Worth converting "old" divx to "new" divx? (Plus more

[DK-II]

Will there be any improvement if I re-encode a divx file with a newer version of divx? What if the original file has no bvops but the new one does?
What about re-encoding an xvid file which has no qpel or bvops so that it does have qpel & bvops? Will the bitrate of the new file automatically be lower than the original because of xvid's smart encoding (only using bits when necessary)?
Converting from divx to xvid is supposed to be lossy but what if you convert from 0 bvops to 3 consecutive bvops & from no qpel to qpel? Will the gains outweigh the losses?
Thanks in advance, I looked but couldn't find answers to these questions so hope I'm not asking questions that have already been answered before. I know some of this is subjective so hope to hear as many opinions as possible.

[loster]

not really unless you are trying to get the file to work with or on certain hardware because quality is lost with reencoding. If you want this AVI ReComp is capable of doing this for divx dvd players.

[TBoneit]

IMHO not worth converting as you will lose quality. Even with the changes you mention they require re-encoding and a quality loss.

If you are trying to make them smaller? Then start over using the originals. If disc space is an issue burn them to two sets of backup media, CDs or DVDs and erase them from the computer. Sooner or later you will regret the lost quality.

I'm happy to get all the quality I can and if that means one 2 hour video on a DVD, then at $0.28 a disc I can afford it. 28cents is a cheap enough cost to make my eyes happy. Now that I've gone to a HDTV I'm glad I kept things as good as possible. I regret the VCDs I used to make as they now look poor. In that case as I erased the captures and the source I'm stuck. On the S-VHS family tapes I did keep the originals that were recorded at the 2 hour speed so I'm redoing them. If I'd have kept the quality high to start I'd have saved myself the time I'm using up now.

Cheers

[DK-II]

Thanks guys! I just wanted to see if I could make the files smaller without losing quality. I don't have a DVD burner so I burn to VCD. It's just nice to pack as much onto 1 disc as I can. Just to be clear, converting from no bvops to 3 consecutive bvops (xvid to xvid) won't be worth it despite the efficiency of bvops?

[celtic_druid]

DivX 3 (aka MS MPEG-4 V3) didn't have B-VOP's. Wasn't actually even technically MPEG-4.

If you were to re-rip using a current XviD/DivX build with bframes, then yes you could easily beat an old SBC encode.

Few points though. Re-encoding with a lossy codec always causes quality loss. Whether or not you can see it or not is a different matter, but to achieve a significant size drop chances are that you would.

Re-encoding is a waste of time anyway if you are only then going to convert to VCD. VCD is always 10MB/min.

The number of max consecutive bframes is just a number. Still up to the encoder how many to insert (upto the max of course).

[Ai Haibara]

Re-encoding is a waste of time anyway if you are only then going to convert to VCD. VCD is always 10MB/min.

Plus, if you re-encode once to 'upgrade' the video to the newer DivX format, then convert it to VCD, that's going to be two different hits against the quality of the video, as well.

[TBoneit]

If you mean a real VCD then there is no .avi on the disc. If you had a 10 megabyte avi that ran for 70 minutes and converted it to VCD it would fill the disc. The 10Meg file wouldn't really be watchable of course but in a true VCD it is playing time and not the size of the source.

The other option would be if you are using the term VCD incorrectly and are calling any CD with video on it a VCD.

If you are always starting out with avi why not just get a DVD player that can also play Divx/Xvid?

[DK-II]

Sorry, I'm too used to saying VCD when I actually mean a data CD with divx or xvid files on it. My DVD player can play divx & xvid & it can also handle files with 3 consecutive bvops. I just wanted to convert to more bvops to make the file smaller without losing picture quality if possible. Looks like it won't be worth the hassle. I should really learn that re-encoding is always likely to cause loss of quality & should only be done if it's necessary to play the file. I always convert wmv to xvid because my DVD player can't play wmv.

Thanks again!

[TBoneit]

That is sort of what I thought you might be meaning.

Keep in mind that discs are cheap and a dvd disc is not much more than a cd disc to buy but holds so much more. Maybe it is time to get a DVD burner? This of course would depend on whether or not your player will play Divx on a DVD.

I don't even bother to convert WMV to another format. I just play them on the computer and watch them on the TV. Not quite as convenient as using a remote for FF and such but much quicker and the quality takes no hits at all that way. OTOH Divx/Xvid I do burn to a DVD so I can watch them on either floor and have the use of the remote.

[DK-II]

I often resize the picture so that none of it will be cut off when played with my DVD player on my TV. Should I just re-encode the file with the same codec & settings as the original (except for the image size of course) or is there anything else I should do to reduce loss of quality when resizing (I normally use bicubic resizing or whatever's supposed to give best quality)?

[FulciLives]

Re-encoding an XivD or DivX to another XviD or DivX is a process that will result in loss of quality. There is no way around that fact.

As someone else already suggested the only time I would do that is if:

1.) The XviD/DivX does not work on your stand alone MPEG-4 capable DVD player
2.) You don't have the "source" and just have the DivX/XviD file

Otherwise forgot about re-encoding as it will lead to loss of quality. Period.

- John "FulciLives" Coleman

[DK-II]

Yes, but to fit the whole image onto the screen I have to re-encode so what's the best way to do this (I know it will be lossy, but I still want to resize the image)?

[FulciLives]

Yes, but to fit the whole image onto the screen I have to re-encode so what's the best way to do this (I know it will be lossy, but I still want to resize the image)?

Are you saying that you have subtitles that are getting cut off? I mean all televisions (well pretty much all except maybe for some LCD and Plasma screens) have TV OVERSCAN which is a term used to describe the fact that the image edges (top, bottom, left, right) are "masked" by the TV ... this does not exist on a computer monitor.

So sometimes people think they aren't getting "all" of the picture and yeah you aren't on a TV but that is normal and movies know this ... especially anything made specifically for TV but even film will keep really important stuff from the very extreme right/left edges.

However a lot of the "fan boys" that do "fan subs" on videos (usually Japanese anime) have this horrible habit of putting the subtitles down so low on the image that while it works on a computer monitor it doesn't work on a TV because the TV OVERSCAN hides some of the subtitles.

So that would be the only time I would re-encode.

How to do it?

Read this here thread ---> CLICK HERE

Now that thread talks about converting a MPEG-4 to DVD while accounting for TV OVERSCAN but you can easily adapt it to MPEG-4 to MPEG-4 by picking your output as being 1:1 in FitCD which is the program that helps you figure it all out.

- John "FulciLives" Coleman

[DK-II]

No, it's not because of subtitles, I just like to see the whole image especially when my TV cuts off a lot of it. I know that overscan is normal but I still want to see the whole image. All I want to know is if I am going to re-encode does using a different codec reduce quality even more than using the same codec as the original e.g if the original was encoded with divx would re-encoding with xvid result in a worse image than re-encoding with divx. Is re-encoding lossy because any codec is lossy or is it lossy because you're using a different codec than used for the original encoding?

[FulciLives]

No, it's not because of subtitles, I just like to see the whole image especially when my TV cuts off a lot of it. I know that overscan is normal but I still want to see the whole image. All I want to know is if I am going to re-encode does using a different codec reduce quality even more than using the same codec as the original e.g if the original was encoded with divx would re-encoding with xvid result in a worse image than re-encoding with divx. Is re-encoding lossy because any codec is lossy or is it lossy because you're using a different codec than used for the original encoding?

It is lossy because you are re-encoding meaning yet another compression so no matter what codec you use (DivX or XviD or MPEG-2 or H.264, etc.) quality will be lost. It makes no difference if you go from XviD to XviD or XviD to DivX or whatever. However MPEG-4 (be it XviD or DivX) is already a very heavily compressed format so when you try to re-encode it to another very heavily compressed format (i.e., MPEG-4) then the loss is even more evident.

As for the TV OVERSCAN ... you are being childish. Also generally speaking only some older televisions or some new yet dirt cheap crap ass televisions overscan "excessively" so maybe you just need a new TV ... and a chill pill to boot.

- John "FulciLives" Coleman

[manono]

Every TV show, VCR tape and DVD you've ever watched has lost video to the overscan. If it didn't bother you then, why should it bother you now?

It's lossy because MPEG-4 codecs such as DivX and XviD are lossy. It doesn't matter if you keep it the same codec, or change codecs. Uncompressed codecs are lossless, but give huge file sizes. You lose quality just from reencoding. You lose quality because it sounds like you're a neophyte and may not know the optimum settings. You lose quality because you're shrinking the active video resolution (if adding black around the outside but keeping the same resolution) and losing even more detail and sharpness. Depending on the quality and size of your TV, none of this loss may be noticeable to you. Sounds like you don't much care anyway.

[DK-II]

"As for the TV OVERSCAN ... you are being childish."

Less of the name calling & sarcasm please! What's it to you if I want to see the whole image? If I want to sacrifice quality in order to see the whole image that's my problem, not yours, so don't call me childish.

[FulciLives]

"As for the TV OVERSCAN ... you are being childish."

Less of the name calling & sarcasm please! What's it to you if I want to see the whole image? If I want to sacrifice quality in order to see the whole image that's my problem, not yours, so don't call me childish.

I already called you childish.

Now I'm calling you a clueless jerk.

Shall we continue?

- John "FulciLives" Coleman

[DK-II]

Manono, it bothers me because sometimes there's a logo or some kind of text that gets chopped off & it draws attention to the overscan.

I'm not a neophyte as such. I have some idea of what settings to use but I didn't know that re-encoding will always be lossy when using codecs even if you use the same one again. I'm gradually learning more & more about encoding with different codecs. I used to convert from xvid with no bvops to xvid with 3 consecutive bvops coz I thought that would reduce file size with no loss of picture quality but I have recently discovered (from earlier posts in this thread) that it's probably not worth it. I know the bicubic method is recommended for reducing image size so I normally use that & I haven't really noticed any reduction of image quality. Since getting a divx / xvid compatible DVD player I tend to convert all my wmv, divx & xvid files to xvid with 3 consec bvop, qpel, lumimasking, keyframe every 10s (minimum) & packed bitstream. I also reduce the resolution dimensions by 90% each (e.g 480x360 to 432x324) but add a black border so the resolution actually ends up staying the same. This results in the image almost perfectly fitting my TV screen. Any advice on what I'm doing wrong would be appreciated (bear in mind I would prefer to continue to resizing even if it is childish).

[DK-II]

"I already called you childish. "

How observant of you, Sherlock!

"Now I'm calling you a clueless jerk."

There's a reason why people use these forums, to learn new things. We all have to start somewhere so stop being an arrogant ass!

"Shall we continue?"

I think I've already answered this stupid question for you.

[celtic_druid]

Shouldn't that be "arse"? Your location does say UK.

Ok we already covered lossy re-encoding. Fact is that if your TV overscans and your player can't zoom out or expand the video, then you don't have any choice if something is being noticeably cut off. So just do it and see if the quality loss is acceptable to you. If you don't resize (might not be possible depending on the resolution (most SAP's support 720x576 max)) and use a suitably high bitrate, then the quality loss shouldn't be that noticeable.

[manono]

From what you said about your settings, I guess you do know more than I figured, based on some of the other things you've said.

Luma masking? Are you using a real old XviD, by chance? I thought it was called Adaptive Quantisation now. In any event, I don't much like it, as it messes up dark areas, and makes them blocky. That is, it accentuates the so-called "black" or "dark blocks" for which MPEG-4 is notorious. My standalone doesn't handle Q-PEL, so I've never used it. My standalone also prefers packed bitstream, and I've always used 1 B-Frame, although 2 is pretty much the standard. I've never used 3.

If I'm understanding celtic_druid correctly, he made a good suggestion. Instead of resizing your 480x360 AVI down to 432x324 and adding black to bring it back up to 480x360, you might try keeping it at 480x360 and adding black to make it 528x396 (although I might prefer 528x400 to maintain Mod16 dimensions). That way no resizing is necessary. If using AviSynth:

AVISource(C:\Path\To\Movie.avi")#adjust for your path and name
AddBorders(24, 20,24,20)

and send to VDubMod and encode using Fast Recompress, rather than Full Processing.

[celtic_druid]

Yep, that is exactly what I meant. Add say 16 pxiels to each side or you could start with 8. Just depends on how much the TV overscans and the resolution of the file (low the resolution, the higher percentage 16 pixels would be).

If the file was say 704 pixels wide though and you added 24 to each side as above then that would mean too many pixels for most SAP's (any HD capable one should be able to zoom out in small enough increments to sort out overscan).

[DK-II]

"Shouldn't that be "arse"? Your location does say UK."

Not necessarily coz I might mean "ass" as in the animal Even if I did mean "arse" I might as well talk to the guy in his own lingo to make sure he understands me.

"Luma masking? Are you using a real old XviD, by chance? I thought it was called Adaptive Quantisation now. In any event, I don't much like it, as it messes up dark areas, and makes them blocky."

It is called adaptive quantisation now but I still call it lumimasking. It does make dark areas blocky but it doesn't bother me because it isn't that noticeable & the saved bits can be used elsewhere where they'll hopefully be more useful (I think).

As for adding a black border without shrinking the image first I had considered that before but was never sure which method to use (keeping image size but then adding border to increase size overall or reducing size & then adding border to keep same size overall). Instead of using Avisynth can I not just add the border with VDubMod or would that require Full recompressing?

Thanks for your help guys

[manono]

Hi-

Instead of using Avisynth can I not just add the border with VDubMod or would that require Full recompressing?

So you're one of those guys that just drops his AVIs into VDubMod? My respect for you just dropped back down a couple of notches. Yes, you can do that in the VDub resize filter, by checking the "Expand Frame And Letterbox Image" box, and then giving it the new resolution. As is the case with any VDub filtering, you'll have to use Full Processing.

But just how hard would that script above be to adapt for your movie and open in VDubMod? c_d suggests something like this (and, as usual, he's right):

AVISource(C:\Path\To\Movie.avi")
AddBorders(16,16,16,16)

You can tune the AddBorders numbers based on how much your TV set overscans.