[FFmpeg-trac] #1520(undetermined:new): allow mathematical expressions for -t and -ss

[FFmpeg]

#1520: allow mathematical expressions for -t and -ss
-------------------------------------+-------------------------------------
             Reporter:  dericed      |                     Type:
               Status:  new          |  enhancement
            Component:               |                 Priority:  normal
  undetermined                       |                  Version:
             Keywords:               |  unspecified
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  0
-------------------------------------+-------------------------------------
 Summary of the bug:

 It seems that -t and -ss support integer and decimals up to the six places
 after the decimal (-t 1.033366 works but -t 1.0333666 doesn't). Sometimes
 greater precision is needed. Is it possible to support mathematical
 expression with -t and -ss as it is with some of the timing in the
 filters.

 For instance if I try to create a wav file that contains one NTSC frame's
 worth of silence, it will produce an error. The closest I can seem to get
 is with '-t 1.033367'.

 How to reproduce:
 {{{
 ffmpeg -t '1/(30000/1001)' -f lavfi -i aevalsrc=0 -c:a pcm_s16le out.wav
 ffmpeg version 0.11.1.git Copyright (c) 2000-2012 the FFmpeg developers
   built on Jul  5 2012 11:22:03 with gcc 4.2.1 (Apple Inc. build 5666)
 (dot 3)
   configuration: --prefix=/usr/local/Cellar/ffmpeg/HEAD --enable-shared
 --enable-gpl --enable-version3 --enable-nonfree --enable-hardcoded-tables
 --enable-libfreetype --cc=/usr/bin/gcc-4.2 --enable-libx264 --enable-
 libfaac --enable-libmp3lame --enable-librtmp --enable-libtheora --enable-
 libvorbis --enable-libvpx --enable-libxvid --enable-libopencore-amrnb
 --enable-libopencore-amrwb --enable-libass --enable-libvo-aacenc
   libavutil      51. 64.100 / 51. 64.100
   libavcodec     54. 33.100 / 54. 33.100
   libavformat    54. 15.100 / 54. 15.100
   libavdevice    54.  1.100 / 54.  1.100
   libavfilter     3.  0.101 /  3.  0.101
   libswscale      2.  1.100 /  2.  1.100
   libswresample   0. 15.100 /  0. 15.100
   libpostproc    52.  0.100 / 52.  0.100
 Invalid duration specification for t: 1/(30000/1001)
 }}}

-- 
Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1520>
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