Welcome to Doom9's Forum, THE in-place to be for everyone interested in DVD conversion.

Before you start posting please read the forum rules. By posting to this forum you agree to abide by the rules.

 

Go Back   Doom9's Forum > Announcements and Chat > General Discussion

Reply
 
Thread Tools Search this Thread Display Modes
Old 17th May 2012, 07:18   #1  |  Link
hunter_aran
Registered User
 
Join Date: Nov 2011
Posts: 37
Weird Mediainfo, cropping, aspect problem...

I didn't know where to put this so Mods please feel free to move it where it should go...

First of all, I want to say this forum is awesome and a constant source of knowledge and learning! So for you guys tolerating my questions, I really appreciate your time.

I've been on this aspect ratio quest for the last few months, running into various problems. Thought I had everything figures out... Anyway, my latest issue happened when I started using the MuldeR's Simple x264 Launcher. Amazing program, check it out if you haven't already! Well I thought there might have been a bug in it because I thought it was the only thing that changed in the batch of files I was working on. Well I found out by trial and error that in fact it had to do with anamorphic files that are not cropped and Mediainfo's report.

What happens is that I have a h264 file in a Mp4 container at 720x480, ending up at 640x480. The SAR (or PAR if you like) is set at 8:9 in the stream and the container has the same ratio set at 8:9 and display resolution of 640x480. So everything looks fine and dandy. Well I pop it in to Mediainfo and it gives me two lines of "display" and "original" aspect ratio. Both lines say 4:3 but I've been told that when both lines appear, it means that the container and stream ratios don't match. Aargh!

Well I encoded one of these messed up files again, this time cropping 4 off the bottom and behold the Mediainfo window says the aspect ratios are the same! Why did the non-cropped one have a discrepancy and not the same one cropped? Any ideas...? Is this that ITU thing I don't understand?

I used either MTR or DVDFab vob passthrough (for tough encryption) for copying the files, DGindex, Avisynth, Simple x264 Launcher, and finally Subler to set the container display info. Worked correct before...
hunter_aran is offline   Reply With Quote
Old 18th May 2012, 06:58   #2  |  Link
hello_hello
Registered User
 
Join Date: Mar 2011
Posts: 4,002
Quote:
Originally Posted by hunter_aran View Post
Well I encoded one of these messed up files again, this time cropping 4 off the bottom and behold the Mediainfo window says the aspect ratios are the same! Why did the non-cropped one have a discrepancy and not the same one cropped? Any ideas...? Is this that ITU thing I don't understand?
Someone else may be able to give you more exact information, but as long as MediaInfo says the original and display aspect ratios are the same I don't think there's anything to worry about.
I've seen the same thing from time to time (MediaInfo showing both original and display aspect ratios which are the same), even though there is only one display aspect ratio.

What I suspect happens is sometimes the aspect ratio written to the video stream and the container aspect ratio are stored differently even though they're the same. ie one may be 4:3 while the other is 640x480 (or something similar) and for some reason MediaInfo sees them as being different so reports both, even though in the end it reports them as being the same.

MediaInfo also "rounds" the aspect ratio quite a bit. It seems to report standard aspect ratios (4:3, 16:9, 2.35:1 etc) and everything in between gets "rounded" to the nearest "standard". For instance I just checked a 704x384 AVI which has an aspect ratio of 1.8333:1 but MediaInfo reports 1.85:1.
So it's probably some combination of the way the two aspect ratios are written and the way MediaInfo rounds them which causes it to sometimes show original and display aspect ratios, while sometimes only showing a display aspect ratio, but as I said I've seen it happen plenty of times before (in fact the third anamorphic MKV on my hard drive I checked with MediaInfo showed two display aspect ratios which are the same) so whatever the reason it happens, I'm sure it's nothing to worry about (unless of course MediaInfo reports the original and display aspect ratios as being different).

PS It wouldn't have anything to do with ITU vs non ITU resizing. That's a choice on how to resize a DVD for playback. The "official" ITU resize methods aren't exactly 4:3 or 16:9, however in my humble opinion most DVDs don't use ITU resizing. The encoded video will have a specific aspect ratio after cropping regardless of the resize method used when encoding, only the aspect ratio will be slightly different depending on which resize method you use, but either way it's not the reason for MediaInfo sometimes reporting the aspect ratio twice.

Last edited by hello_hello; 18th May 2012 at 07:12.
hello_hello is offline   Reply With Quote
Old 18th May 2012, 19:06   #3  |  Link
hunter_aran
Registered User
 
Join Date: Nov 2011
Posts: 37
That is helpful! I kinda wish Mediainfo was a little smarter and understood that the aspect ratios being written differently really meant the same thing. I opened one of the files in Mediainfo in debug mode and saw the details: there are now two lines that say "original aspect ratio" and two for "display aspect ratio". "Original" says 4:3 and 1.334, "Display" says 4:3 and 1.333. So one is being displayed rounded which seems to be the difference... ok. So I guess when the sar 8:9 is written in the stream, it gets rounded and when it's the one in the container it's not. Well I guess there really is nothing to worry about then.
hunter_aran is offline   Reply With Quote
Reply

Tags
aspect ratio, dar, mediainfo, par, sar

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +1. The time now is 01:01.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2019, vBulletin Solutions Inc.