Encoding a DVD to DivX and aspect ratio

[DVDHack]

I have read a ton of stuff on aspect ratios in this forum and several others but I have a failure in understanding which I'm hoping I can clarify.

If I take a DVD at 720x576, why can't I take it and encode it at 720x576 and have the TV display it at 16x9? Is it that the DivX encoder will not do the stretch in the horizontal to 1024? It seems to me that we suffer in quality by reducing the verticle resolution to around 400 lines to get 16x9. I know this isn't an issue at the moment when playing back on a TV but it may be a big issue when I eventually can afford a projector and it can support the 576 lines.

Sorry all the numbers are for PAL at 720x576

Thoughts?

[Sephiros]

Hi

You can encode it in 720*576, but you will encode black borders as well, which is a great loss. That is why you must crop the top and bottom and end up with more than 100 pixels cropped (for true anamorphic), and have the resolution of about 720*476.

I've never had the chance to playback my divx on 16:9 TVs, but my guess is it needs a full 720*576 image to then crops the black border itself.
Whatever is the format of the DVD: Anamorphic, Full Screen or Letterboxed, it MUST has the standard resolution of 720*576 on PAL regions and 720*480 on NTSC (our TVs sux... :P)

[DVDHack]

But the DVD doesn't have black borders they are added by the frameserver. If you encode just the DVD source it will not add any black ie a 1:1 encode. The standard 720x576 is all image. The DVD player adds the black borders when you display it on a 4:3 TV when you select 16:9 on a DVD player it adds nothing.

[TheWEF]

Originally posted by DVDHack
If I take a DVD at 720x576, why can't I take it and encode it at 720x576 and have the TV display it at 16x9?

because (if configured correctly) tv-out will stretch the picture according to ITU TV standards assuming that the pixel aspect ratio of your desktop is 1:1.
this has nothing to do with whether the dvd is anamorphic or not or whether you set your tv for anamorphic display or not.

wef.

[jggimi]

Originally posted by DVDHack
But the DVD doesn't have black borders they are added by the frameserver. If you encode just the DVD source it will not add any black ie a 1:1 encode. The standard 720x576 is all image. The DVD player adds the black borders when you display it on a 4:3 TV when you select 16:9 on a DVD player it adds nothing. I don't believe this is correct, and borders are in the DVD video stream.

720x480 (1.5:1) or 720x576 (1.25:1) are the fixed sizes of the DVD video stream, and the stream will include letterboxing to display at the stream's configured DAR (4:3 or 16:9). In that sense, all DVDs are anamorphic as there is resizing from the DVD stream to the DAR. Click here (http://www.widescreenmuseum.com/widescreen/squeeze.htm) for more on Anamorphism in film.

Example: CinemaScope content (2.35:1) transferred to NTSC DVD (1.5:1) with DAR of 16:9 (1.78:1) will have letterboxing to resize the picture portion's aspect ratio back to 2.35:1. If you display on a 4:3 TV, your player will add additional letterboxing.

[MrDarcy]

Originally posted by DVDHack
The DVD player adds the black borders when you display it on a 4:3 TV when you select 16:9 on a DVD player it adds nothing.

AFAIK, black borders are added by a 4:3 TV set when it detetcts anamorphic input signal.

[MrDarcy]

Originally posted by DVDHack

If I take a DVD at 720x576, why can't I take it and encode it at 720x576 and have the TV display it at 16x9? Is it that the DivX encoder will not do the stretch in the horizontal to 1024?
Thoughts?

My very short experience: a DVD contains 720-per-row anamorphic (not squared) pixels that, in a 16:9 TV-set, are enlarged to fit the whole screen.
The DivX encoder creates only 1:1 (squared) pixels, so the same 720-per-row pixels appear narrower and you need black borders to obtain the correct aspect. But these borders don't need to be encoded to save bytes.

But I'm a real newbie and I hope someone will correct what I wrote :)

Bye!

[Sephiros]

Originally posted by MrDarcy
My very short experience: a DVD contains 720-per-row anamorphic (not squared) pixels that, in a 16:9 TV-set, are enlarged to fit the whole screen.


It's absolutely true!, in NTSC, 16:9 pixel aspect ratio is 40:33 if I'm not mistaken, and 4:3 aspect ration is 10:11.

For PAL people, it's 118:81 and 59:80.
So easy and simple, heh?! lol :)

edit:

Just found this URL, it's very interesting if you want to know more:
http://www.mir.com/DMG/aspect.html

[TheWEF]

Originally posted by Sephiros
It's absolutely true!, in NTSC, 16:9 pixel aspect ratio is 40:33 if I'm not mistaken, and 4:3 aspect ration is 10:11.

no, it's not 10/11, it's 72/79.

i really have to ask everybody to read the sticky about aspect ratio at the top of this forum and the documents linked therein before posting any more (wrong facts) on this topic. thank you!

wef.

[DVDHack]

I've read all the stuff on aspect ratios in the various threads but they are generally excellent on aspect ratio but don't pull together DivX, aspect ratios and settings for encoding.

I have concluded the following after a weekend of experimentation.

Modern DVDs are 720x576 with no border unless the content is not 16x9 or 4x3. eg borders are added for wider formats than 16x9, but then only for the difference to 16x9.

DivX doesn't get recognised by DVD players as anamorphic so the player does not stretch them horizontally. So people encode with DivX by compressing the verticle and adding the borders. This is fine for both 4x3 and 16x9 TVs. However in a 16x9 TV the display device needs to expand the display in the vertical to eliminate the black lines and the horizontal is expanded to also fit the display.

If you encode at 720x576 the vertical is stretched when displayed on a 4x3 device. When displayed on a 16x9 device only the horizontal needs to be stretched (which it was designed to do in the first place), the vertical is fine as provided.

To get the best quality from a DVD to DivX it appears best to encode at 720x576 and then display it on a true 16x9 device in cases where you are able to use the full resolution (the device will do the stretch in most cases). If displaying on a standard definition TV this all doesn't matter because the resolution is so low.

An alternative that works for everyone is to encode at 1024x576 which leaves the expansion up to the encoded source rather than the device but that would require much greater space but it will be the correct aspect ratio. I'll try this just for interest and report back.

[Sgt_Strider]

Hi, I'm interested in this topic as well because I want to do my dvd encodes and maybe one day be able to view it on a 16x9 TV with no possible problems. I haven't read anything about what resolution I should encode at to best view it on a 16x9 TV and ppl often tell me to crop before encoding. My question is by cropping out the black bars, won't this affect the video when its being viewed on a TV? Sorry for my noob questions but this has been bothering me for a long time now...

[TheWEF]

Originally posted by DVDHack
I have concluded the following after a weekend of experimentation.

i'm sorry that i have to say that, but almost everything you wrote is not true.

i really don't know what to do... :confused:
we wrote the sticky, we provided all the links, we've been discussing forever - still so many are getting it wrong.

my last advice: forget everything you think to know, forget 16:9, forget 4:3, just try to understand the concept of pixel aspect ratio.

most importantly read and understand this document:
Quick Guide to Digital Video Resolution and Aspect Ratio Conversions (http://www.uwasa.fi/~f76998/video/conversion/).
everything there is to know is in there.

wef.

[DVDHack]

By all account, reading is easy, understanding seems somewhat more difficult to achieve.

I can't see anywhere how it can be an advantage (justification) for reducing the resolution of a source so dramatically as you do with DivX in Gordian. I just want a way of ensuring the resolution retains integrity for my later acquisition of a high resolution device. I may need to continue coding in MPEG2/DVD format rather than MPEG4.

[TheWEF]

Originally posted by DVDHack
I can't see anywhere how it can be an advantage (justification) for reducing the resolution of a source so dramatically as you do with DivX in Gordian.

with gknot you can reduce or even enlarge resolution as you like.
i will not talk here about the advantages of adjusting resolution in relation to filesize, bitrate and compressibility. and i do not think i have to justify anything.

however, i think you have to admit, that this has nothing to do with aspect ratio and/or how to get correct aspect ratio when resizing dvd material (the topic of this thread).

you have to understand that, as a moderator of this forum, i simply can not ignore a threads "final" ("I have concluded the following after a weekend of experimentation") post that is full of wrong facts. many people are reading this and i have to point them in the right direction.
i was trying to help.

admitting that "understanding seems somewhat more difficult to achieve" your retort seems hardly justifiable to me.

wef.

[DVDHack]

The update to my thread was not intended to be final, only an update of what I had found in experimenting with encodes over the weekend. It was exactly what I said, conclusion I had drawn from my experiments and I posteed it to draw comments on the merit of this discovery.

My last reply was to advise that I had indeed read what had been posted but failed to understand the finer points.

To me resolution has everything to do with encoding in DivX and Aspect ratio is a parameter in determining that encode. What I am seeking is a setting that will provide both the correct aspect ratio and retain the original resolution. I want to upgrade to a video projector which will use the better resolution available in the source which is lost if I achieve aspect ratio by sacraficing resolution.

Justification is in reference to the broader process and a questioning of the wisdom employed in encoding using a tool without (in my case) understanding the end product. It's not a personal attack. I just want to understand and I get frustrated by being referred to material I have read without me having understood. I will however continue to explore until I do understand, even with a million posts.

[Sgt_Strider]

Originally posted by TheWEF
i'm sorry that i have to say that, but almost everything you wrote is not true.

i really don't know what to do... :confused:
we wrote the sticky, we provided all the links, we've been discussing forever - still so many are getting it wrong.

my last advice: forget everything you think to know, forget 16:9, forget 4:3, just try to understand the concept of pixel aspect ratio.

most importantly read and understand this document:
Quick Guide to Digital Video Resolution and Aspect Ratio Conversions (http://www.uwasa.fi/~f76998/video/conversion/).
everything there is to know is in there.

wef.

I appreciate the link that you have provided. However I didn't really understand the article. The article isn't newbie friendly and I would appreciate if you or anyone that is as knowledgeable as you are to help me.

[TheWEF]

Originally posted by DVDHack
...It's not a personal attack...

all right, i'm sorry if i got this wrong.

Originally posted by DVDHack
...I want to upgrade to a video projector which will use the better resolution available in the source which is lost if I achieve aspect ratio by sacraficing resolution...

what material are you converting to divx, why, and what do you plan to do with it, how do you store it...?

it seems to me that you want to backup dvds careing about quality and nothing else. if that's the case i suggest that you do not reencode at all. get a dvd-recorder. if the original is a double-layer dvd there is a way to split it into two dvd-rs.

Originally posted by Sgt_Strider
...I would appreciate if you or anyone that is as knowledgeable as you are to help me....

i will try, but you have to ask a precise question and tell me exactly what you want to do.

wef.

[Sgt_Strider]

Originally posted by TheWEF
all right, i'm sorry if i got this wrong.



what material are you converting to divx, why, and what do you plan to do with it, how do you store it...?

it seems to me that you want to backup dvds careing about quality and nothing else. if that's the case i suggest that you do not reencode at all. get a dvd-recorder. if the original is a double-layer dvd there is a way to split it into two dvd-rs.



i will try, but you have to ask a precise question and tell me exactly what you want to do.

wef.

Basicly I'm asking you what resolution should I use to encode my divx/xvid encodes in order to watch it on a 16x9 TV. By cropping out the bars, doesn't that essentially destroy the 16x9 image?

[DVDHack]

I'm trying to get two DVDs onto one DVD-R at best quality to play back on a high resolution 16:9 display eg a projector.

I only have a standard 4:3 TV at the moment but want to be a bit upgrade proof given the effort involved.

[TheWEF]

Originally posted by DVDHack
I'm trying to get two DVDs onto one DVD-R at best quality to play back on a high resolution 16:9 display eg a projector.

I only have a standard 4:3 TV at the moment but want to be a bit upgrade proof given the effort involved.

i think DivX is not the right format for you, the main goal here is high compression, saving storage space and bandwidth.

since you can afford a projector i suggest you put one DVD on one DVD-R, probably the easiest way is to use DVD2one.
you'll have very good quality and you can play the discs with any computer/dvd-player on any display/projector you want.

in some problematic cases you can put one DVD on two DVD-Rs to 100% keep the original quality. you can use ifo-edit for that.

Originally posted by Sgt_Strider
Basicly I'm asking you what resolution should I use to encode my divx/xvid encodes in order to watch it on a 16x9 TV. By cropping out the bars, doesn't that essentially destroy the 16x9 image?

are you using a computer with tv-out for playback?
i guess you just have to set your tv for 4:3 and zoom in, that's all.
you could also encode all your stuff anamorphic (just select "non anamorphic" for anamorphic stuff), but i do not recommend that for compressibility reasons.
in any case you should definitely crop the black bars, framesize should be adjusted to compressibility just like the guides explain it and has "nothing" to do with your playback device.

wef.

[DVDHack]

I wish I could afford a projector now. It might be a bit away yet.

I think you may be correct. I currently do DVDs by re-encoding the main movie with CCE and authoring them with scenarist or maestro but the DVD-R costs are still high and the quality poor. I thought I could retain the quality and increase compression using MPEG4 instead of MPEG2 thereby getting two DVDs onto one DVD-R. I have a DVD player capable of MPEG4 (KiSS).

I will do some more playing but at this stage I will stay with CCE and DVD-R.

Thanks for all your help

[Sgt_Strider]

Originally posted by TheWEF
i think DivX is not the right format for you, the main goal here is high compression, saving storage space and bandwidth.

since you can afford a projector i suggest you put one DVD on one DVD-R, probably the easiest way is to use DVD2one.
you'll have very good quality and you can play the discs with any computer/dvd-player on any display/projector you want.

in some problematic cases you can put one DVD on two DVD-Rs to 100% keep the original quality. you can use ifo-edit for that.



are you using a computer with tv-out for playback?
i guess you just have to set your tv for 4:3 and zoom in, that's all.
you could also encode all your stuff anamorphic (just select "non anamorphic" for anamorphic stuff), but i do not recommend that for compressibility reasons.
in any case you should definitely crop the black bars, framesize should be adjusted to compressibility just like the guides explain it and has "nothing" to do with your playback device.

wef.

I was thinking about doing something like an htpc. I don't have a 16:9 TV yet but I probably will sometimes in the future. Will there be any difference in how I should do it?

[Benji99]

Sorry for bringing back a somewhat old thread...

I want to do the same thing as the others here. I want to store DVDs in the best quality possible. Converting a dual-layered moving onto one DVD-R will result in a sure and fairly obvious quality loss (Depending on the movie of course). I'm not keen on the idea of splitting a movie on 2 discs.

So I wanted to store 1 movie per DVD-R, keep the original DTS/AC3 tracks and looking for the best way to re-encode the Video stream into XVID (is what I seem to be leaning on).

Basicly I figure, I should get better quality from a 4gb+ XVID video file then from a 4gb+ MPEG2.

So I also want to make sure I'm future proof and able to get near perfect quality off a future 16x9 tv or projector.

So is XVID/DIvx still NOT recommended for projected use?
Thanks in advance

[DVDHack]

I decided on MPEG2 using CCE to encode. I actually put two DVDs on one DVDR, the quality is excellent - for a favourite new movie I might use a whole DVDR but only if the movie was very long. I'd use DivX if it had an aspect marker but currently you need to encode at an odd resolution to maintain the aspect ratio on a HW device.

It depends on what HW you will play back on, I was using a KiSS HW DivX which couldn't tell it was an anamorphic source and consequently you got a cone head view on it. Reducing the verticle resolution to display in 16:9 resulted in something that wouldn't play back well on a large resolution - you need all the lines you can get !!

If you use a home theatre PC its not a problem - do a 1:1 encode and keep the resolution but use the player to get the aspect ratio correct. The Xbox plays it back well through the XBMP (note the box needs to be modded)

Try CCE first - you might be pleasantly surprised.

Hope this helps.

[Benji99]

Yeah I do plan on exclusively using a PC to play the files or the Xbox (XBMP is indeed very impressive) and finally I'll probably never use one of those cheap H/W divx players (since my xbox can do all that and much more).

BTW, what did you mean do a 1:1 encode? I can't really do that, GK Knot keeps insisting on changing the output video, guess I have to live with that.

Actually, if I had to choose between a resolution slightly higher then the input rather then one slightly lower. And I want to keep the resolution as close to source as possible, would it make sense to choose slightly higher? especially since the W% is always higher then the H%, so if I choose a higher then source W%, that brings the H% Closer to 100%. And I also look for as close an aspect ratio as possible.

Anyways in any case, the ripping I'm working on has an average bit rate of 2977kbits/sec, so I'd be very surprised to see any flaws in the video.

Oh one last thing, considering the very high bit rate, does any suggest any modifications to the "newbie" settings posted for XVID guides? For example, is it still worth it to do two passes?

Thanks again for your time
Benji99

[DVDHack]

In GK change the aspect ratio to 1:1 instead of 16:9 and you will be able to do a re-encode at the source aspect ratio instead of needing to fiddle about with the resolution. The Xbox handles this mode very well - you just set it to an anamorphic source and it does the rest (correct the aspect ratio).

I've got questions about the mpeg4 coding. I have yet to find out if mpeg4 only has a quality advantage over mpeg2 when you choose a lower bit rate? I find that my mpeg2 encodes at a high resolution appear better than mpeg4 at high rates - but mpeg4 looks a lot better at lower bitrates than mpeg2. I need to do some more research. I was hoping that someone with more skills than I would do a comparison of the say CCE and DivX at various bitrates but I haven't seen one.