[FFmpeg-devel] [RFC] scale filter can create output which scale filter cannot accept on its input

[Mark Himsley]

I know this is a bit of a bizarre filter chain, It's constructed to 
demonstrate the point I'm hoping to make, without using any of my code.

Clock10.mov is just a PAL DV, but I think any _interlaced_ file will do.

./ffmpeg -loglevel debug -i ~/Movies/Clock10.mov -vf 
"slicify=32,scale=0:0:interl=1,format=yuv420p,scale=0:0:interl=1,format=yuv422p,scale=0:0:interl=1,format=yuv420p" 
-pix_fmt yuv420p -vframes 1 -an -f rawvideo -y /dev/null

Essentially, the 'y' parameter in the slices of the output of the second 
scale is not aligned by 4 (the first slice is, in fact, 26 lines high, 
so the second slice starts at 26) so it is not valid for the input of 
the third scale.

I don't think the output of this filter chain should throw an assert.

I stumbled upon this when trying to make the fieldorder filter do slices.

Sorry to have not included my suggestion for a patch! My brain is fried.

Thanks

-- 
Mark