Anamorphic DivX movies. Possible or bad idea?

[Beastie Boy]

Lets suppose you wish to archive that really special movie and want to preserve all the detail of the original source. Any amount of downsizing prior to encoding will inevitably remove picture detail, no matter how it is performed. Period.

So, if we wish to make a backup that is truly as good as the original DVD quality then we are forced to encode at a resolution that is *** x 576 high (PAL).
If this movie was PAL anamorphic then to achieve the correct aspect ratio, the frame size would need to be 1024x576 pixels (16:9), which would result in massive file sizes.

Now suppose the player knew that the aspect ratio of the movie was 16:9, even though it was encoded at 720x576, we have saved a lot of data without sacrificing any image information from the original. ie anamorphic DivX movies resized at playback.(Hardware resizing is very, very good).

With the advent of huge HDD and cheap DVD-Rs, then even encoded at high bitrates, it would still be possible to fit 2-3 high res movies on one disc. Then we would truly have DVD quality backups.

I believe RV9 has this type of feature but I don't know how it is implemented. Would it simply be possible to modify the file header, or does it need working into the DivX codec?

Any thoughts?

Cheers, Beastie.

[KpeX]

1. IMO you're worried way too much about loss of quality due to resizing. Use a nice sharp resizer like Lanczos and I very highly doubt you'll notice in quality difference purely from the resize, assuming a sane target resolution. Also don't forget you should be cropping black borders. There's no reason to waste bits on them.

2. There are two ways that I know of to encode anamorphically: encode in any format at the anamorphic size and resize with a player that is capable of it, i.e. BSPlayer, Zoom Player, Media Player Classic, probably others. AVI as a container does not support anamorphic. Matroska does support anamorphic encoding, see the new A/V formats forum for more information. In this case you'll also need to use a player/filter that supports it ATM. hth,

[jggimi]

I have done this with short segments, at 100% quality, just as experiments. You can either edit the .avs to remove the resizing filter, or set the PAR to 1:1 and adjust resolution manually.

You'll need to use a player that can display at the intended DAR, as KpeX described.

[Zhnujm]

I have encoded a lot of anamorphic AVIs (DVB or DVD source), you WILL see the quality difference at least if you use a 16:9 TV/Display. No doubt about that.

[Beastie Boy]

Now that cheap DVD+/-R media has arrived, quality no longer has to take second place to file size. There is sufficient storage space to preserve the information in the original. I realise that the only way to truly do this is to make a direct copy, but most movies simply won't fit onto 1 disc, hence the need for MPEG4.
But if we have enough space, why downsize?

What is needed is native support in the codec/container so that any player would play the file back at the correct AR, maybe even a standalone player in the same way as a DVD player outputs the original.

KpeX, I didn't realise that Matroska was capable of this. I shall read up on it. And I would never encode the black bars :)

jggimi, what were your conclusions from the experiments. Do you feel that it would be worth the extra encoding time if file size was not an issue?

Zhnujm, you are clearly someone who strives for quality :D

Cheers, Beastie.

[hakko504]

Originally posted by Beastie Boy
What is needed is native support in the codec/container so that any player would play the file back at the correct AR, maybe even a standalone player in the same way as a DVD player outputs the original. This is indeed supported by MPEG-4, but neither XviD nor DivX has so far chosen to implement this feature.

Just thought that I'd mention that I encode a lot of 4:3 movies anamorphic at the resolution of 352x288 and use zooplayer to correct the AR when I watch it on the monitor.

[SeeMoreDigital]

Hi Beastie Boy

So, if we wish to make a backup that is truly as good as the original DVD quality then we are forced to encode at a resolution that is *** x 576 high (PAL).If this movie was PAL anamorphic then to achieve the correct aspect ratio, the frame size would need to be 1024x576 pixels (16:9), which would result in massive file sizes.
The file sizes don't have to be any bigger at all!

I carried out some tests a few months ago using the PAL version StarWars 1. I encoded the movie 4 times using DivX5.0.5 2pass VBR with Mp3 audio @ 64kbps.

At 720x576 @ 680kbps the finished file size was 700MB
At 1024x576 @ 680kbps the finished file size was 700MB
At 720x576 @ 2040kbps the finished file size was 1920MB
At 1024x576 @ 2040kbps the finished file size was 1920MB

Both the 720 and 1024 encodes playback fine on a PC using say, WinMedia player 9. And I would have to say that high motion scenes looked better at 1024x576 @ 680kbps than at 720x576kbps @ 680kbps!

It was much the same story with the 2040kbps encodes too!

The only downside for me is that my Xcard (hardware TV output card) can't playback smooth video at resoulutions (image pixel frame sizes) above 720x576. However it will allow me to view stills. And the stills at 1024x576 @ 2040kbps look amazing!

Now, when I carried out the same experiment with an NTSC version of the DVD the 720x480 encodes played back okay. But the 848 or 854x480 encodes generated a vertical white noise bar to the right of frame that would not go away..... So no joy for you NTSC guys!

Hope this info helps?

Cheers

[Wilbert]

This is indeed supported by MPEG-4, but neither XviD nor DivX has so far chosen to implement this feature.
ChristianHJW told me once that this feature is implemented in XviD. We just have to wait till vdubmod adds a setting for this.

[SeeMoreDigital]

I generate just about all my encodes at 720x576 anamorphic. When you install the DivX codec I like the idea of being able to set 'aspect ratio' under the 'decoder properties' when the 'overlay extended mode' option is checked.

This works great when you come to view your DivX encodes using any software player except DivX's own player 2.5!

I find it wierd that with the DivX player 2.5 you still have to set the player to the required aspect ratio, everytime you view an encode

I think it is about time an 'AR check box' was incorporated within a codecs set up options.

Come to think of it. I seem to remember the new version of DrDivX having this function now. I'll have to check!

Cheers

[Beastie Boy]

SeeMoreDigital, those results are interesting.I guess if you encode at a fixed bit-rate then the file size will remain the same but the picture quality would degrade as the frame size gets larger. Which is why I was suprised to read that your encodes looked better encoded at 1024x576 rather than 720x576.
However, I don't think I want to spend the extra bits (or encoding time) encoding the full 1024x*** resolution when in theory, I am not adding anything that isn't there in the 720x*** original.

The XviD option is interesting although I have only ever used DivX and am pleased with the quality. Perhaps it's time for a change.

I did a couple of test clips encoded at 720x576 @2300 kbps (calculated to fill half a DVD with the AC3 track included) and the quality on playback was simply superb.
I original tried 1 pass quality based in an effort to offset the increased encoding time, but the file size was larger than I predicted.
I then went for 3 passes, standard speed which gave an average quantiser of 3.8 and the quality really was as good as the original. Encoding speed was approx 6-8 fps on a 2.6 Ghz P4, hence slow speed was not used (I'm not that patient).

The DivX Player is not that good at playing back the files. If you select the 16:9 ratio it plays back at the correct AR, but compresses the window vertically rather than stretching it horizontally. If I wanted this, then I wouldn't have bother encoding at this size!
Playback is also demanding. With full post processing applied, playback was really jerky. With the ATI hardware support, there were no problems.

I am now considering encoding all my movies at full res at a bitrate to fill half a DVD and storing them on my HD until I buy a DVD writer. The cost of a DVD will soon be the same as 2-3 CDs but the quality is way better with all the original info captured.

Try it, you might like it.

Cheers, Beastie.

[SeeMoreDigital]

SeeMoreDigital, those results are interesting. I guess if you encode at a fixed bit-rate then the file size will remain the same but the picture quality would degrade as the frame size gets larger. Well, all my encodes are 2 pass VBR (variable bit rate) not CBR (constant bit rate) or "fixed bit-rate" as you describe! If you use the 2 pass VBR method of encoding you will only usually see degraded frames when the onscreen action gets very busy. Or when you encode at low bitrates!

Which is why I was suprised to read that your encodes looked better encoded at 1024x576 rather than 720x576. Yes, this is certainly a strange one. When I first thought about encoding at 1024x576 'full frame', I was not expecting the image to look any different from the 720x576 'anamorphic' encodes. But the evidence is clear. When the horizontal resoulution is increased by 42%, high speed images do indeed look better!

I believe that some RV9 users encode PAL DVD sources at 1024x576 too!

I did a couple of test clips encoded at 720x576 @2300 kbps (calculated to fill half a DVD with the AC3 track included) and the quality on playback was simply superb.
I original tried 1 pass quality based in an effort to offset the increased encoding time, but the file size was larger than I predicted.
I then went for 3 passes, standard speed which gave an average quantiser of 3.8 and the quality really was as good as the original. Encoding speed was approx 6-8 fps on a 2.6 Ghz P4, hence slow speed was not used (I'm not that patient). If you want speed and you're encoding at around 2000kbps. Use the DivX 'standard' setting with no BiDi, Qpel, GMC etc and write an MV file for your second pass. If you use this method, you first pass should be around the DVD's run time and the second pass should be quicker still!

The DivX Player is not that good at playing back the files. If you select the 16:9 ratio it plays back at the correct AR, but compresses the window vertically rather than stretching it horizontally. If I wanted this, then I wouldn't have bother encoding at this size! This is how all the software players work, when displaying a 720x576 encoded image on a 4:3 PC monitor!

Playback is also demanding. With full post processing applied, playback was really jerky. With the ATI hardware support, there were no problems. It's a known fact that there are problms with DivX 5.1.0 post processing. Even I have problems with my P4 2.8 processor at home and twin P4 3.06 processor setup at work! There are no reported problems with hardware decoders!

I am now considering encoding all my movies at full res at a bitrate to fill half a DVD and storing them on my HD until I buy a DVD writer. The cost of a DVD will soon be the same as 2-3 CDs but the quality is way better with all the original info captured. Not a bad idea. 2 pass VBR encoding above 2000kbps should look excellent. 1 pass CBR encoding at 2000kbps will not look so hot when the action speeds up. You could need as much as 4000kbps for such scenes!

Cheers

[Beastie Boy]

quote:
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SeeMoreDigital, those results are interesting. I guess if you encode at a fixed bit-rate then the file size will remain the same but the picture quality would degrade as the frame size gets larger.
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Well, all my encodes are 2 pass VBR (variable bit rate) not CBR (constant bit rate) or "fixed bit-rate" as you describe! If you use the 2 pass VBR method of encoding you will only usually see degraded frames when the onscreen action gets very busy. Or when you encode at low bitrates!


Sorry, this was a poor choice of phrase on my behalf. What I meant to say was encoding with a target bitrate will always yeild the same file size. 1 Pass Quality based could give a good indication as to the extra bitrate required.
Downsizing the movie will also affect it's compressibility as some noise is also removed along with the details. Therefore, it may also be necessary to apply noise reduction for a full res encode where as otherwise you wouldn't.

With regard to player, I seem to recall that ZoomPlayer has an option to store the aspect ratio for all the movies it plays so that the correct aspect ratio would be shown each time without further adjustment. I shall look into this.
I still haven't yet found how to encode/transfer movies to the Matroska format with anamorphic playback yet. More digging required.

Cheers, Beastie.

[SeeMoreDigital]

Beastie Boy,

What encoding application do you use?

Have you generated many 2 pass encodes?

PM me if you like!

Cheers

[dTb]

I've been encoding retaining the anamorphic dar for a while now because I watch all my movies on a widescreen tv. Doing it this way retains more vertical resolution and negates the need to stretch the video vertically to fill the screen.

[Beastie Boy]

dTb, what player do you use? Do you resize via the player or let the TV stretch the picture?

I still haven't found any info regarding Matroska and anamorphic encodes. Could anyone point me in the right direction?

Cheers, Beastie.

[dTb]

I use zoomplayer, I have a widescreen tv with vga input. It uses 640x480 for resolution which is effectively stretched horizontally. So if I encode to an anamorphic DAR and select 'source aspect ratio' within Zoomplayer it will display correctly on the tv as it's basically the same as the way a DVD works. I guess it should be similar for tv's requiring the use of a graphics card with video out.
For reference I've started adding an ogm tag with the correct DAR because say I give a movie to a friend with a 4:3 tv it won't display properly.

To find info on matroska do a search for matroska by author ChristianHJW.

[SeeMoreDigital]

Originally posted by dTb
I use zoomplayer, I have a widescreen tv with vga input. It uses 640x480 for resolution which is effectively stretched horizontally.... I have an Hitachi TV with this option. Which was great for watching NTCS DVD's / encodes but sadly not PAL!

Too bad there was never an 768x576 output 'screen resolution'. As it would have made life for us PAL users far more interesting!

Nice to see you around. Cheers.

[Beastie Boy]

dTb, how so you add the DAR flag to theogm file? I'm currently using VDubMod and that feature isn't supported yet.

SeeMoreDigital, are you saying that you would like to set you PC output resolution to 768x576? If so, then the Powerstrip (http://www.entechtaiwan.com/) software could help you to do this. By all accounts it is excellent software.

Cheers, Beastie.

[SeeMoreDigital]

Originally posted by Beastie Boy
dTb, how so you add the DAR flag to theogm file? I'm currently using VDubMod and that feature isn't supported yet.

SeeMoreDigital, are you saying that you would like to set you PC output resolution to 768x576? If so, then the Powerstrip (http://www.entechtaiwan.com/) software could help you to do this. By all accounts it is excellent software.

Cheers, Beastie. Thanks for reminding me about this bit of software. I remember using it 2 or 3 years ago. 'll have to dig it out of our archive and see if it works!

Thanks mate, Cheers!

[symonjfox]

I'm waiting for a True AR implementation since the first time I used DivX 3.11. I searched a lot and discussed this argoment many times.

The good thing is that MPEG4 does support AR flags. So, Xvid dev3 does support it.
The bad thing is that too many people use DivX Xvid streams in AVI container. AVI doesn't support AR flag, I read many pages, there was a kind of hack to let AVI support it, but it's too complicated to be implemented.

So, Matroska and the real MPEG4 container can handle this. Or better Matroska handles it by itself, while in the MPEG4 container, it's the MPEG4 STREAM that has to have this flag.

Yes, you mean that in DVD backup maybe it's easyer to resize & encode. But I usually record from DVB channels, these are 352*576 or 544*576 in many cases. Using these resolutions, you understand that I'd have to resize to 352*240 or 768*576 but in both cases there will be a drastic quality lose. A good anamorphic implementation would be nice, since I just rip & reencode keeping the best quality as possible.

[dTb]

Originally posted by SeeMoreDigital
I have an Hitachi TV with this option. Which was great for watching NTCS DVD's / encodes but sadly not PAL!

Too bad there was never an 768x576 output 'screen resolution'. As it would have made life for us PAL users far more interesting!

Nice to see you around. Cheers.

What's the problem exactly, is it just that the 640x480 res doesn't take advantage of the high resolutions you use? I'm in a PAL territory as well and generally resize to around 640x--- which works very well. The VGA input is far better than using video out from a graphics card, how does the XCard compare?

@Beastie Boy, I just add an extra comment to the ogm and it's only for my reference, it won't get used in any way by a player. It's there so that if I happen to watch a vid on a 4:3 tv I know the right DAR to set in Zoomplayer.

Edit: Try this link Beastie Boy for how to create mkv files with anamorphic resolutions that are resized on playback
http://forum.doom9.org/showthread.php?s=&threadid=54677&highlight=anamorphic+AND+matroska

[Beastie Boy]

@Beastie Boy, I just add an extra comment to the ogm and it's only for my reference, it won't get used in any way by a player. It's there so that if I happen to watch a vid on a 4:3 tv I know the right DAR to set in Zoomplayer.

Good idea. I had started noting them in a text file, but that is much better.
Thanks for the link. alexnoe wrote in this thread (http://forum.doom9.org/showthread.php?s=&threadid=62297) that he will provide support for aspect ratios in AVI-Mux GUI which should be even easier (I prefer GUIs to command lines).

Cheers, Beastie.