Interlace anomaly

[Your_Idol]

When I encode a video with the “preserve interlace” setting, a strange thing happens. The top field is fine but the bottom field has some colours removed and other colours added like a ghosting affect from the top field.

I have included a picture of a frame with the fields separated side by side. On the top are the output fields from divx and on the bottom are the source fields (which is how I want the fields to look).

Interlace error.JPG (http://youridol.bravehost.com/Interlace%20error2.JPG)

How can i make my fields look like the bottom two and not the top two?

[manono]

Hi-

You have to be careful how you crop and resize when you have an interlaced source. Try this:

LeakKernelBob(Order=1)#if TFF
Crop(xx,xx,xx,xx)
LanczosResize(xxx,yyy)
SeparateFields()
SelectEvery(4,0,3)#if TFF
Weave()

Be sure to load the LeakKernelDeint plugin first (or stick it in your AviSynth plugins folder). If that doesn't fix it, please post the script you are using. You may also be cropping incorrectly for your colorspace:

http://www.avisynth.org/Crop

[GodofaGap]

Are you using the latest version of DivX? I believe some older ones had some problems where the chroma of the first field got copied to the second field (which more or less seems to have happened here). I don't know if this bug got fixed though, but it certainly doesn't seem like a resizing issue/user error to me. (Since the fields aren't resized vertically on the pics posted.)

[Your_Idol]

Im using divx pro v6.2

the script i use looks like this:

separatefields
crop
resize
weave

I crop by a multiple of 2 and only resize verticly to a multiple of 16, leaving the horizontal resolution as a multiple of 16.

the fields look perfect in virtualdubmod before encoding but after, the colours are wrong.

Thanks

[GodofaGap]

Well, you resizing isn't safe (you should do it the way manono suggested), but it probably won't solve the issue at hand here.

[Your_Idol]

whats not safe about it?

resizing vertically before i separate will destroy the interlace. The fields will get all mixed together. What does manono's code do?

(i don't need LeakKernelBob and SelectEvery)

[manono]

Hi-

Seeing how you are resizing, I now agree with GodofaGap that it's not the problem. You can confirm or disprove his theory that interlaced encoding in DivX may be somehow messed up, by encoding for interlaced XviD and checking afterwards for similar artifacts.

resizing vertically before i separate will destroy the interlace. The fields will get all mixed together. What does manono's code do?

He's not suggesting that you resize the original 720x480 interlaced video, but the bobbed fields (LeakKernelBob), rather than the unbobbed fields as you're doing it. And he's right. The results will be slightly better.

[Your_Idol]

ok thanks
I'll get back to you about the xvid tomorrow

[Your_Idol]

yes xvid works just fine

I'll use it instead

but i prefer divx if someone can give a solution

[DigitAl56K]

Try this:

http://labs.divx.com/node/248

Encoding and playback should work within VirtualDub (i.e. with the VFW codec). We'll be fixing the DirectShow decoder shortly.