Interlaced or not

[edong]

My brother wants me to post some video clips recorded in his Sony miniDVD camcorder. These are SD with 16x9 aspect ratio. I will be using a free software to convert those to MP4 files before posting to YouTube. There is an option to interlace or not. Also I was asked odd or even field. I do not know the advantages of either choice. Thanks.

[aedipuss]

for computer video the cam's recordings will have to be de-interlaced and encoded to progressive. that's what youtube wants and hosts.

[edong]

That was quick! Odd or even field? Thanks

[aedipuss]

de-interlace means to remove interlacing. no fields - it becomes progressive.

[jagabo]

In other words, after deinterlacing even/odd field first no longer applies.

[edong]

Silly me. I got it backwards. Still, when interlacing, what is the advantage of choosing the odd or even field or there is specific requirement from the start (e.g., type of file) that I have to choose one over the other? Thanks for the patience.

[manono]

When interlacing? That makes no sense. What's the advantage of one over the other? That makes no sense either. They are what they are. If you have interlaced material and are keeping it interlaced, you have to know what the field order is so you can encode correctly. Otherwise you'll get stuttering playback. But one's not better than the other. You don't necessarily choose one over the other.

And none of this applies to deinterlacing video for upload to YouTube. You deinterlace it and you're done.

[jagabo]

Interlaced analog video is transmitted as a sequence of half-pictures, called fields. One half picture comprises all the even numbered scanlines (an even field), one all the odd numbered scanlines (the odd field). They are intended to be viewed one field at a time, one after the other, in the sequence they are transmitted. The transmission consists of a continuous, alternating sequence of even and odd fields, one every 1/60th of a second, each from a different point in time (ie 1/60th second intervals).

When a digital capture device captures interlaced video it weaves pairs of fields together into frames. It can start with an even field, then weave in the odd field to complete the stored frame, or vice versa. This is the field order, even field first in the former case, odd field first in the latter. In order for a playback device (eg. DVD player) to play the fields in the correct order it must know in which field order the capture device captured them, even field first, or odd field first. If it outputs the fields with the wrong field order you will get a two-steps-forward-one-step back jerkiness whenever there is motion.

Here's a guide someone posted a while back: http://www.movieconverter-studio.com/ivideo_en.htm

When you deinterlace a video you are turning the two half-pictures of each frame into a single whole-picture. Instead of two half-pictures at 1/60 second intervals you have one full picture at 1/30th second intervals. Since analog TV only supports interlaced video the single picture still has to be sent to the TV as a sequence of fields at 1/60th second intervals. But since a single picture represents a single point in time it doesn't matter if the playback device sends the fields to the TV in the wrong order. It doesn't matter which of the two fields you see first. Ie, the deinterlaced video no longer has a field order. Overall motion will be less smooth because you only have 30 motion intervals every second as opposed to the original 60.

Different programs use different terminology for field order. Even/odd, top/bottom, a/b, etc.

[edong]

Thank you guys for the explanation. Jagabo, that's a good one. Manono, how can I know the field order? Thanks.

This is why I posted the OP. Under "Deinterlace" I was given choices that made me curious. Just to let you know, I already was done with YouTube posting. I'm very satisfied with the output except that I thought I could have done better if I selected one of these. This is Daniusoft Video converter(free)

[manono]

Interlaced DVD is often but not always TFF, DV is BFF. To find out what you have you separate the fields using an AviSynth script such as this one:

AssumeTFF()
SeparateFields()

and then play the script or open it in VDub(Mod) and step through it. If movement is smooth, it's TFF. If movement is stuttering (like 2 steps forward, one step back) it's BFF.

Most of the deinterlace options given in programs such as the one you're using usually aren't very good.

[2Bdecided]

He's not asking about field order - just which one of those options to choose! You don't even need to know the field order for any of those options.


The software is just asking you which field to keep, and which to throw away. It doesn't matter at all.

It's also asking you what to do with the resulting gap - again, for YouTube, it doesn't really matter, but none of these options are good because this software isn't going a very sophisticated job of deinterlacing.


For SD DV > YouTube, I'd deinterlace properly. YouTube isn't great quality, but the results of crappy deinterlacing (i.e. just throwing away one field) are still visibly poorer on YouTube than doing a better job. However, top-notch deinterlacing takes time, so unless you want to spend more time on it, just stick to throwing one field away.

I often upscale for YouTube - not because SD upscaled to HD looks better in itself (it can, if you do it really well, but not much), but because YouTube makes HD sources available at a higher resolution and bitrate, which looks better on Youtube even if the original was SD.

Cheers,
David.