Aspect Ratio

Discuss about generic usage of MediaCoder.

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stanley
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Post by stanley » Wed Jul 26, 2006 10:04 pm

I've fixed the aspect issue. An update will be released soon.

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adlermike1
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Post by adlermike1 » Thu Jul 27, 2006 8:38 am

Glad you found the issue and look forward to giving a try!

I will watch for a new update.

Thanks again for your efforts.... :lol:

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Post by adlermike1 » Sat Jul 29, 2006 4:40 am

Tried a few more tests with build 2338.

16x9 VOB input

Test1: ensured all "PICTURES" checkboxes NOT selected.

1. Output created says Aspect ratio 16/9 in MediaCoder ("Item/Details of Selected File").
2. Plays back on MemPlayer OK!
3. "AVICodec" program shows file as 4:3!
4. Fileplays back in Windows Media Player as 4:3!

Test2: select "PICTURES/Aspect Ratio" & set as 16:9.
Same exact results as Test#1.

Any ideas why files only play correctly using MemPlayer, and not Media Player, Nero Player, or even AVIcodec information?? Must be some kind of setting in the file, or MemPlayer is only player that detects correctly...

Confused!



:cry: [/u]

stanley
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Post by stanley » Sat Jul 29, 2006 11:21 am

What's your target video format?

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Post by adlermike1 » Sun Jul 30, 2006 6:13 am

Target is XVID...(details above)

Maybe I am just missing the correct settings to take a VOB that is NSTC 720x480 resolution (with DAR=16:9), to an XviD file with 16:9 aspect ratio.

I am concerned I may not understand correct settings. Anyone willing to provide a 1-2-3 step list to see if I got it right??

...frustrated...but hopefully learning...
:cry:
Last edited by adlermike1 on Mon Aug 07, 2006 9:33 pm, edited 1 time in total.

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Post by adlermike1 » Sun Jul 30, 2006 11:45 pm

Found this info on the MemCoder site.
===============================================
12.9. Preserving aspect ratio
Chapter 12. Basic usage of MEncoder


DVDs and SVCDs (i.e. MPEG-1/2) files contain an aspect ratio value, which describes how the player should scale the video stream, so humans will not have egg heads (ex.: 480x480 + 4:3 = 640x480). However when encoding to AVI (DivX) files, you have to be aware that AVI headers do not store this value. Rescaling the movie is disgusting and time consuming, there has to be a better way!

There is

MPEG-4 has a unique feature: the video stream can contain its needed aspect ratio. Yes, just like MPEG-1/2 (DVD, SVCD) and H.263 files. Regretfully, there are few video players apart from MPlayer that support this MPEG-4 attribute.

This feature can be used only with libavcodec's mpeg4 codec. Keep in mind: although MPlayer will correctly play the created file, other players may use the wrong aspect ratio.

You seriously should crop the black bands over and below the movie image. See the man page for the usage of the cropdetect and crop filters.

Usage

Code: Select all

mencoder sample-svcd.mpg -ovc lavc -lavcopts vcodec=mpeg4:mbd=2:trell:autoaspect -vf crop=714:548:0:14 -oac copy -o output.avi
===============================================

Seems to explain why my file plays correctly in MPlayer, but not other players. DAR flag is being respected and resizing correctly, but ONLY in MemPlayer. I think that means my efforts to "resize" NTFS DVD (720x480) to fit 16:9 aspect ratio is not working.

Any I missing something? Can anyone provide proper steps in MediaCoder to RESIZE an NTFS DVD (720x480) to fit 16:9 (1.8aspect)??

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Finally --- Success!!

Post by adlermike1 » Mon Jul 31, 2006 1:33 am

I found that if I RESIZE Picture to 624x352, and don't mess at all with the SETTINGS dialog (browser part), I get the results I want.

So, a 720x640 NTSC DVD file, with DAR=16:9, needs to be RESIZED to 624x352 to get the 16:9 aspect ratio correct. Using the "Aspect Ratio" checkbox does not work...

Any way for MediaCoder to read the DAR flag in the VOB and automaticaly determine proper Video RESIZE to use for encoding?

This is what MPlayer and any DVD player do. I found that programs like AVS Media do this automatically also. Does this feature exist in MediaCoder and I just missed it?

Also, it there any way to pick your own specific Video Height and Width for Resize? RESIZE picklist has limited options...

Finally making progress. Any help appreciated... :lol:

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Post by adlermike1 » Sun Aug 06, 2006 6:07 am

If I transcode the same file using Dr. DivX, it automatically handles re-sizing (640x336), creating a correct aspect ratio.

Is Mediacoder completely manual, or is it supposed to be auto-resizing to maintain correct aspect ration (see details of original files listed in top of this posting)...

ORIGINAL FILE PROPERTIES:
Codec/String : MPEG-2 Video BitRate/String : 9800 Kbps BitRate_Mode : CBR
Width : 720 Height : 480 AspectRatio/String : 16/9 FrameRate/String : 29.97 fps
Bits/(Pixel*Frame) : 0.946 Delay : 25257 PlayTime/String : 580h 31mn Standard : NTSC

Anyone out there who can advise?

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