[FFmpeg-trac] #7818(ffmpeg:new): crop filter can't do single pixel width

[FFmpeg]

#7818: crop filter can't do single pixel width
-------------------------------------+-------------------------------------
             Reporter:  adaerr       |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:  ffmpeg       |                  Version:  git-
                                     |  master
             Keywords:  crop filter  |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
 Summary of the bug:

 When trying to crop a rectangle that is one pixel wide (-vf crop=1:70),
 ffmpeg aborts without output with the error
 {{{
 [Parsed_crop_0 @ 0x55fc84e75600] Invalid too big or non positive size for
 width '0' or height '70'
 [Parsed_crop_0 @ 0x55fc84e75600] Failed to configure input pad on
 Parsed_crop_0
 }}}
 Expected was an output frame of width=1 by height=70 pixel from the input
 stream. Two pixels or more for the width work fine.

 How to reproduce:
 {{{
 % ffmpeg -i input -vf crop=1:70 -vframes 1 slice.png
 ffmpeg version 4.1.1-1 Copyright (c) 2000-2019 the FFmpeg developers
   built with gcc 8 (Debian 8.2.0-20)
 }}}
 [full log attached]

 This bug is also observed with a synthetic video source, e.g.
 {{{
 ffmpeg -f lavfi -i color -vf crop=1:70 -vframes 1 slice.png
 }}}

 Curiously, "crop=70:1" (i.e. single pixel ''height'') produces an error as
 well with the synthetic video, '''but''' works fine with the sample source
 I used (in other words, I am able to make single pixel ''high'' captures
 although not from the lavfi input).

 I reproduced the bug with an ffmpeg built from the current git master:
 {{{
 ffmpeg version N-93476-g391f884675 Copyright (c) 2000-2019 the FFmpeg
 developers
   built with gcc 8 (Debian 8.3.0-2)
 }}}

 Attached is the full log generated with the git build using the "-report"
 option. Here are some potentially relevant lines:
 {{{
 Command line:
 ./ffmpeg -report -f lavfi -i color -vf "crop=1:70" -vframes 1 slice.png
 ffmpeg version N-93476-g391f884675 Copyright (c) 2000-2019 the FFmpeg
 developers
 [...]
 Reading option '-vf' ... matched as option 'vf' (set video filters) with
 argument 'crop=1:70'.
 [...]
 [Parsed_color_0 @ 0x560e8f6ddf80] size:320x240 rate:25/1
 duration:-1.000000 sar:1/1
 [...]
 Stream mapping:
   Stream #0:0 -> #0:0 (rawvideo (native) -> png (native))
 [...]
 [Parsed_crop_0 @ 0x560e8f7259c0] Setting 'out_w' to value '1'
 [Parsed_crop_0 @ 0x560e8f7259c0] Setting 'out_h' to value '70'
 [graph 0 input from stream 0:0 @ 0x560e8f727a80] Setting 'video_size' to
 value '320x240'
 [...]
 [format @ 0x560e8f728280] auto-inserting filter 'auto_scaler_0' between
 the filter 'Parsed_crop_0' and the filter 'format'
 [AVFilterGraph @ 0x560e8f725b80] query_formats: 4 queried, 2 merged, 1
 already done, 0 delayed
 [auto_scaler_0 @ 0x560e8f72b400] picking rgb24 out of 10 ref:yuv420p
 alpha:0
 [Parsed_crop_0 @ 0x560e8f7259c0] w:320 h:240 sar:1/1 -> w:0 h:70 sar:1/1
 [Parsed_crop_0 @ 0x560e8f7259c0] Invalid too big or non positive size for
 width '0' or height '70'
 [Parsed_crop_0 @ 0x560e8f7259c0] Failed to configure input pad on
 Parsed_crop_0
 Error reinitializing filters!
 Failed to inject frame into filter network: Invalid argument
 Error while processing the decoded data for stream #0:0
 Conversion failed!
 }}}

--
Ticket URL: <https://trac.ffmpeg.org/ticket/7818>
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