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• How to convert to QString from const char* result from ffmpeg C function

  18 octobre 2022, par Lucas

  I use the ffmpeg library in c++ / qt project

  


  extern "C" {&#xA;    #include <libavformat></libavformat>avformat.h>&#xA;    #include <libavutil></libavutil>dict.h>&#xA;}&#xA;

  


  With this I read the media metadata from a local music file. This works quite fine :

  


  avformat_open_input(&format_song, path, NULL, NULL);

while((tag = av_dict_get(format_song->metadata, "", tag, AV_DICT_IGNORE_SUFFIX))){
                std::cout << tag.key << tag.value << std::endl;
                // tag.value is a const char* (but in C!?)
}


  


  Altough the encoding of the tag.value seems to be different for files (maybe saved different in the id3tags). Here are some examples of different title values for different files :

  


  "Töhne" [ö]
"Die Ärzte" [Ä]
"Für Immer"


  


  How to convert this to a readable QString ?

  


  There are some problems with the encoding of special characters. For most cases the following works :

  


  QString result = QString(tag->value).normalized(QString::NormalizationForm_C);
//or:
QString result = QString::fromUtf8(tag->value);


  


  But sometimes this results in a U+FFFD � REPLACEMENT CHARACTER for some "Ü" "Ä" "ß" etc. chars.
But in in that cases fromLocal8Bit works. So I end up testing for replacement characters and choose a different conversion :

  


  if(result.contains(QChar::ReplacementCharacter)){
      result = QString::fromLocal8Bit(tag->value);
}


  


  I expect there is a better way to do this ?

  


• x86/lpc : implement a new Welch windowing function

  19 septembre 2022, par Lynne

  x86/lpc : implement a new Welch windowing function
  Old one was written with the assumption only even inputs would be given.
  
  This very messy replacement supports even and odd inputs, and supports
  
  AVX2 for extra speed. The buffers given are usually quite big (4k samples),
  
  so the speedup is worth it.
  
  The new SSE version is still faster than the old inline asm version by 33%.
  Also checkasm is provided to make sure this monstrosity works.
  This fixes some FATE tests.
  

  • [DH] libavcodec/x86/Makefile
  • [DH] libavcodec/x86/lpc.asm
  • [DH] libavcodec/x86/lpc.c
  • [DH] libavcodec/x86/lpc_init.c
  • [DH] tests/checkasm/Makefile
  • [DH] tests/checkasm/checkasm.c
  • [DH] tests/checkasm/checkasm.h
  • [DH] tests/checkasm/lpc.c

• avcodec/vp8, vp9 : Avoid using VP56mv and VP56Frame in VP8/9

  23 juillet 2022, par Andreas Rheinhardt

  avcodec/vp8, vp9 : Avoid using VP56mv and VP56Frame in VP8/9
  Instead replace VP56mv by new and identical structures VP8mv and VP9mv.
  
  Also replace VP56Frame by VP8FrameType in vp8.h and use that
  
  in VP8 code. Also remove VP56_FRAME_GOLDEN2, as this has only
  
  been used by VP8, and use VP8_FRAME_ALTREF as replacement for
  
  its usage in VP8 as this is more in line with VP8 verbiage.
  This allows to remove all inclusions of vp56.h from everything
  
  that is not VP5/6. This also removes implicit inclusions
  
  of hpeldsp.h, h264chroma.h, vp3dsp.h and vp56dsp.h from all VP8/9
  
  files.
  (This also fixes a build issue : If one compiles with -O0 and disables
  
  everything except the VP8-VAAPI encoder, the file containing
  
  ff_vpx_norm_shift is not compiled, yet this is used implicitly
  
  by vp56_rac_gets_nn() which is defined in vp56.h ; it is unused
  
  by the VP8-VAAPI encoder and declared as av_unused, yet with -O0
  
  unused noninline functions are not optimized away, leading to
  
  linking failures. With this patch, said function is not included
  
  in vaapi_encode_vp8.c any more.)
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/nvdec_vp8.c
  • [DH] libavcodec/vaapi_vp8.c
  • [DH] libavcodec/vp56.h
  • [DH] libavcodec/vp8.c
  • [DH] libavcodec/vp8.h
  • [DH] libavcodec/vp9.c
  • [DH] libavcodec/vp9_mc_template.c
  • [DH] libavcodec/vp9block.c
  • [DH] libavcodec/vp9dec.h
  • [DH] libavcodec/vp9mvs.c
  • [DH] libavcodec/vp9prob.c
  • [DH] libavcodec/vp9recon.c
  • [DH] libavcodec/vp9shared.h