handled by the decoders? Maybe I've never understood the WinTV PVR. Does it deinterlace beforce encoding?

And where did that quote appear?

[stanger89]

Yeah, this is complicated isn't it.

Assuming the video is stored interlaced:
My understanding of how decoding works (at least software decoding) is that it always outputs a progressive image, in the case of NTSC it outputs 30 frames per sec (from 60 fields/sec encoded). Weave simply sticks two fields together without any fancy algorithms to make sure those two fields belong together (that's why this can look horrible on a progressive display). But on an interlaced display, this would work well if the video fields line up correctly with the display fields, ie line 1 from video is displayed on line 1 of the display, 2 on 2, etc. In that situation everything would be fine. However if for some reason (your running windows at 800x600 but NTSC is 640x480) then you can run into problems where parts of 1 and 2 from the video can be combined and displayed on line 1 of the TV (since the video had to be scaled to 640x480), this would be why weave can result in poor PQ for some.

Now, one further thing to complicate things:
I'm not entirely sure the 250 encodes video interlaced. The reason that I say this is the encoder is capable of Inverse Telecine (IVTC). Telecine is where 24fps (film) content is converted to 29.97 fps content by adding extra frames. Now from my Dscaler days, I remember a lot of content (aside from commercials) on TV is actually 24fps, so if the 250 is doing IVTC it could cause additional problems for those of you trying to use interlaced displays. Now I don't have anything to back this up but it seems somewhat logical.
http://www.shspvr.com/forum/viewtopi...verse+telecine

Perhaps I'll have to play with this more. FWIW the InverseTelecine key is set to 0 on my system.

[salsbst]

I really don't understand how the 250 could be deinterlacing. If the card were deinterlacing before encoding, then setting deinterlace options for the video decoders would be a little silly. Also, SHS said in http://www.shspvr.com/forum/viewtopic.php?t=2747 :

Far I know of there only one realtime hardware deinterlacing but it not a capture card Holo3DGraph being it only card that support DCDi.
You read about here
http://www.dcdi-video.com/technology...-overview.html

[gplasky]

That quote came from here:

Amontillado's DVCR, PVR, HTPC info

Check out the site.

Gerry

[salsbst]

Thanks, gplasky. There are some neat registry tweaks there.

The text is a bit misleading if not incorrect... he means to say that the intervideo decoder defaults to the bob method of deinterlacing, not that the 250 does any deinterlacing.

[stanger89]

Gerry,

These tricks unfortunately don’t always work, some graphics card’s tv out are just not suitable for it.

There are many variables in interlaced playback (more than progressive) so that's why it doesn't always work.

salsbst,
Like I said, I don't know how the 250 stores the encoded video (probably interlaced) and I'm not sure what IVTC does in this context (I understand it in a Progressive DVD playback context), I threw that in as much for something else to try/consider as anything.

[salsbst]

My main concern was that I not do two rounds of deinterlacing if at all possible. I'm happy again now. Thanks.

[Amontillado]

Originally posted by salsbst
Thanks, gplasky. There are some neat registry tweaks there.

The text is a bit misleading if not incorrect... he means to say that the intervideo decoder defaults to the weave method of deinterlacing, not that the 250 does any deinterlacing.

Yep, that is approximatly what I meant to say, sorry for the confusion (thats what you get if you write the text late at night and don't check it anymore).

Although... the codec doesn't default to weave but to bob, but that is probably what you meant to say

[salsbst]

Whoops... ok, fixed that. Thanks, Amontillado.

[kenb]

i know this is an old thread, but i was browsing for info on interlace control tonight, found this thread and had something to add. i'm using a hauppauge 250 card to record with and i'm displaying the vid on a panosonic elite hdtv (crt type) with an ati all in wonder 8500 through a transcoder...

anyway, i've been trying all sorts of things to eliminate combing in the resulting video. i've tried several different codecs, but unless i paired one up with ffdshow and used its deinterlacing, it still combed. so i took a close look at the video and discovered that if i swap the interlaced fields, it looks fine.

my problem is that i don't have an easy way to do this on my htpc, i looked at the vids on another machine where they combed badly on the crt. using a tool like dvd2avi, i could swap the interlace fields and the combing disappeared.

so, i don't know if the hauppauge encoder is getting the fields backwards, or whether this is a problem with my ati display card. but i thought i'd mention it.

kenb