Le quintidi 25 messidor, an CCXXIII, Carl Eugen Hoyos a écrit : > I can confirm that there may be an issue > but it is not overlay-related: > $ ffmpeg -i input -vf > "split[x][z];[x]format=gray[x1];[x1]nullsink" > -strict -2 -vcodec jpeg2000 -ss 1 out1.avi > > $ ffmpeg -ss 1 -i input -vf > "split[x][z];[x]format=gray[x1];[x1]nullsink" > -strict -2 -vcodec jpeg2000 out2.avi
If the issue is that the output is converted to gray too, then this is the expected behaviour. Let me explain. I suspect users easily assume that "format=foo" means "convert to pixel format foo", but it does not; it really means "make sure the frames are in pixel format foo here". It usually involves converting at some point before, but not necessarily right before, and not necessarily a plain convert. The idea is that libavfilter tries to minimize the number of conversions. For example, assume the filter graph is "frobnicate,foobarify,format=foo", frobnicate supports many output formats including foo, and foobarify supports many formats provided it is the same at input and output (a lot of filters are like that). Then libavfilter will not convert at all, it will just select foo as the pixel format for all the frobnicate-foobarify-format branch. If there are no filter capable of outputting in pixel format foo, then libavfilter will have to convert, and it does so by inserting the scale filter somewhere. The exact place where it is inserted depends on the particulars of the filter graph. Usually, it does not matter. For the rare cases where it does matter, for example to be sure to deinterlace before converting, you need to insert the scale filter explicitly at the point you want the format conversion. In this particular case, my guess is that libavfilter decided to insert the scale filter before split. Insert explicitly after split and it should work as expected. I realize the documentation for the format filter is misleading. Regards, -- Nicolas George
signature.asc
Description: Digital signature
_______________________________________________ ffmpeg-user mailing list ffmpeg-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-user
