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Old 15th February 2009, 19:14   #1  |  Link
OffColour
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Fix Aspect Ratio?

Hi folks,

I'm really confused.
I have some home videos at 704x586 and they're anamorphic. When I play them in WMP it all looks fine and 16:9 as it should be. When I play in VLC it comes out like 2.35:1, i.e very stretched.

According to MediaInfo it has an aspect ratio of 2:35:1, but if I demux, open in Restream and resave with a 16:9 flag it still says the new video is 2.35.
Opening the same videos in the old tool DVD Patcher reports them at 16:9.

Any idea what's going on and how I can get the flag set correctly at 16:9 (taking VLC as the arbiter of the file being right)?

Thanks

Gary
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Old 15th February 2009, 21:23   #2  |  Link
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Which container do you have them saved in? AVI, MP4 or MKV?
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Old 15th February 2009, 22:11   #3  |  Link
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Just a standard MPEG2 program stream, i.e. a .MPG file.
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Old 17th February 2009, 00:40   #4  |  Link
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Not positive, but I think this is related to the sequence_display_extension.
Flicking around the web there seems to be a lot of software that is using this information incorrectly.

See http://www.mail-archive.com/ffmpeg-i.../msg02442.html and http://social.technet.microsoft.com/...-c4f2de5e99de/

I think VLC has also fallen into this trap. The odd thing is that WMP seems to actually get it right...

Thoughts?

BTW, Also found this on a commercial DVD, but strangely, playing the DVD in VLC is fine. Playing a VOB ripped from the DVD has the dodgy aspect ratio.

Ah well, looks like it's a player implementation problem rather than anything wrong with the files.

Last edited by OffColour; 17th February 2009 at 00:57.
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Old 17th February 2009, 02:19   #5  |  Link
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@OffColour

Hi!

Although I have no answer for your problem, you've piqued my curiosity and I have a question:

With what video equipment did you shoot "some home videos at 704x586 and they're anamorphic." that "According to MediaInfo it has an aspect ratio of 2:35:1"?
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Old 18th February 2009, 00:54   #6  |  Link
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It's a Panasonic SD-S7
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Old 18th February 2009, 10:02   #7  |  Link
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Quote:
Originally Posted by OffColour View Post
It's a Panasonic SD-S7
Here's what the manual says about your camcorders capturing capabilities: -

Quote:
Motion pictures
Recording media
SD Memory Card: 256 MB/512 MB/1 GB/2 GB (FAT12 and FAT16 format corresponding)
SDHC Memory Card: 4 GB/8 GB/16 GB (FAT32 format corresponding)
Picture size: 704 x 576
Compression: MPEG2 (SD-Video standard compliant)
Recording mode and transfer rate
XP: 10 Mbps (VBR), SP: 5 Mbps (VBR),
LP: 2.5 Mbps (VBR)
Audio compression: MPEG1-Layer2 compliant (stereo)
There's also an option to capture moving images in either 16:9 or 4:3....

It all seems very straight forward, so I too am interested why you're having problems

Are you able to upload a short 4:3 and 16:9 sample?
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Old 18th February 2009, 21:52   #8  |  Link
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I'll grab a short clip and upload it later.

As another interesting tidbit, I looked at the DAR in the file: it's 0x33, i.e. 16:9 at 25fps. This is why I think the sizes in the sequence_display_extension are causing the problem. This is exactly the same in the VOB from the commercial DVD.
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Old 19th February 2009, 00:29   #9  |  Link
OffColour
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Cracked it

This does seem to to go back to my original comment with the link to the ffmpeg article.

Some players use s_d_e and some don't. Some mpeg2's include s_d_e and some don't.

My understanding is that using it is optional, i.e. it holds information that could be used for 4:3 pan & scan.

VLC (ffmpeg) seems to uses the information in s_d_e by default. Running my videos through the latest version of SDCopy changes both the DAR to 16:9 and the sizes in the s_d_e so that it'll be shown as 16:9 whether or not sde is used or not. Previous versions just changed the DAR which is fine for WMP as it doesn't use the sde info. See this post: http://camcorderinfo.com/bbs/showpos...6&postcount=62

So, I have no idea what the correct default behaviour for a media player should be (personally I'd say ignore sde and just use DAR with an option to turn on the sde), but there seem to be inconsistencies out there. I also don't know if the use of sde as done in ffmpeg is correct or not, but based upon the earlier link it seems that at least one other person thinks it's wrong.

If anyone is interested in a clip with 16:9 DAR that plays at 2.35:1 then it's here:
http://rapidshare.com/files/19976765...Ratio.MPG.html

This has been an interesting learning exercise...

Gary
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