aren't most avi's non-interlaced

[catdaddio6]

since i started doin alittle capturing with huffy,,i've had to wonder,aren't most divx and xvid non-interlaced,,,since they are clear on monitors??and wouldn't encoding them to interlaced go against the if its progressive leave it progressive idea??

[adam]

Yes. Interlacing is an archaic workaround which is only necessary for tv playback. If its going to be played on a pc monitor, which is progressive, then its best to store it progressively. Most DVDs are progressive and so keeping it this way for an xvid or divx conversion is simple. For those that are interlaced, its better to deinterlace. It could be done by the playback software, but doing it yourself would be higher quality and require less CPU power to play it back. Also, for a while divx didn't even support interlacing.

As long as the codec supports it, interlacing is possible. Divx and xvid are just typically used for pc playback, so there's no point keeping/making it interlaced.

[catdaddio6]

i read somewhere that if its progressive leave it progressive and if interlaced leave interlaced,,,if most dvds are progressive shouldn't they not look as good as they do on television,,and if i am goin to encode a xvid to dvd,then shouldn't i leave that progressive also,,instead of onterlacing them as i have been doin???thanks for reply by the way

[Anonymous321]

The thing is, that interlaced material plays at 50 fps (PAL, it's 60 fps NTSC). That makes it 50 half frames per second, but they are 50 DIFFERENT frames, NOT 25 frames each split to two frames. So if you have a camcorder movie or something recorded from tv, you usually deinterlace that video using blend mode, which blends every two frames together, making it 25 fps progressive.

A DVD usually plays 25 or 24 fps progressive. interlacing them wouldn't cause any affect, since you would have 50 frames where every two frames are actually the same.

I do a lot of filming, and when I convert to xvid, I do a version with 25fps in blend mode, and a 50fps version for download. And also because my laptop isn't fast enough for the 50fps version.

This is the site which explains the whole interlaced thing very good:
http://www.100fps.com/

[chicola]

Shao-Domi,

Use frames and fields in your explanation!

[Anonymous321]

I explain it the easy way since this is the newbie forum. Whoever wants it more specified should check out the website I gave the link to.

[adam]

DVDs use progressive frames (typically) and are telecined at playback. For PAL each frame is split into two fields. For NTSC, you first split each frame into two fields and then you repeat fields in a set pattern, ususally 2:3 to increase the framerate to 29.97fps. But the point is that the video is physically stored on the disk at 23.976fps using progressive frames (frame pictures).

If you have a progressive xvid source then you should do the same. Encode it as progressive 25fps, or progressive 23.976fps and include pulldown flags which instruct the DVD player to telecine the movie to 29.97fps.

Either way, if its played on non-progressive tv, its going to be interlaced by the DVD player. But if you encode it progressively, you get numerous quality benefits.

But as already mentioned, if the source is actually interlaced in such a manner that the interlacing process cannot be reversed, then its best to leave it that way because the effects of blending the fields is usually much worse then the benefits gained when using progressive encoding.

[SaSi]

DVDs use progressive frames (typically) and are telecined at playback. For PAL each frame is split into two fields. For NTSC, you first split each frame into two fields and then you repeat fields in a set pattern, ususally 2:3 to increase the framerate to 29.97fps. But the point is that the video is physically stored on the disk at 23.976fps using progressive frames (frame pictures).

It's an old argument discussed plenty, I believe, but:

I checked the video stream I ripped out of a typical DVD. It's marked as interlaced (field encoding).

I understand that this is the syntax of the video stream.

If the DVD contains a movie, since the source (film) is by design progressive, the interlace flag in the video stream merely indicates that the video was encoded in interlace mode. (i.e. the frame is split into to fields).

Such a movie can be encoded to progressive (where the two fields are merged together) to produce a perfect picture. The picture is perfect and no artifacts occur as each frame of the original film is scanned to create a frame. If you put the movie in a timeline, both fields correspond to the same moment in time.

On the other hand, TV broadcast of live events or a TV series "filmed" with a video camera or captures of analog camcorder tapes, are interlaced both syntactically and in actual content.

In this case, if you put the movie in a timeline, every field has a difference of 1/50th of a sec (for PAL) from the next. This means that merging the two fields cannot produce a perfect picture since 1/50th of a second has passed between the capture of each field.

Such a movie can also be encoded to AVI and some codecs preserve the interlace nature of the content. Such movies typically show "comb-lines" when played on a computer but play well on an interlaced TV.

[adam]

Sasi, that is most likely the sequence flag you are looking at and yes, it is always required to be set to interlaced for DVD. But the prog_frames flag can be set to either frame or field depending on whether you encode progressively (use frame pictures) or as interlaced (use field pictures.)

Almost all DVDs are encoded using frame pictures. There are physically two fields present, but they are displayed at the same time, in other words, as a frame. Of course when played back these fields are split and telecined, but the point is that you are in fact encoding progressively, and storing it as such on the disk.

The old, is a DVD progressive or interlaced argument. The answer is that it is usually both, but you can just treat it as progressive in all respects as long as you remember to set your flags correctly in the end (prog_seq=interlaced, prog_frames=progressive, and RFF/TFF set if encoding NTSC.)

[SaSi]

Sasi, that is most likely the sequence flag you are looking at and yes, it is always required to be set to interlaced for DVD. But the prog_frames flag can be set to either frame or field depending on whether you encode progressively (use frame pictures) or as interlaced (use field pictures.)

Almost all DVDs are encoded using frame pictures. There are physically two fields present, but they are displayed at the same time, in other words, as a frame. Of course when played back these fields are split and telecined, but the point is that you are in fact encoding progressively, and storing it as such on the disk.

The old, is a DVD progressive or interlaced argument. The answer is that it is usually both, but you can just treat it as progressive in all respects as long as you remember to set your flags correctly in the end (prog_seq=interlaced, prog_frames=progressive, and RFF/TFF set if encoding NTSC.)

Agreed,

To put my statement in other - fewer - words,

encoding a movie that originates from a film with the "wrong" field order results in a perfectly viewable DVD.
encoding a TV capture with the wrong field order, results in the fastest way to get sick

[adam]

Ok. I thought we were both saying the same thing, but I wasn't sure.

[LisaB]

Hi,

Does anyone know how to tell if the video in an avi has been encoded using a field-based encoding? I'm not even sure if there even *is* such a thing as field-based divx encoding, but that seems to be what the originator of this thread is implying....

Would G-Spot somehow indicate this?

[adam]

Actually, "field based" and "frame based" encoding are something entirely different. The DVD standard itself doesn't even support "field based" encoding. But that's just me being picky, I know what you mean.

You are talking about using field pictures instead of frame pictures, and yes divx does support this. If I wanted to confirm that my avi was interlaced (field pictures) I would just look at it. Open it any video editor and see if the interlacing is visible.

[catdaddio6]

i wondered bacuse alot of xivds are divx guides say to use bottom field to encode to dvd or svcd,,but the motion is never smooth,not jerky,just not smooth,,,,then i started capturing some olg fights of mine to pc using the huffy and iuvcr,,thats when i first noticed the interlacing lines and became curious about it since you dont usually see them off any xvid or divx,,so i guess those should be encoded with progressive from now on,,,now about dvd's being 23 frames,,im in ntsc land,,then why when you encode its usually in 29 frames and says to use bottom field generally if they are progressive by nature???

[LisaB]

Adam, maybe you meant to say the dvd standard doesn't support "frame-based" encoding?

If you look at TMPGEnc encoder, for instance, you can choose interlace or non-interlace "Encode Mode". Most every DVD I've seen, irregardless of whether the source was progressive or interlaced, uses interlace encode mode...in other words, encoded as a series of fields and not as a series of frames....if it weren't for this, then the RFF tags, etc., wouldn't work as intended...

In my understanding, the encode mode has nothing to do with whether the source is interlaced or not....both interlaced and progressive material can be encoded either as frames or fields, though I think it's smarter to encode interlaced source as fields, for efficiency purpose.

Whether or not you see interlacing effects in the frames will tell you whether or not the original source material was video or film, but as far as I know, it will not tell you anything about whether the encoded video is stored as fields or frames....

I always thought that all divx was encoded as frames. However, I notice in the XviD Profile options is something called "Interlaced Encoding". Now, I have no idea if this just refers to an "algorithm" for efficient frame-based encoding of interlaced material...or whether choosing this option would actually result in a truly field-based encoding where the fields are encoded as distinct entities...

I've asked this question a long time ago, and never got an answer, so anyone who has more info or correction, please jump in.

[adam]

Adam, maybe you meant to say the dvd standard doesn't support "frame-based" encoding?

If you look at TMPGEnc encoder, for instance, you can choose interlace or non-interlace "Encode Mode".

No, I meant fields. The DVD standard does not support field based encoding, and the only encoder I know of that can even do this kind of encoding is Procoder.

When you select interlaced or non-interlaced (progressive) in TMPGenc or just about any other encoder, you are selecting whether you use frame pictures or field pictures. This is entirely different then "field based encoding" or "frame based encoding."

Even when you select interlaced source and output in TMPGenc, you are still doing frame based encoding. Check out Procoder's documentation to find out what true "field based encoding" is, but the output wont play back on most dvd players from my experience.

Most every DVD I've seen, irregardless of whether the source was progressive or interlaced, uses interlace encode mode...in other words, encoded as a series of fields and not as a series of frames....if it weren't for this, then the RFF tags, etc., wouldn't work as intended...

No. Most every DVD uses frame pictures, or in other words would have had non-interlaced output specified in the encoder. This specifies that each pair of fields will be displayed at the same moment in time, and that the prog_frames flag will be set to progressive.

It is the prog_sequence flag that must always be set to interlaced in order for RFF/TFF routines to work properly. Again, even when you encode using frame pictures each odd and even field is still a separate entity, its just played back at the same time.

Check out DVD Demystified FAQ for more info on frame pictures versus field pictures.

[catdaddio6]

so why do i see field or frame lines in a captured avi,but not in a xivd,divx,or dvd file that is still in vob files,,if the dvd were interlaced,wouldn't the fields show up like a capture does on monitor,,should i even encode these things with iterlacing or should they be left progressive

[adam]

As already stated, most divx and xvid you come across will be progressive since they are generally intended to be played on a pc.

As for DVDs, most software players perform a bob and weave process on the DVD just like a progressive scan DVD player does. It still performs a RFF/TFF conversion, but it uses the new fields differently. Basically you just get progressive playback. If you played the vobs themselves through a software player that doesn't deinterlace interlaced sources (most do) then yes you would see the interlacing. You could also easily see the interlacing lines by loading the video into an mpeg editor or encoder and viewing them frame by frame.

Like I said, DVDs are only interlaced in the sense that each frame is made up of two fields, so that they can be split again when played on a tv. When viewed as is, it still just looks like a progressive frame, because that's what it is.

Try this. Run an NTSC vob through dvd2avi. Try it once with forced film turn on. This bypasses the RFF/TFF flags and gives you the footage as its stored on the disk. Load the d2v file it creates into TMPGEnc and use its preview function. Go through frame by frame and you will see whole progressive frames.

Now run dvd2avi again with forced film turn on. This processes the RFF/TFF flag and gives you output as it would be sent to the tv. Now load the d2v file into TMPGEnc and again look at the preview frame by frame. You will see 3 progressive frames and then two "interlaced looking" frames. Those additional fields were literally created by the decoder. They don't exist on the original DVD.

The fact that a DVD is technically an interlaced stream is only noticable when you physically separate those fields and perform the telecine at playback. Since it is still stored using frame pictures, it appears in all other respects to be entirely progressive.

[GreatScott]

ABOUT Interlaced Encoding
http://www.vrac.iastate.edu/~chadspen/interlace/index.html