Expert advice needed - Aspect Ratio

[mikeathome]

Hi,

Background:
With Darim MPEG Changer (DVMpeg) you'll be able to change
a) the field order
b) the Aspect Ratio
of a given MPEG Stream.

Q1:
Where's this information stored ? I guess in the MPEG Header of the frames ?

Q2:
Having an anamorph MPEG Video Stream. Patch this with different Aspect Ratio values. Will this influence the final picture scaling
a) while playing only the video stream (e.g. on a PC)
b) after authoring with a DVD Authoring Soft (like Maestro set Video to Letterbox 16:9)

Why do I ask:
I have a strange James Bond Movie (Diamonds are for ever) which has to re-encoded to fit on DVD-R(5). After re-encoding with CCESP via DVD2AVI/VFAPI (CCESP set to DAR 16:9), I have the impression the Aspect Ratio is wrong, the height is somewhat squeezed. I did not do any resize or image manipulation on the way to CCESP. Following settings:
- DVD2AVI shows 16:9 (create Project)
- set DAR 16:9 in CCESP
- set Video 16:9 Letterbox in Maestro

Q3:
Can it be, that the Aspect ratio is already wrong on the Source DVD.

Q4:
Anyway to fix that (by patching and/or re-encoding with a resize/crop combination) ?

mike

[tom para]

I d/o have the specifc answers but here's what I went thru. I'd tried out every DAR configuration in Darim MPEG Changer a while ago and quit: the output is always rejected by scenarist, spruce and a bunch of other apps. It could be that Changer's MPEG output is good for generic PC playback but not necessarily MPEG for DVD.

Anamorph stuff works like an accordion. Squeezing at storage and unsqueezing on playback. That means the player & TV will have to be configured similarly. Check everything from source to final devices. Trying different scaling tricks via header has never worked for me.

It could be that Diamonds has already been letterboxed and encoded as 4x3. The best way I've found to check aspect ratio is to DVD2AVI a piece of the video, load the AVI into VirtualDub and study it before proceeding w/ the rest.

Pls let us know what you find out. Thanks.

[tyee]

Hi mikeathome

I don't know if this will help, but setting "16:9 Letterbox" in Maestro adds this flag into the mpeg stream that tells either your software player or hardware player to vertically squeeze the image to the display device. I have only selected this "16:9 Letterbox" switch in Maestro when I have anamorphically encoded via CCE (4:3 A/R). So I think what's happening is that CCE is vertically compressing the original anamorphic video to 16:9 (for a 4:3 display device), and then Maestro is again telling the playback hardware/software to compress again. Try leaving Maestro at 4:3 and see what happens, OR do the following -

If any disc is anamorphically encoded 16:9, I always encode at 4:3 with CCE, and then in Maestro add the "16:9 Letterbox" switch, which allows proper A/R playback on both a 4:3 or 16:9 monitor.

tyee

[mikeathome]

Hi,

thx. for the answers.

Originally posted by tyee
Hi mikeathome

I don't know if this will help, but setting "16:9 Letterbox" in Maestro adds this flag into the mpeg stream that tells either your software player or hardware player to vertically squeeze the image to the display device. I have only selected this "16:9 Letterbox" switch in Maestro when I have anamorphically encoded via CCE (4:3 A/R). So I think what's happening is that CCE is vertically compressing the original anamorphic video to 16:9 (for a 4:3 display device), and then Maestro is again telling the playback hardware/software to compress again. Try leaving Maestro at 4:3 and see what happens, OR do the following -

What ???, I would swear CCESP nether does any resize (or what else is meant by vertical compression !)
This is an interesting thought, I'll check that with the original again. That would explain why I found a few DVDs out there, where the VOB is shown as 16:9 and than the elementar video stream (after demuxing) is 4:3 using DVD2AVI. Although I can't believe it, I'll check definately.
I did switch of Hardware Player 'compression' (Pioneer 444) by settings it to 16:9 and left the TV in 4:3 mode. That should approximately come to the same effekt than authoring in 4:3, shouldn't it ? The image is vertically stretched in this mode.
In Pioneer 4:3 mode the player compresses the video for playback in correct aspect ratio on a 4:3 TV, in 16:9 mode the player sends 12V to pin 8 on scart when playing 16:9 content to have the TV switch to 16:9. Both works with my TV.

If any disc is anamorphically encoded 16:9, I always encode at 4:3 with CCE, and then in Maestro add the "16:9 Letterbox" switch, which allows proper A/R playback on both a 4:3 or 16:9 monitor.
tyee

I did a quick check yesterday (quick, ha, took me 2 hours...). I copied the DVD-R(5) on the HD and demuxed it. Than patched the stream to 4:3 with Darim MPEG Changer (DVD2AVI recognises it now as 4:3; before was 16:9) and re-did the Maestro Project (I always copy the project files, like menues etc.). There's absolutely no difference while playback. Same strange aspect ratio.

While writing this, I am absolutely sure I ALWAYS encode 16:9 in CCESP when DVD2AVI shows 16:9 while creating the project. I never had any of this strange behavior always comes out correct. But I remember, most of the time than the elemenatry video stream (after demux w/ Vstrip) shows 16:9 as well, only on this very rare cases, like JB-Diamonds, I remember that the elementar video stream shows magically 4:3.

This let me come to the conclusion that this only a flag which can't have an influence at all...

... well, I may have to reconsider and re-encode a few videos, oh, shit what a nightmare...

cu, folks (or may be I am off for a few weeks :-(((((

[mikeathome]

Hi,

got the answer to myself:

1) It doesen't make any difference whether you encode 4:3 or 16:9 in CCESP. He does NOT change any Aspect Ratio.
2) JB 007 - Diamonds are forever Region 2 has been mastered at wrong aspect ratio. A circle (the gun at the beginning of each JB) on the original DVD is 15cm wide by 13cm high on my TV set to 16:9 mode (huh, I was not aware of the fact that James fires oval bullets; may be a new trick of Mr. Q ;-). If you set the TV to 4:3 it is definately stretched in height, so no circle either. Since a vertical strechted picture looks even worth you have to live with the first. So be aware of that if you consider to purchase that title.
I'll drop a note to the mastering company!
3) You set the aspect ratio of the DVD with the Authoring program. For all anamorph titles 16:9 Letterbox is the right choice.
4) If the original video stream is in wrong aspect ratio you'll end up with wrong aspect ratio on the encoded content as well. NO WAY to fix that with any type of patching. If you want to fix that you have to re-encode AND RESIZE the video to the right aspect ratio. In the moment I do Diamonds. How: I cropped of 44pixel at the top and bottom and did a bicubicresize to 720x576. That gives an exact circle when the video stream is authored to a 16:9 Letterbox title.
5) If you don't resize when you do a backup of a given DVD, your aspect ratio will stay the same!!!

regards, mike

[tyee]

thanks for sorting it out mike

tyee