how to crop/resize without aspect ratio error

[cd090580]

Hi,
I'd like to convert a DVD PAL to a SVCD but I have a little problem to resize it correcly.
My movie is 16/9 with 2.35:1 format. So How can I resize it with Avisynth.

Do I need to crop the black bars then resize ???

Can I have a sample script ??

Thanks

[DJRumpy]

Without knowing your input resolutions, we can't give you a script to resize. To answer your other question, yes, you should remove all letterboxing before resizing. In your case, your moving to a different format, probably from a 16:9 source, to 4:3 SVCD. You'll need to redo the letterboxing for a 4:3 format.

Open the file in VirtualDud
Frim the Video menu, select FILTERS.
Click the ADD button
Find 'null transform' in the list, and click OK
The cropping button should now be available. Click it.
Increase the Y1 and Y2 offsets until all letterboxing is removed.
Those two values are the values used with the CROP command in AVISynth. You can find some illistrations of this process here: https://www.videohelp.com/forum/userguides/174200.php

[cd090580]

The DVD source resolution is: 720*576 and I want to resize it to svcd at 480*576.

[Dragonsf]

The transformation from 720x576 to 480x576 is done by the mpeg-2 encoder.If your source is anamorphic, you have to set the AR correctly or manually switch your TV into 16:9 mode.

[FOO]

What happens if he just resizes from 720 to 480
and encodes with the same 16/9 DAR,
Won't it then look the same played from a SVCD ?

[Dragonsf]

As we are talking aboout PAL, xxx*480 won't help. 8) (just replace 480 with 576)
But I never tried to encode a 480x576 resized avi with DAR 16:9 (or whatever).It's really worth a try.If anybody else hasn't done that before, I'll try it.Otherwise, please report your findings!

[FOO]

I meant resize from 720 x 480 to 480 x 480

[FOO]

And if you want to get picky, it's not good to
encode the letterboxed picture, The black won't use too
many bits , but the black edge pisses off the DCT

[SquirrelDip]

I'm not sure about SVCD but 1/2 D1 (CVD resolution) doesn't support letterbox. If this is the case then try the following to get the 4/3 resolution:



Then pad 72 top and bottom to bring the resolution back up to 576.

[DJRumpy]

SVCD supports letteboxing. Letterboxing is just a black image area. It would be more accurate to say SVCD doesn't support a 16:9 MPEG aspect ratio flag. Your player may play a 16:9 DAR mpeg, but it's not compliant. You can directly resize a 16:9 720x576 mpeg to 480x576, and place a 4:3 aspect ratio on your SVCD MPEG. What you will get will be a 16:9 aspect ratio contained within a 4:3 MPEG. It will look 'right' on a widescreen television. It will look tall and skinny on a 4:3 television.

If you do not have a widescreen television, you must resize it to a proper 4:3 aspect ratio to have it look 'right' on a 4:3 television.

[FOO]

I would have assumed that IF a player will recognize
the SVCD format it would then hand the MPEG2 stream to
the MPEG2 decoder which would honor the DAR in the
stream header. The decoder will do it for a DVD. Why would
it specifically refuse just because it's a SVCD.

The SVCD info in the Whatis section on this site claims
16:9 support in the SVCD spec.

[DJRumpy]

As I said, many players will play an SVCD with a 16:9 DAR flag, mine included, but it is technically not supported by the SVCD specification. I'm not sure where your reading that SVCD supports 16:9. You may want to recheck your sources. I glanced through the 'What is SVCD' section, but found no reference to supported aspect ratios.

[FOO]

I don't beleive everything I read , but this was out there.

http://www.uwasa.fi/~f76998/video/svcd/overview/#technical_features

where is the real spec ? they probably want money for it.

[Dragonsf]

Here are the Philips specs:
http://www.licensing.philips.com/includes/download.php?id=2698&filename=2450.pdf
(nothing about aspect so far)
or here
http://www.cdrinfo.com/Sections/Articles/Specific.asp?ArticleHeadline=SuperVCD%20Format&Series=0
(againAR is not mentioned)

[buttsy00]

Could you guys please have a look at my post

"https://www.videohelp.com/forum/viewtopic.php?t=181422&highlight=aspect+ratio+wide screen"

and see if anyone can help me.

Any help would be appreciated.

[DJRumpy]

This is kind of bizarre. I went out yesterday and browsed for over half an hour, and could not find any mention of DAR for SVCD (other than FOO's link of course). I'll see if I can find the specs today. I'm only able to find mention of DAR in the MPEG-2 specs, and no mention in the SVCD specs I'm finding. Does anyone know the organization who defined the MPEG-2 specification? It would make the search easier.

[FOO]

these people claim offialdom.

http://www.chiariglione.org/mpeg/index.htm

I read that the Chinese initially came up with it,
and it was adopted.

[DJRumpy]

This is the mpeg standards site, which isn't what we're looking for. Have you had any luck finding the organization who founded SVCD? I did find a specifications document on http://www.labdv.com/leon-lab/video/svcd_en.htm but even the tech sheet (pdf link) doesn't mention aspect ratio. I'm searching the Phillips site now. I'll post if I find anything.

[Dragonsf]

I always thought, Philips was the founder of the SVCD standard (which was introduced by a Chinese consortium).

Anyway, I'll do a test tonight and see what happens.

[FOO]

I think we know it works sometimes. The question is
what the official spec sez. I think I saw it , i'll look.

[DJRumpy]

I know it works on one of my dvd players (the other doesn't support svcd), but I do not know if it works properly with a 4:3 television ( I have a widescreen tv). It may look tall and skinny.

[FOO]

I don't have one. I spoze I could make one .
Would it mean anything to play it with a software DVD player ?
Those assume a "regular" TV don't they.

[FOO]

I have a captured movie lying around.
it was 720 x 480 MPEG2 4:3
I will open in Vdub , crop 60 from top & bottom
and encode with 16:9 DAR at 480 x 480 ,
make a SVCD , mount it on a Daemon fake disk and get WinDVD to play it.

results in a few.

[FOO]

I don't know how to control these players . Win dvd does what it wants
Power DVD if set in "keep aspect ratio" and dragged to 4:3
does a letterbox and looks like a TV displaying a 16:9 DVD.
so what eh ?

[SaSi]

This is the mpeg standards site, which isn't what we're looking for. Have you had any luck finding the organization who founded SVCD? I did find a specifications document on http://www.labdv.com/leon-lab/video/svcd_en.htm but even the tech sheet (pdf link) doesn't mention aspect ratio. I'm searching the Phillips site now. I'll post if I find anything.

I thought that the reason why SVCD is not properly supported by many DVD Players is that it's NOT an official standard. On the other hand, the fact that at least some - or many - players DO support it, means that it emerged from somewhere.

I think it's Phillips who "discovered" it, mainly because the only "proper" authoring program to do SVCD that I've seen comes from Phillips.

[FOO]

There's lots and lots that don't mention the DAR.

This is heresay of course but...

http://www.trevormarshall.com/byte_articles/byte12.htm

I also found some SVCD hardware that would do about any DAR.

[DJRumpy]

SVCD is a true standard, ratified by the chinese government as the replacement standard for VCD. It was developed jointly by China, Phillips, and one other who I can't recall of the top of my head. As for support, most of the newer players support it. The early ones didn't simply because they existed before the SVCD standard was ratified. Support for SVCD seems to be somewhat spotty after that, with all players in China supporting it, with some vendors behind it one hundred percent, while others offer it their high end equipment. Probably due to people like us (home hobbyists), purchasing players due to their supported formats.

As for the aspect ratio, I still haven't found anything concrete. I've seen two posts that mention it can play back animorphic, but it doesn't say that it supports the 16:9 tag (simply resizing a video to 360 vertical (432 pal) will give you a 2.35:1 widescreen, even with a 4:3 DAR. This would not look 'right' on a 4:3 televisoni though). I've also found two references that state it converts the video to 4:3 aspect on playback. Unfortunately, none of the links looks like the know-all of SVCD

The only thing that I found, that was even close, was the MPEG specification itself, specifying anything with 352 lines supported only 4:3 (VCD, and CVD). No mention of 480 horizontal formats like SVCD. What's really strange is that every other specsheet for things like CVD, and DVD are quick to point out what aspect's are supported. I can't find anything on SVCD itself other than vague sentences pointing either way.

FOO, the sofware test wouldn't be a good one. Your software player will tolerate just about anything. It's the standalones that always complain

cd090580, I suppose you should just have to try a 16:9 encoded mpeg, and see if your player tolerated it. I've heard complaints of stuttering video on players that didn't, as well as wrong aspects, and shifted video.

I would do a small clip (on CDRW media if your player supports it). Cropp off your letterboxing, so only image are remains. Resize that to 480x432, and then add letterboxing to pad your vertical from 432 to 576 (576-432=144. 144/2 = 72 top letterbox and 72 bottom letterbox). This is is an anamorphic svcd. Make sure you put a 16:9 DAR flag on the mpeg. If your player supports it, it should automatically letterbox the video. If it does not, it may not play, or the aspect may look wrong on your 4:3 televsion.

If it doesn't play properly, you will need to convert it to a letterboxed 4:3 rather than an anamorphic svcd. To do so, remove any letterboxing, so that only image area remains (use the crop command in AVISynth). Resize this to 480x324, and then add letterboxing to the 324 to fill out the vertical to the full 576 pixel height.

[Dragonsf]

Why do pixel (in PAL land) have a PAR (pixel aspect ratio) of 180/192 (=15/16) ? Anyone knows?

[ronnylov]

Why do pixel (in PAL land) have a PAR (pixel aspect ratio) of 180/192 (=15/16) ? Anyone knows?

Where did you get that from? On a PAL DVD with 720x576 or 704x576 resolution the PAR is 54/59.

Somebody must have been confused. With square pixels you have a 4:3 aspect ratio if you have the resolution 768x576 pixels. This picture is resized to 54/59 of 768 pixels (thats almost 703 pixels width) and then black borders are added to left and right to make the picture 720x576 or 704x576. Both 704x576 and 720x576 formats use the same PAR of 54/59.

"The confused person" must have thought that the 768x576 square pixels were resized to 720x576. 768/720=180/192=15/16.

To make resizing operations easier I recommend using FitCD.

[Dragonsf]

To be more specific:I was talking about DV resolution.