[MEncoder-users] cropdetect cuts off bottom of subtitles

Thijs Vermeir thijsvermeir at telenet.be
Sat Jan 21 22:51:16 CET 2006

On 21-jan-06, at 15:47, Raphael wrote:

> Raphael wrote:
>> RC wrote:
>>> On Fri, 20 Jan 2006 20:03:20 +0000
>>> Raphael <mencoder at lesshaste.plus.com> wrote:
>>>> The part that I chopped out (120 seconds from the beginning) is the
>>>> same  part as I am testing. So shouldn't cropdetect work on that  
>>>> 120
>>>> seconds  at least?
>>> No.  Any number of things can fool cropdetect.  Logos and all-black
>>> scense tend to do a good job of that.
>> That is very odd. I understand that if you cropdetect one part and  
>> then encode another it can obviously get it wrong. But if you  
>> cropdetect the same part you are encoding, and the source is a dvd  
>> (so no random noise) then surely it should just scan from the  
>> bottom and top (and left and right) until it hits something non- 
>> black.  You should then get the minimum and maximum in the  
>> appropriate directions rounded so that you don't chop any of the  
>> film out.
> It occurs to me (after talking on IRC) that maybe cropdetect  
> doesn't actually store the maximum lit area it ever finds. If this  
> is the case, then it is a problem. In my case the subtitles are  
> encoded into the film and so you never get the right settings from  
> cropdetect if it recalculates per scene without storing the maximum  
> (some subtitles have no "p"s and "g"s for example).  Is this what  
> it is doing?
yes, (I think)
I check only cropdetect on the scene with the most subs. Then I know  
for sure I got all subs and as few as black possible.


> Raphael
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