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| DVD record deinterlace http://forum.linhes.org/viewtopic.php?f=6&t=13848 |
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| Author: | ErikU [ Fri Jan 26, 2007 3:42 am ] |
| Post subject: | DVD record deinterlace |
Today I created my first DVD from a couple HD broadcast records. When viewed on a regular set to box, there are big interlacing problems. It's as if the material is converted to progressive without de-interlacing. Converting to progressive is totally unnecessary when making a NTSC DVD! How do I change the deinterlace options for DVD recording? |
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| Author: | marc.aronson [ Fri Jan 26, 2007 8:37 am ] |
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I've never tried to create a DVD from an HD recording , so I can't speak from experience on this topic, but I will make the following observation: Some HD signals are 720p (1280x720 progressive scan) and some are 1080i (1920x1080 interlaced). If the HD channel you recorded is 720p, then the problem is not that someone de-interlaced the source video -- the problem is that you need to interlace your progressive scan material to play it properly on an interlaced display device. Of course, some DVD players have this capability built in. If memory serves me correctly, FOX & ABC both transmit 720p. Marc |
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| Author: | ErikU [ Fri Jan 26, 2007 2:57 pm ] |
| Post subject: | |
Nope, this is 1080i stuff. Both video originated (true 1080i) and film originated (was 24p with pull-down added to make it 1080i for distribution and broadcast) have the issue. It should all be left alone and not touched at all when going to DVD. 1080i (video or film) and 720p. Where can I make the adjustments? |
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| Author: | crabby [ Sat Jan 27, 2007 8:13 pm ] |
| Post subject: | |
But DVD video is 480 lines. The 1080 source has to be scaled down to conform to the DVD specs, it can't remain untouched. My guess is part of your problem comes from scaling the video but I'm not sure. |
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| Author: | ErikU [ Sat Jan 27, 2007 9:03 pm ] |
| Post subject: | |
True, it does need to scale, but it *should* do so in the vertical by simply throwing out lines. Downconverting is pretty basic, and there should be anything done to affect interlace. |
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| Author: | turpie [ Sun Jan 28, 2007 2:28 am ] |
| Post subject: | |
ErikU wrote: True, it does need to scale, but it *should* do so in the vertical by simply throwing out lines. Downconverting is pretty basic, and there should be anything done to affect interlace.
How could it know which lines to throw out? If you throw out every second line you still end up with 540 lines which is more than 480. The best option would be for it to deinterlace before scaling. Is it possible to do deinterlacing from the command line? |
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| Author: | marc.aronson [ Sun Jan 28, 2007 9:18 am ] |
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turpie, there are many approaches to scaling and deinterlacing video using the software that comes install with Knoppmyth. How are you creating the mpeg2 stream that is being burnt to the DVD? Mencoder? VLC? Something else? A bit more info on how you are doing this might help us help you. Marc |
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| Author: | ErikU [ Sun Jan 28, 2007 5:02 pm ] |
| Post subject: | |
Actually 540 is the correct number of lines when downconverting. The extra lines are the VBI and get thrown out. So it really should just throw out the even or odd lines,.. as simple as that. If it were progressive source, it should just throw out every other line. There should be no other processing to the vertical resolution. It takes very little processor power to downconvert like this. I was the one with the original question. My source material is HD off air. Some of it 1080i video source, and some originally shot 24p and converted to 1080i with pulldown for broadcast. This is what I am trying to make a DVD from and the DVD has bad interlacing problems... which it shouldn't. Thoughts? |
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| Author: | marc.aronson [ Sun Jan 28, 2007 6:40 pm ] |
| Post subject: | |
ErikU: Let me ask my question again. The NTSC standard for DVD's says that the mpeg streams have to be one of the standard resolutions to successfully play them back on a consumer set top DVD player. Those standard resolutions include 720x480, 352x480, 480x480 and a few others. I do not believe the standards include anything with more than 480 scan lines. As you've said, your source material is 1920x1080 interlace. I am assuming you are running your 1920x1080 interlaced mpeg file through some sort of utility to convert it to a standard NTSC resolution. Is this correct? If so, what utility are you using? If you're not doing anything to convert your 1920x1080 interlaced source material to a standard NTSC resolution, I don't see how you will be able to get it to play back on a standard, consumer DVD set top DVD player. Marc |
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| Author: | Liv2Cod [ Sun Jan 28, 2007 7:48 pm ] |
| Post subject: | |
ErikU wrote: Actually 540 is the correct number of lines when downconverting. The extra lines are the VBI and get thrown out. So it really should just throw out the even or odd lines,.. as simple as that.
At one time I agreed with you. I have learned, tho, that the only way to convert from HD to DVD resolution is to basically decode and re-encode the video. You're going from a video resolution that is 1920x1080i (with square pixels) to 720x480 (which has rectangular pixels). Unfortunately, there is no shortcut. Not yet, at least. P.S. The VBI isn't involved here, since the HD signal contains 1080 lines of actual picture information. You would lose the top and bottom of your picture if you just converted it to 540 lines and then threw away 60 lines to make it 480. |
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| Author: | ErikU [ Fri Feb 16, 2007 11:35 pm ] |
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Good point on the VBI. But yes, I can make NTSC DVD's in myth from HD recordings that play in a set top player. It works great, and they look great, except for major interlacing problems in motion. There must be a fix for this? |
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| Author: | alien [ Mon Feb 19, 2007 3:22 am ] |
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I've had problems where ffmpeg (used by mytharchive) doesn't guess whether the source is interlaced or deinterlaced correctly. There is an option that can force it. I'm not at my box, but "man ffmpeg" to find it. For mytharchive, there is a profile for the ffmpeg options in /usr/share/mythtv/mytharchive/profiles/ directory. I think you can just add the nodeinterlace option. Don't forget to take it back out before you try burning interlaced source. Actually, now that I think about it you might need to use the deinterlace option. Yes, the change is only resolution, but transcoding an interlaced stream without deinterlacing just causes problems sometimes. That's why it is almost impossible to view an interlaced mpeg stream with myth on an interlaced SDTV without deinterlacing. Allen |
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