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Discussion Starter · #1 ·
Hello everyone, I just stumbled upon this forum today, I can't believe I've been trying to built an HTPC without it! :)


I'm trying to set up a PC to act just like a Tivo as a pet project. The problem I'm having is with interlacing artifacts on playback.


I use SnapStream PVS 3.0 Beta to record 640x480 MPEG2 files of TV shows (NTSC), and I play them back on my 36" Sony Wega TV (non-HD). The files are of course interlaced. I figured this wouldn't be an issue since my TV is an interlaced display device, but this doesn't seem to be the case. If I play these MPEG2 files on my TV I can clearly see "combs" or "stairs" when things move quickly, or when panning the camera.


I've tried various software solutions like DScaler and the built-in deinterlacing in SnapStream but it doesn't have that "perfect" look, you can still see blur or grainyness with motion. The only software solution I've gotten to produce decent results is with a few filters in VirtualDub and post-processing the MPEG. This isn't a really usable solution since it takes so long, but I thought I'd mention it. :)


So I figured I'd try a hardware solution. I tried various video cards, cables, I even hacked my XBox to display the video but it still looks poor due to interlacing.


So I'm wondering, how does Tivo do it? Is there something I can buy or hack to get the interlaced videos "in sync" with my TV? I see that a newer video card from Hauppauge has an MPEG Decoder built-in with S-video output. Is that the sort of thing that I'm actually looking for? Maybe there is some software out there that can drive my video card in that way to play back the MPEG2 file as-is?


Thanks for any help on this. I've been trying to get perfect playback for quite a while now. I've learned a lot thats for sure. But this interlacing thing has me stumped... interlaced video, interlaced TV, why can't they work together? :)
 

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personally i havebeen using the 250pvr combined with an xcard. and sagetv or wintvcap as a one touch record device. xcard is hardware mpeg decoder. which if you dont have digital/hdtv connections i belive is currently the best option. i have compered this to the pvr350 and the picture is better. it also reqires little resorses to record or play. wintvcap is good as well as it records in the task bar and runs via command line prompts. check out .
www.shspvr.com lots of tweaks advice etc.

regards
 

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You can use ffdshow in Zoom Player to deinterlace on playback.

How is your TV connected to your PC? Svideo?

What video card do you use?


Regards,


Owen
 

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Discussion Starter · #4 ·
Ahh so you are saying hardware decode is the best way to get an mpeg2 to the TV? You don't see any interlace artifacts on your decoder card when viewing interlaced video files?


I've got an s-video connection to my TV via my GeForce2 MX. I've tried DScaler, I'll try zoomplayer but I doubt it'll do much better. Realtime deinterlacing does a decent job but I watch a lot of cartoons, and when a cartoon pans horizontally everything gets shot to hell. :) Like I said, the only way to get that looking good is to post-process the video in virtual dub and thats not even perfect. I'd love it if I could find some software that would display the movie on the TV like it was supposed to be shown, interlaced.


Thanks for the replies guys I have a few more things to try now.
 

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There's 2 techniques which I've found give great deinterlacing results. The first is, of course, DScaler. Using it with the Elecard MPEG2 Video Decoder filter yields great results, and there's a lot of flexibility with the DScaler plugin.


What I've found works the best is using a video card that has DXVA and utilizing the hardware deinterlacing on the video card. This is dependent upon the MPEG2 decoder you're using and your video card. Personally, this is what I use with Intervideo's decoders when displaying on an interlaced TV. Most recent nVidia and ATI chipsets support DXVA.


SageTV or SageRecorder can make use of either of the above techniques.
 

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It's an option in Setup->Video in SageRecorder or SageTV. You just need to download the MPEG2 Video Decoder from Elecard and install that. Then the DScaler option in Sage becomes available.
 

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Discussion Starter · #8 ·
Hardware deinterlacing on the video card might just be the ticket. I didn't even know video cards supported such things. I'll check it out (I assume I can use the trial version of WinDVD)


I'm still curious how Tivo manages such a perfect picture. Do they have a hardware deinterlacer? Or does it output the interlaced signal to the tv directly?


Actually this makes me wonder, do those microsoft media center PCs use the hardware deinterlacing on the cards they come with? I keep getting conflicting reports from people about the output quality of those machines.


Whew a lot of questions. :) Thanks for all the suggestions.
 

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Maybe the Tivo has such a good picture because it was designed to work with a TV and doesn't deinterlace the signal, so it feeds an interlaced signal to tn interlaced display.


On the computer, the interlaced signal is recorded, then de-interlaced for display on computer monitors, then re-interlaced if you are displaying on a TV. Just a guess.
 

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Discussion Starter · #10 ·
Well I tried WinDVD, with hardware decode enabled and I played with all the deinterlacing options. It did a pretty good job but still has that "deinterlaced in real time" blur to it. I'd say I was able to get better results with DScaler.


I have this one clip of video I play that is a cartoon where the camera is panning from right to left. It really shows off any problems with the deinterlacing. Like I said the only time I was able to tame this beast was with a heavy duty post-process in VirtualDub. :/


About Tivo, I would love to know what its doing for sure. If its something like what you say, where the hardware directly sends the mpeg to the TV then I want to know if I can get this hardware on a PC somehow. :)
 

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Jayzen,

The best solution is not to deinterlace at all.

But getting interlaced video to play back correctly on a TV output is not so easy, as you have found.

There are some rules that must be followed.

You must capture at the correct picture hight 480 for NTSC. Or exactly half that (240). Your doing that right.

Next you must play this back at the same resolution, say 640x480.

This means playing pack at full screen on a 640x480 desktop with the TV output set to 640x480.


Nothing else will work.


I could never get this to work perfectly with older Geforce cards like your GF2MX

Some newer Geforce cards (NOT MX cards) use the new Conexant CX2587x TV out chip.

This works much better in every way, and is highly recommended for a top quality TV out solution.

Some Matrox cards are said to have good interlaced TV out. But I have not used one and cannot comment on how well they work.

Another useful addition is software called TV Tool. It controls the TV out chip and dose a much better job than the Nvidia drivers. Get it.


The capture card can have an effect on this as well. I would recommend one of the newer cards based on the Conexant 2388x chip.


Also you should test capture to an Mjpeg format with Pic Video Mjpec codec to make certain that the Mpeg2 compressor is not causing you grief.


One last problem that sometimes comes up is field order reversal.

This is when the “A†and “B†fields are played in the wrong order. This mostly occurs during capture and is hard to fix.


As you can see. It gets complicated.


A capture card with hardware compression and it own dedicated TV output should just work without issue. And is a high cost but low stress alternative.


Hope all this is helpfull.


Regards,


Owen
 

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Discussion Starter · #12 ·
Thanks Owen that was the info I needed to know! I thought it might be possible to not have to deinterlace the file at all if I had the right hardware, just didn't know which hardware and what settings. :)
 

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I find it hard to believe that the makers of the TV out on VGA cards dont get there act together with this major issue. I have a problem that I have a few captures at 720x576 (PAL) - and _NOTHING_ I have tried will play them back correctly. I have come the closest with a GF2MX card running at something by 576 and the flicker filter off, but its luck of the draw whether the fields will be in the right order or not when playing back.


never thought to try my xcard for playback. It was put into the useless crap box soon after purchase, im not too keen to transcode again into something it will play.
 

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Discussion Starter · #14 ·
As an aside, I never got the playback working. As far as I can tell its not possible to output interlaced video with a VGA card that plays back on an interlaced TV correctly.


I do think that cards with dedicated mpeg2 playback hardware will do it, since that is their design, but almost no software supports this feature so its not all that helpfull. Maybe in the future.
 

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This is an interesting thread. I'm finding myself recording more and more interlaced MPEG2 material from UK terrestrial digital TV using my Nebula Electronics DigiTV PC receiver.


For quality reasons, I've opted to bypass TV-out completely and drive the RGB-S SCART input of the TV directly from the VGA port. This requires the PC to drive a sub-VGA frequency interlaced signal but it's all possible using PowerStrip.
VGA to RGB SCART


The problem is that the PC has been a predominantly non-interlaced environment for ages now, so everyone just seems to assume that you want to deinterlace everything.


Ideally I'd like to make use of the interlaced display mode to play my recorded TV back to my TV in it's native interlaced format, however I haven't managed to do this yet. I really don't know if the player / DirectShow has any idea that it should match the field order of the media to that of the raster scan on the display device. (any programmers out there?) I read somewhere that someone got it working to the point where there was a 50% chance upon playback start that the field order would be correct and that he had to stop and start the video until he was lucky enough to get the phase correct.


My only workaround is to experiment with ffdshow as a postprocessing deinterlacer after the Elecard MPEG2 Decoder. Results haven't been that special. 'realtime deinterlacing mush' is a problem, just as a previous poster described.


some good interlacing / deinterlacing articles...
What is Deinterlacing? Facts, solutions, examples.
NTSC, PAL & Interlace Explained
 

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A hardware decoder with it's own S-video out should do the job. Gotta make sure the field order on your video is correct though like one chap above mentioned.


If your TV has a YPbPr input, you might even be able to use an HDTV tuner card like MyHD to play your video (converting to VOB or transport stream with TMPGenc, if .mpg doesn't work). Specs on MDP-120 at least indicate 480i support. Kind of a costly solution though just for your own video. :)


Another possibility is the YPbPr component adapter from ATI which supports 480i. Anyone tried interlaced playback of DVDs or captured video with this puppy?
 

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Jayzen,


I have also been looking for a way to view my interlaced AVI and MPEG2

files on my TV without deinterlacing.


So far, the best I can do is use TVTool to turn off the flicker filter in my

ABIT geForce2 MX video card with TV out. The flicker filter blurs two

fields together. Without the filter, 2 fields show on the TV in rapid

succession.


There are 2 problems with this.


First, pausing on a frame with high motion in it causes the TV display to

oscillate quickly between the 2 fields. Looking at that gives me a

headache, just like working under a cheap fluorescent light that fails to

blend the 60 light pulses per second together.


Second, the field order has to be correct in the video file, or high motion

portions of the video will appear to shake side to side. When you play

those portions frame by frame, the actor takes 2 steps forward and one

step back. The flicker filter gets around that shaking by blending field

pairs together instead of showing them one after the other.


If the field order is backwards, then I have to use VirtualDub/AVISynth

with the ComplementParity command to reverse the order. And since I'm

in Vdub anyway, I go ahead and use separateFields to give me 60

frames per second where each frame is a single field. I play this in

ZoomPlayer with Aspect Ratio set to fit-to-screen, and the sharpness is OK.


Since separating fields and reversing field order are simple, quick

processes, a filter that does these 2 steps ought to play under ZoomPlayer

in real time. I haven't found such a filter yet, though. When I do, then

I can skip the VirtualDub/AVISynth step, which renders slowly at about

10 fps.


Let us know if you find a better way. There are discussions about

using PowerStrip to create resolutions like 1440x960i and viewing

interlaced MPEGs under that, but I haven't experimented with that yet.


--tater
 

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Discussion Starter · #19 ·
Wow so you actually got it working? What resolution do you use on your TV to display the files?
 

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Hello :)


I have a Sigma Designs HOLLYWOOD PLUS card. This PCI card can only output mpeg1 and mpeg2 but the quality of the image is as good if not better than a low to medium priced DVD player. You also don't have the many issues you have with TV out such as screen size/position and flicker control and blah blah blah. I use my ATI RADEON 7500 to output DivX and Xvid to my TV but I always use my HOLLYWOOD PLUS to output mpeg1 and mpeg2.


Anyways, the HOLLYWOOD PLUS card (sometimes called the RealMagic Hollywood Plus) is now an old product and the replacement is the RealMagic XCARD. Whereas the Hollywood Plus only had a 480i composite/S-Video output the XCARD supports 480p output via component out (the card comes with composite and S-Video out standard I think for component out you need an additional adapter ... but I'm not positive about that since I don't own one). The card can even scale up to HDTV resolution but not with a copy protected source. But of course no A/V capture will have copy protection and as for playing back a DVD you can always rip it to the HDD first using DVD DECRYPTER in file mode (edit --> select all files) and have protection free playback that way.


In any event, the Hollywood Plus (and the new XCARD which works about the same) are the best way of outputting mpeg1/mpeg2 video from a computer to a television. Also note that the XCARD supports DivX out as well though you have to encode without any of the PRO features (such as GMC and QPEL) selected for proper playback.


RELATED LINKS:
Sigma Designs for the XCARD
Doom9 website for DVD DECRYPTER
 
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