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

[Christian Ebert]

* Mark Himsley on Monday, September 17, 2012 at 14:50:31 +0100
> On 17/09/12 08:44, Christian Ebert wrote:
>> -vf crop=iw-18:ih,yadif,scale=640:480,setsar=1:1
> 
> Does crop default to centred (I honestly cannot remember)?

Yes. The crop filter takes additional parameters for x and y to
position the cropped area, but defaults to centered; see the
manual.

> Otherwise you'll crop all 18 pixels off one edge.

heh

> And, if your video has sub-sampled chroma (422 or 420 for example)

Not sure. I assume so:
http://en.wikipedia.org/wiki/Chroma_subsampling#4:2:0

Feel free to correct my ignorance.

> then you can only crop to even numbers, and you end up cropping 8
> pixels off one side and 10 pixels off the other.

If that's the case I'll have to live with that (for web
conversions to a straight 4/3 aspect ratio).

> But, yes, that's the idea.

OK

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