[FFmpeg-user] Problem with vf pad ... help please

[Christian Ebert]

* Mark Himsley on Monday, September 17, 2012 at 07:40:43 +0100
> On 16/09/2012 23:35, Christian Ebert wrote:
>> * Mark Himsley on Sunday, September 16, 2012 at 14:20:12 +0100
>>> Input #0, avi, from '/home/toto/blender/dronez.avi':
>>> Duration: 00:03:11.24, start: 0.000000, bitrate: 1536 kb/s
>>>   Stream #0:0: Video: mpeg4 (DX50 / 0x30355844), yuv420p, 720x576
>>> 
>>> Your original video is a 4:3 standard definition 720x576 file. You
>>> might have a video player (QuickTime, for instance) that lies slightly
>>> and tells you the file is 768x576

That's not entirely true, at least as long as you do not
transcode with QT. Standard pal is exported e.g. from Final Cut
as is without fiddling of the display aspect ratio; or rather QT
does not recognize the DAR at all. Unless you tweak the "Scaled
Size" in the video properties settings it stays at 720x576. You
can then scale it to 788x576.

>>> because it knows that standard
>>> definition pixels are not square (although Apple should scale up to
>>> 788x576, but that's another argument).
>> 
>> I'm interested - man mplayer lists:
>> 
>> spal:    768x576 (square pixel PAL)
>> 
>> Does this reflect a common misconception?
>> 
>> On the other hand 788 is not divisible by 16 ...
>> 
>> If you don't mind elaborating.
> 
> Yes - it is a common misconception.
> 
> This BBC web page had lots of information, until the great web cull of
> early 2011, so here's a link to the way-back-machine:
> 
> http://replay.waybackmachine.org/20100826080627/www.bbc.co.uk/commissioning/tvbranding/picturesize.shtml
> 
> This Adobe web page describes how they got it wrong all the way up
> before After Effects CS4:
> 
> http://help.adobe.com/en_US/AfterEffects/9.0/WS3878526689cb91655866c1103906c6dea-7f3aa.html
> 
> This page also describes the difference between Adobe After Effects CS3
> and CS4:
> 
> http://www.mikeafford.com/blog/2009/03/pal-d1-dv-widescreen-square-pixel-settings-in-after-effects-cs4-vs-cs3/

Thanks for the pointers - now I know why I had this nagging
suspicion that something was not quite right DAR-wise with my
transcodings. For the web I will probably crop so I can stay with
"simple" aspect ratios, something like:

-vf crop=iw-18:ih,yadif,scale=640:480,setsar=1:1

-- 
\black\trash movie         _SAME  TIME  SAME  PLACE_
 --->> http://www.blacktrash.org/underdogma/stsp.php
\black\trash audio   _ANOTHER  TIME  ANOTHER  PLACE_
--->> http://www.blacktrash.org/underdogma/atap.html