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• Error writing to file when saving matplotlib animation with a given codec

  31 mars 2017, par idesh

  I’ve had trouble saving an mp4 animation created with matplotlib with a given codec. However I should mention beforehand that I could save the mp4 animation without specifying codecs and that seems to work fine, except that I am not able to insert this mp4 animation into powerpoint for a presentation. Powerpoint says it cannot read the file because it is missing 64bit codec.

  When digging further I discovered that Windows media player which is used by power point for the animations, has already some video codecs installed.

  So I thought of saving the initial matplotlib animation with one of these codecs, which is also compatible with ffmpeg. The command ffmpeg -codecs on terminal lists the supported codecs and I could spot the codecs common with ffmpeg and windows media player, ex : MSS1, MSS2

  So I tried to save the animation with the argument codec set as follows.

  anim = animation.FuncAnimation(fig, animate, 158,interval=300, blit=True)
  
  writer = animation.writers['ffmpeg']
  
  anim.save('film_v5.mp4', codec='mss1')

  Nevertheless it leads to an error, no matter what type of codec argument I put.

  So I was wondering perhaps there was someone savvy, willing to help me troubleshoot this problem. Despite my attempts I could not find any solution in the stackoverflow forum.

  Thank you in advance for your attention.

• lavu/tx : improve 3-point fixed precision

  14 février 2020, par Lynne

  lavu/tx : improve 3-point fixed precision
  There's just no reason not to when its so easy (albeit messy) and its also
  
  reducing the precision of all non-power-of-two transforms that use it.
  

  • [DH] libavutil/tx_priv.h
  • [DH] libavutil/tx_template.c

• fate : Fix the sub-mcc tests on Windows in eastern time zones

  11 août, par Martin Storsjö

  fate : Fix the sub-mcc tests on Windows in eastern time zones
  Previously, these tests failed when running on Windows, if the
  
  system is configured with a time zone east of Greenwich, i.e.
  
  with a positive GMT offset.
  The muxer converts the creation_date given by the user using
  
  av_parse_time to unix time, as a time_t. The creation_date is
  
  interpreted as a local time, i.e. according to the current time
  
  zone. (This time_t value is then converted back to a broken out
  
  local time form with localtime_r.)
  The given reference date/time, "1970-01-01T00:00:00", is the
  
  origin point for unix time, corresponding to time_t zero. However
  
  when interpreted as local time, this doesn't map to exactly zero.
  
  Time zones east of Greenwich reached this time a number of hours
  
  before the point of zero time_t - so the corresponding time_t
  
  value essentially is minus the GMT offset, in seconds.
  Windows mktime returns an error, returning (time_t)-1, when given
  
  such a "struct tm", while e.g. glibc mktime happily returns a
  
  negative time_t. av_parse_time doesn't check the return value of
  
  mktime for potential errors.
  This is observable with the following test snippet :
      struct tm tm =  0  ;
  
      tm.tm_year = 70 ;
  
      tm.tm_isdst = -1 ;
  
      tm.tm_mday = 1 ;
  
      tm.tm_hour = 0 ;
  
      time_t t = mktime(&tm) ;
  
      printf("%d-%02d-%02d %02d :%02d :%02d\n", tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday, tm.tm_hour, tm.tm_min, tm.tm_sec) ;
  
      printf("t %d\n", (int)t) ;
  By varying the value of tm_hour and the system time zone, one
  
  can observe that Windows mktime returns -1 for all time_t values
  
  that would have been negative.
  This range limit is also documented by Microsoft in detail at
  
  https://learn.microsoft.com/en-us/cpp/c-runtime-library/reference/mktime-mktime32-mktime64.
  To avoid the issue, pick a different, arbitrary reference time,
  
  which should have a nonnegative time_t for all time zones.
  

  • [DH] tests/fate/subtitles.mak
  • [DH] tests/ref/fate/sub-mcc-remux
  • [DH] tests/ref/fate/sub-mcc-remux-eia608
  • [DH] tests/ref/fate/sub-mcc-remux-eia608-bsf
  • [DH] tests/ref/fate/sub-mcc-remux-eia608-recode