Interlace hell. Experts only.

[oddball]

Hi. I have a problem and don't really know a way around it.

I have a Hauppauge DEC 2000-t which lets me recieve Freeview digital terrestrial channels in the UK. The thing about this box is that it lets you record the RAW MPEG2 stream to hard disk via a USB connection.

My problem is this. I think interlace embedded in the MPEG2 file is causing me to see field doubling.

It's UK PAL @ 25FPS 720x576 res.

When viewing the MPEG2 signal via SCART from the box to my 100Hz widescreen TV I don't see any interlace or field doubling.

But when viewing the recorded MPEG2 file via S-Video out on the PC I see something similar to the image below.

http://www.oddball.nildram.co.uk/bscap0005.jpg

Which is distracting on the eye.

I had a look at what Donald Graft's Advanced deinterlace filter 2.6 in VirtualDubMod and it seems to help get rid of some of the frame doubling but tends to make edges of things look rather ugly. If I was converting to DiVX etc I would probably have to use this method but it's not 100% satisfactory. Also for just viewing the MPEG2 files as they are I am stuck. I have tried using WinDVD in the hope that the BOB filter would stop the problem but I don't think when it plays the raw MPEG2 files it uses it. I think it only kicks in the BOB filter when playing back DVD's, SVCD's or VOB's???

A bit of a dillema as you can see.

Can someone explain what is going on here and what methods I might try to get around it?

Big thanks to the techies out there :)

[bb]

Just an idea: have you tried converting the MPEG-2 stream, which is probably a transport stream, by PVAstrumento or ds.jar? Maybe it's just a playback problem as WinDVD expects a program stream.

bb

[scharfis_brain]

looks like a conversion from NTSC to PAL.
many standards conversions are blending fields together.
So there is IMO no good way, to get rid of the blending.

[Kika]

I think, scharfi is right. But to be sure, we do need an original Screenshot without any resizing/filtering. Pictures like this one can be the Result of resizing from 720x576 to 352x288 or of usinge Deinterlacing-Methodes like Bob or Blend.

[oddball]

OK here is a non-resized cap in VirtualDubMod along with a cap of the file info window so you can see it is 25FPS as well as the formats used in the file.

http://www.oddball.nildram.co.uk/mpeg2cap.jpg
http://www.oddball.nildram.co.uk/mpeg2inf.jpg

As you can see it's definitely interlacing. But how can I remove it from a 25FPS MPEG2 source? Preferably in realtime playback or a way to convert it without recompressing. If I was to convert it to a DVD and burn to DVD-R would it playback without the interlace for instance?

EDIT: Just tried converting it to a DVD VOB and played the test image using WinDVD with BOB etc on. Did not make any difference to the image. It still field doubles badly. :/

[fellaw]

This looks like 24fps film --> Telecine to NTSC --> resampled to 25 fps PAL footage. It's not possible to remove the blending, because it's already part of each field. At least I don't know a method which does this. Best would be to encode it interlaced to DVD MPEG2 and author a DVD. DVDs support interlaced MPEG2. After burning, try playing it on a standalone DVD. On a PC, you'll always have the ghost effect, because of the BOB. A TV wouldn't deinterlace the video.

[oddball]

What I will do is try encoding to a SVCD as is (Only resized of course so it should retain the interlacing as it stands). I tried deinterlacing in TMPGEnc and re-encoding to DVD MPEG2 and it looked great. But then I tried to remux the MP2 audio and it was out of sync with the video :(

Re-encoding is NOT what I want to do anyhow. But if the SVCD plays back OK on a stand alone DVD player it answers part of my question in that the hardware does something to the MPEG" stream output in order to display it correctly. If this is the case. Is there no way to get it to do the same type of output conversion on a PC TV out?

It all seems a bit peculiar to me.

One thing of note that makes me think the box is doing something odd is that when previewing the live feed on the PC the audio is playing slower (The pitch is lower) than the feed to the TV SCART output. Which may tally with your theory that it's doing an NTSC to PAL conversion during capture (This is very very bad and I will contact Hauppauge on monday about this if this is the case. It's screwing it up).

I can literally switch between the TV audio and the PC audio for the same channel feed and immediately the audio is playing back at the wrong speed (Probably 4% slower tallying with NTSC 23.976 from PAL 25).

[Mug Funky]

hmm. this may not be an NTSC conversion as such, but i've seen native PAL telecines that are mondo messed up.

i suspect a lot of old VHS tapes and some DVDs are actually telecined by simply pointing a decent quality video camera at a projected film going at 24fps.

my copy of Ghost in the Shell is particularly bad this way.i could clean it up with telecide, but the blending (and any bad interlace artifacts left over) will remain. :'(

[oddball]

Just to put things straight. The Hauppauge DEC 2000-t 'apparently' does no encoding whatsoever but just captures the MPEG2 stream direct to hard disk. The box is a 'Freeview' digital terrestrial reciever for the UK and Germany. It recieves digital signals via a standa terrestrial aerial and converts the data to PAL MPEG2 TS output (PVA). You have to run PVAinstrumento to losslessly convert it to MPEG2 PS so it can be fiddled with correctly on a PC.

So. I think some of the theories just went out of the window if this is the case and the interlace is in the source MPEG2 stream itself. When viewed via SCART output to TV you do not see the interlace. When you playback the MPEG2 stream from a PC you apparently do. I did the SVCD test and it was interlaced on playback still on the PC. But when I viewed the same SVCD directly from a stand alone DVD player via SCART to TV output the interlace went away.

So I go back to my question. Is there a way to do what The Hauppauge box and stand alone DVD player are doing via SCART to TV out, but using TV out on the PC? If not then can someone explain why it's not possible (Throw me some technobabble if you need to).

[Kika]

You don't see the interlacing on the TV, played with the Stand-Alone becaus there are WORKING interlaced. Most of the TV-Outs from Graphics Cards and the PC-Monitor are only working with progressive Frames. If you try to play an interlaced Video over TV-Out without deinterlacing, you will see the interlacing on the TV.
I have only seen one Graphic-Card with a proper interlaced Output. It was a Matrox-Card with a new Beta-Driver. I don't know if this card is available now on market.

[dar1us]

I have discussed/tried to resolve problems that create blending NO MATTER which way you deinterlace. This is involving NTSC>PAL cartoons only as far as I can see.

http://forum.doom9.org/showthread.php?s=&threadid=57206&highlight=Family+Guy seemed to go dead very quickly. Guess noone is smart enough eh':). I think this discusses the problem as displayed by your frame of Arthur off CBBC:D.

When someone comes up with an answer for this problem, be sure to tell me!


harrison

[oddball]

Have you given kerneldeint120 a shot? Probably the smoothest deinterlacer I have seen yet. Reduces the artifacts and nasty rouch edges of deinterlaced material a lot. But only for encoding. My probelm is for actual playback I can find not 'on-the-fly' deinterlacer that gets rid of the blending (Only combing). Most of the MPEG2 decoders like WinDVD, Elecard etc use BOB or weave and nothing like the methods used for encoding.

[scharfis_brain]

as darius said: You cannot get rid of the blendings!
the bob mothode of your MPEG-Decoders produces a 50fps output,which is similar to the TV-output. Because of this your eye can't se the blendings because they occur only 1/50sec.
If you deinterlace the blendings may be shown MORE than 1/25 sec.

Give dgbob a chance if you want to minimise the visible blends (or better said: If your want to trick your eye).
this will broduce a 50fps output better than a pure bob.

[oddball]

How can I use dgbob?

[oddball]

dgbob only works as an Avisynth filter. I need a realtime playback filter. If tools like kerneldeint can do it during encoding. Then there must be a method for doing the same as a realtime playback filter. I'm not convinced otherwise.

[scharfis_brain]

Then there must be a method for doing the same as a realtime playback filter.
DGBob does so!
Even better!

It just produces 50fps video.