1080i to 720p x264 (why do i want to deinterlace)

[d-wil]

I used the guide (entitled HDTV TS to HD H264,XviD) I found on this website which links to
http://nwgat.net/guides.htm
but my question is why do I want to deinterlace? I have always heard that if the source is interlaced then I should stay interlaced. I followed the guide and used Megui. When running through the x264 configuration I found no Preserve Interlace option like in DivX or Xvid configuration. Does that mean that x264 will preserve interlace if the source is interlaced?

Also in the avs script I used from the guide there is a function
tfm().tdecimate()
is this what deinterlaces and if I remove it my final video should be interlaced? I just want the output video to be the best quality possible.

[jagabo]

1080i to 720p... why do I want to deinterlace?

Because 720p is not interlaced.

tfm().tdecimate()

That is an inverse telecine. If your source is telecined film you can use that to restore the original 24 fps progressive frames -- your best option in that case.

[manono]

Hi-

but my question is why do I want to deinterlace?

Performing an IVTC isn't the same as deinterlacing. Deinterlacing will make it progressive again, but either create one duplicate frame in every 5, or create 2 blended frames in every 5, depending on the deinterlacer used. IVTC (in this case, the TFM/TDecimate combination), if it can be used, will make it progressive again by field matching and removing the duplicate frame. When possible, you want to IVTC.

If you're converting to 720p, you'll have to make it progressive one way or another. XviDs are usually progressive also, so keeping it interlaced isn't usually an option anyway.

[d-wil]

But the source is interlaced (1080i). I have found a good deal of information about deinterlacing 1080i and I do not know why anyone would want to do this.

[manono]

I have found a good deal of information about deinterlacing 1080i and I do not know why anyone would want to do this.

Then you've either read the wrong information, or you haven't absorbed what you've read.

[d-wil]

Maybe I was unclear, I dont give a rat's a$$ if it is 720p or whatever. I just want to convert my 1080i video files to a manageable file size (40 min = 1Gb) while maintaining quality. I figure using x264 is the best way to do that.

[FulciLives]

You are confusing the terms DEINTERLACE and IVTC (Inverse Telecine).

Two completely different ways to make an INTERLACED source PROGRESSIVE.

If you can do an IVTC (which often is the case with 1080i or at least that is my understanding) then that is A-OK to do.

DEINTERLACING is generally speaking NOT a good idea but sometimes it cannot be avoided depending on the source and what you want to do with it.

I wish I had a good website reference handy to explain the two but I do not. Perhaps manono does (he seems good at pulling out such links LOL)

In short the two methods are completely different and doing an IVTC is good whereas DEINTERLACING is bad. Some sources can be IVTC'ed but some cannot ... which is when you DEINTERLACE ... if you need to make the source PROGRESSIVE.

- John "FulciLives" Coleman

[manono]

I just want to convert my 1080i video files to a manageable file size (40 min = 1Gb) while maintaining quality.

Maybe look at it this way, then. 1080i is 29.97fps. If the source is a movie or TV show shot on film, the base framerate - the original framerate - is 23.976fps. Film (like the stuff you watch in a movie theater) is 24fps. By encoding at 29.97fps you're encoding 25% more frames unnecessarily. If you're also keeping it interlaced, 40% of the frames (2 in 5) are interlaced, and interlacing requires many more bits to maintain the same quality as it doesn't compress nearly as well as do progressive frames. Therefore, by reducing it to 23.976fps via an IVTC, not only will it play more smoothly because you've removed the duplicate frames, but it will have a much higher quality for the same file size, because you're encoding 20% fewer frames, and the available bits are spread around 20% fewer frames. The guide is right. jagabo is right. FulciLives is right. I'm right. You're wrong.

I dont give a rat's a$$ if it is 720p or whatever.

You gave the thread its name, not I.

[FulciLives]

This may not be the "best" solution but since you seem a bit clueless I suggest you try HDTV2DVD which is a program that accepts a HDTV TS stream and outputs a MPEG-2 DVD Video compliant MPEG file complete with a DVD menu and ready-to-burn. It also creates the MPEG file for you (in a separate folder) so you can delete the VIDEO_TS folder and use the MPEG file with your own DVD Authoring software rather than go with the plain jane menu that the program creates.

I tried it on 2 sample HDTV TS files (I am currently testing a new HDTV capture card on my computer) and it worked A-OK ... but both files were 1080i and it does appear that the program DEINTERLACED instead of doing an IVTC. The tests were new "Prime Time" TV shows that I would think are IVTC capable.

So not the best way but it works with little to no knowledge from the person using it. That sounds like a key point in this situation.

- John "FulciLives" Coleman

[edDV]

I just want to convert my 1080i video files to a manageable file size (40 min = 1Gb) while maintaining quality. I figure using x264 is the best way to do that.

40min 1GB is a stretch for SD let alone 1080i

1080i is a tough case for compression below the 14-19 Mb/s MPeg2-TS that I suppose you are starting from. IVTC to 1920x1080p 23.976 may be possible and taking that down to 6-8Mb/s is a stretch but won't be high quality. If you downconvert to 720x480 2-3 Mb/s may yield adequate 480p results.

Maintaining interlace at high MPeg4 AVC compression is a goal but not ready for prime time. VC-1 and to a less extent h.264 have interlace support as a goal but current bitrates are high.