Recherche avancée

Sur d’autres sites (4329)

• avcodec/vc1dec : Split VC-1 decoders from msmpeg4

  30 octobre 2022, par Andreas Rheinhardt

  avcodec/vc1dec : Split VC-1 decoders from msmpeg4
  The only msmpeg4 code that is ever executed by the VC-1 based
  
  decoders is ff_msmpeg4_decode_init() and what is directly
  
  reachable from it. This is :
  
  a) A call to av_image_check_size(), then ff_h263_decode_init(),
  
  b) followed by setting [yc]_dc_scale_table and initializing
  
  scantable/permutations.
  
  c) Afterwards, some static tables are initialized.
  
  d) Finally, slice_height is set.
  The replacement for ff_msmpeg4_decode_init() performs a)
  
  just like now ; it also sets [yc]_dc_scale_table,
  
  but it only initializes inter_scantable and intra_scantable
  
  and not permutated_intra_[hv]_scantable : The latter are only
  
  used inside decode_mb callbacks which are only called
  
  in ff_h263_decode_frame() which is unused for VC-1.*
  The static tables initialized in c) are not used at all by
  
  VC-1 (the ones that are used have been factored out in
  
  previous commits) ; this avoids touching 327KiB of .bss.
  slice_height is also not used by the VC-1 decoder (setting
  
  it in ff_msmpeg4_decode_init() is probably redundant after
  
  b34397b4cd780b5692548e7d021ec884c7217dba).
  * : It follows from this that the VC-1 decoder is not really
  
  based upon the H.263 decoder either ; changing this will
  
  be done in a future commit.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] configure
  • [DH] libavcodec/msmpeg4.c
  • [DH] libavcodec/msmpeg4dec.c
  • [DH] libavcodec/vc1dec.c

• 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