#11438: vf_crop filter breaks setting variables like x=x+1
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Reporter: Alan Amaral | Type: defect
Status: new | Priority: normal
Component: avfilter | Version: 6.1.1
Keywords: vf_crop | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Summary of the bug:
If you create a filter graph with a crop filter, and zmq enabled, you
can't set any of the values, x, y as recursive expressions, like x=x+1.
In the overlay filter you can set x=x+1 and for each frame the value of x
is increased by 1, and automatically pans the video, for example. This
does not work with the crop filter. Setting x=10 works, as does setting
x=10+10 but setting x=x+10 doesn't work and breaks things. In fact, as
far as I can tell setting x or y to any expression involving x or y, like
x=x or y=y, which should leave the positions unchanged, doesn't give the
expected results. Setting x=x or y=y seems to set the x,y position to the
center of the input area. This looks intentional given this code from
vf_crop.c:
{"x", "set the x crop area expression", OFFSET(x_expr),
AV_OPT_TYPE_STRING, {.str = "(in_w-out_w)/2"}, 0, 0, TFLAGS },
{"y", "set the y crop area expression", OFFSET(y_expr),
AV_OPT_TYPE_STRING, {.str = "(in_h-out_h)/2"}, 0, 0, TFLAGS },
but seems to make absolutely no sense, given that other filters (such as
vf_overlay) allow recursive variable expressions, like x=x+1, which cause
the x value to increase by 1 for each frame, and x=x causes the motion to
stop.
How to reproduce:
Build an ffmpeg command with a crop filter and try to control the x and y
position using zmqsend.
Patches should be submitted to the ffmpeg-devel mailing list and not this
bug tracker.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/11438>
FFmpeg <https://ffmpeg.org>
FFmpeg issue tracker
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