[FFmpeg-devel] libavfilter scale problem

slippyr4 slippyr4
Thu Feb 18 15:54:13 CET 2010

Hi All,

I'm having an issue with libavfilter, in particular the scale filter, when
used in a chain with other filters.

I have built the latest ffmpeg+libavfilter as of today (libavfilter r5620,
which uses ffmpeg r21854 and libswscale r30520), and built ffmpeg with
--enable-memalign-hack --enable-shared --disable-static --enable-gpl
--enable-avfilter --enable-libmp3lame

Firstly, I have created a 1920x1080 resolution test source with the
ffmpeg -r 5 -s hd1080 -i %03d.jpg 1920x1080.mp4

I want to create a chain of filters which will have the effect of rotating
anticlockwise by 90 degrees and then scaling so that the video is sized

*ffmpeg -i 1920x1080.mp4 -vfilters "transpose,scale=810:1920"
produces an output in which the top half of the frame is correct, but the
bottom half is solid green.

However, if i do the equivalent transformation in two stages:-
*ffmpeg -i 1920x1080.mp4 -vfilters "transpose" transpose.mp4
ffmpeg -i  transpose.mp4 -vfilters "scale=810x1920" transpose_then_scale.mp4
*then the output is correct.

Is there some intricacy of the scale filter that i've not taken account of,
or is this a bug?

I can sent my example files to the list if that is of benefit. They are a
536KB zip file.

Any help is much appreciated.



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