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• avcodec/movtextdec : Sanitize style entries

  7 décembre 2021, par Andreas Rheinhardt

  avcodec/movtextdec : Sanitize style entries
  There are three types of style entries which are redundant :
  
  a) Entries with length zero. They are already discarded.
  
  b) Entries that are equivalent to the default style :
  
  They can be safely discarded.
  
  c) Entries that are equivalent to the immediately preceding style
  
  if the start of the current style coincides with the end of the
  
  preceding style. In this case the styles can be merged.
  This commit implements discarding/merging in cases b) and c).
  
  This fixes ticket #9548. In said ticket each packet contained
  
  exactly one style entry that covered the complete packet with
  
  the exception of the last character (probably created by a tool
  
  that didn't know that the style's end is exclusive). Said style
  
  coincided with the default style, leading to a superfluous reset,
  
  which is now gone.
  Reviewed-by : Philip Langdale <philipl@overt.org>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/movtextdec.c

• fftools/ffmpeg_filter : Avoid inserting hflip filter

  18 décembre 2021, par Andreas Rheinhardt

  fftools/ffmpeg_filter : Avoid inserting hflip filter
  The transpose filter has modes equivalent to "rotation by 90°/270°"
  
  followed by horizontal flips.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] fftools/ffmpeg_filter.c

• lavu/tx : add an RDFT implementation

  21 janvier 2022, par Lynne

  lavu/tx : add an RDFT implementation
  RDFTs are full of conventions that vary between implementations.
  
  What I've gone for here is what's most common between
  
  both fftw, avcodec's rdft and what we use, the equivalent of
  
  which is DFT_R2C for forward and IDFT_C2R for inverse. The
  
  other 2 conventions (IDFT_R2C and DFT_C2R) were not used at
  
  all in our code, and their names are also not appropriate.
  
  If there's a use for either, we can easily add a flag which
  
  would just flip the sign on one exptab.
  For some unknown reason, possibly to allow reusing FFT's exp tables,
  
  av_rdft's C2R output is 0.5x lower than what it should be to ensure
  
  a proper back-and-forth conversion.
  
  This code outputs its real samples at the correct level, which
  
  matches FFTW's level, and allows the user to change the level
  
  and insert arbitrary multiplies for free by setting the scale option.
  

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