[FFmpeg-trac] #404(undetermined:new): Rounding error in scaling expression

[FFmpeg]

#404: Rounding error in scaling expression
----------------------------------------+---------------------------
Reporter:  blaw                         |       Owner:
    Type:  defect                       |      Status:  new
Priority:  normal                       |   Component:  undetermined
 Version:  git                          |  Resolution:
Keywords:  rouding scalling expression  |  Blocked By:
Blocking:                               |  Reproduced:  0
Analyzed:  0                            |
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Comment (by saste):

 Unreproducible here with the command (you need git of the day for testing
 it):
 {{{
 $ ffplay -f lavfi  "testsrc=s=352x480:sar=20/11,scale=iw:ow/dar"
 ffplay version N-32028-g34c9975, Copyright (c) 2003-2011 the FFmpeg
 developers
   built on Aug 21 2011 15:27:17 with gcc 4.4.5
   configuration: --prefix=/home/stefano --enable-libx264 --enable-libxvid
 --enable-librtmp --disable-shared --enable-static --enable-debug=3
 --enable-pthreads --enable-libvorbis --enable-avfilter --enable-gpl
 --enable-nonfree --enable-libmp3lame --enable-libtheora --enable-gpl
 --enable-x11grab --enable-libschroedinger --enable-libopenjpeg --enable-
 frei0r --enable-libopencv --disable-optimizations --disable-mmx --enable-
 libfreetype
   libavutil    51. 13. 0 / 51. 13. 0
   libavcodec   53. 11. 0 / 53. 11. 0
   libavformat  53.  9. 0 / 53.  9. 0
   libavdevice  53.  3. 0 / 53.  3. 0
   libavfilter   2. 34. 1 /  2. 34. 0
   libswscale    2.  0. 0 /  2.  0. 0
   libpostproc  51.  2. 0 / 51.  2. 0
 [testsrc @ 0xa2c0790] size:352x480 rate:25/1 duration:-1.000000 sar:20/11
 [scale @ 0xa28efe0] w:352 h:480 fmt:rgb24 -> w:352 h:264 fmt:yuv420p
 flags:0x2
 [lavfi @ 0xa2bf8a0] Estimating duration from bitrate, this may be
 inaccurate
 Input #0, lavfi, from 'testsrc=s=352x480:sar=20/11,scale=iw:ow/dar':
   Duration: N/A, start: 0.000000, bitrate: N/A
     Stream #0.0: Video: rawvideo, yuv420p, 352x264 [SAR 20:11 DAR 80:33],
 25 tbr, 25 tbn, 25 tbc
    5.32 A-V:  0.000 s:0.0 aq=    0KB vq=  817KB sq=    0B f=0/0   0/0
 }}}

 Please try and report, I guess it may be a platform-specific problem.
 Even in this case, you can force the h value to be a multiple of the
 chroma vertical subsampling value, for example by setting
 scale=iw:floor(ow/dar/hsub)*hsub.

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/404#comment:1>
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