progressive and interlaced mixed

[k-c-ksum]

about to back up Dr Who reg2 (latest season)
DVD-RB sets avs up with this :

ConvertToYUY2(interlaced=true)

when skimming through mpegs its seams its only the end credits that are interlaced while the rest looks progressive.

if i replace :
ConvertToYUY2(interlaced=true)
with ConvertToYUY2 and fielddeinterlace() will the progressive segmnets remain the same or would i have to only set deinterlace to the interlaced segments?

[jdobbs]

You really can't just "look" and determine whether it's interlaced. DVD Rebuilder reads the flags embedded in the MPEG stream to make the determination. I would trust what it says.

[Boulder]

Probably ~95% of PAL releases are flagged as interlaced even though they are progressive. This is done just to be safe, I guess the releasers just encode and author stuff as fast as they can. Encoding progressive material as interlaced doesn't do any harm (apart from the fact that it'll require more bitrate than encoding as progressive) but encoding interlaced as progressive does Very Bad Things.

I always inspect the video before doing anything and then disable interlacing if needed. This is due to the difference in bitrate requirements as we're dealing with less available space and all the bits should be well spent.

[Sir Didymus]

Hi Boulder!

Agreed most of the PAL releases are un-necessarily flagged as interlaced, and I perform the same careful visual inspection, before encoding, in order to disable interlace, if possible.


Encoding progressive material as interlaced doesn't do any harm (apart from the fact that it'll require more bitrate than encoding as progressive)...


That part is interesting: I always supposed the higher bitrate requirements for encoding the same stream as interlaced instead than progressive exist but are marginal respect to other factors: after all the spatial content (bits in the uncompressed frames versus bits in the uncompressed fields) is the same, and the temporal content (motion vectors) should be more or less equivalent...

So I supposed the higher requirements were due basically to the overhead of encoding twice, a smaller content (the fields), instead as just once, the whole frames...

Anyway, never performed any tests on my own...

Do you have some references on the matter ?

Cheers,
SD

[Boulder]

That part is interesting: I always supposed the higher bitrate requirements for encoding the same stream as interlaced instead than progressive exist but are marginal respect to other factors: after all the spatial content (bits in the uncompressed frames versus bits in the uncompressed fields) is the same, and the temporal content (motion vectors) should be more or less equivalent...

So I supposed the higher requirements were due basically to the overhead of encoding twice, a smaller content (the fields), instead as just once, the whole frames...

Anyway, never performed any tests on my own...

Do you have some references on the matter ?

Cheers,
SD
Unfortunately I cannot find a "simple" explanation, or a scientific paper in which this would be explained. One factor is that alternate scanning order is more suitable to interlaced sources and should be less efficient when compressing progressive material compared to zigzag scanning.

Could it also be that the compression efficiency is better when you have a full size frame to make use of? I'm not sure..

I'll run some tests later today when I get home, I've not done any accurate test on the subject either.

There are some people who probably know this stuff well so I hope they'll happen to bump into this thread.

[stereo]

@Boulder

I always inspect the video before doing anything and then disable interlacing if needed.

Previously, i've neglected to encode interlaced PAL as progressive. Mostly, because I was unsure how to decide if the source was incorrectly flagged as interlaced (and was, in fact, progressive). So maybe you can help me: How do I determine if the flagging is correct or incorrect?

Thanks!
/stereo

[Sir Didymus]

Simply drag the source vob into DgIndex or a similar application allowing to view the individual video frames. The interlaced contents is immediately visible, especially in the moving scenes.

But please, pay a lot of attention! In some (not at all rare) case, the video stream have a mixed content, as in the example of k-c-ksum. If you just walk quickly on the stream you may easily miss the interlaced content, wrongly assuming the stream is progressive in all of its extension.

Even in case of a minimal doubt, leave the choice to DVD-RB:
wrongly encoding a progressive stream as interlaced is just a little bit not efficient, but wrongly encoding an interlaced stream as progressive lead to disasters (and it's also a big self-inflicted mistake, in case it was properly flagged, in origin, as interlaced)...

[stereo]

OK, thanks, Sir Didymus! I'll give it a go, but I guess it really isn't worth the hassle - at least not if the gain is as insignificant as you (and others) suggest.

At any rate, I appreciate your answer!

/stereo

[k-c-ksum]

i can clearly see interlaced material when previewed in Media player Classic.

So if i set Fielddeinterlace() and ConvertToYUY2 will this effect the already progressive parts?. I use RBOpt for quick avs editing so all segments get set.

the only short cummings i see is any deinterlaced segments will look soft and not as fluid. If its only Credits that are interlaced then i can live with them being soft :)

[Boulder]

Why do you deinterlace at all?

[k-c-ksum]

Why do you deinterlace at all?

if its only the credits that are interlaced then if i deinterlace and encode as progressive along with the already progressive segments it opens up the option of using filters that only work on progressive streams

[Jeffster]

i can clearly see interlaced material when previewed in Media player Classic.

You CANNOT reliably determine if your source is interlaced by viewing it in Media Player Classic or any or media player. Most, if not all, have built-in deinterlacers which will disguise what you are seeing.

Do as Sir Didymus suggests and view in DGIndex or better yet load the AVS in VirtualDub and step through frame by frame very carefully!

Most of the PAL DVD's I've seen are flagged as Interlaced but 99% of them are actually Progressive. The Extras on the disc are an exception and often Interlaced, also TV series which is what you have... so don't assume anything from viewing at normal speed in a media player.

[k-c-ksum]

all im asking though is will a progressive segment get screwed up if i set it as fielddeiterlace()

[Boulder]

Better option is to disable Decomb and use the filter editor and set FieldDeinterlace(full=false). That way only the parts detected as combed will be affected. AFAIK the default settings for FieldDeinterlace work very well in such cases.

[jdobbs]

This is a really tricky issue. Here's MHO:

The bottom line is that if a progressive source is marked as interlaced it plays back fine. But if the source is interlaced and is force to be treated as progressive -- is looks terrible. You can't trust what you think you see -- players do lots of funny things. You should only change the format of the original from interlaced to progressive if you absolutely, positively, unquestionably know that the source is undoubtably, conclusively, and undeniably progressive -- and even then you should still have reservations.

[uroscar]

I'm gonna backup my DVD. I would just like to know should I check Deinterlace with Decomb, or should I leave it blank? Source is a Friends DVD NTSC.

Thanks!!!!

[Boulder]

Friends should be progressive. Leave the setting blank, in any case you should never deinterlace if you watch the DVD on your TV.

[jdobbs]

Definitely leave it unchecked.

[uroscar]

Yes, you are right. I will watch it mainly on my TV. What about if I do a NTSC movie?

[Boulder]

Like I said, never deinterlace. Besides, probably 99% of all movies are progressive.

[uroscar]

Thank you for the fast reply. You are really friendly. And thanks for the great program Jdobbs!!!!

[jdobbs]

Deinterlacing is available to support some very special circumstances. It should be rarely used.

[zilexa]

Ok this topic is about interlaced dvds, some flagged as interlaced but are in fact progressive.

Just to be sure:

I rebuild the dvd Enemy of the States, it's a progressive DVD.
But DVD-Rebuilder .97 (using HC .17 encoder) encodes the dvd as interlaced!
If I understand correctly, this has the disadvantage it uses more space..

But I don't have a clue how to set dvd-rb not to encode interlaced, and why it does it like this.

[Boulder]

It's the "Disable interlaced" option. DVD-RB encodes as interlaced if the original is flagged as interlaced.

[jdobbs]

An interlaced disc takes no more space to encode than a progressive one. Also, you can't make an interlaced disc progressive. If DVD-RB says the disc is interlaced -- then the stream is interlaced according to the MPEG flags within the stream itself.

The "Disable Interlaced" option was added to be used only on PAL sources that the flags set for interlaced when the source is progressive. If your disc is NTSC, and DVD-RB tells you it is interlaced... the odds are 1000:1 that it is interlaced and you should leave it alone. Trying to encode an interlaced disc as progressive will make a mess almost every time.