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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

• python 3 using ffmpeg in a subprocess getting stderr decoding error

  4 mai 2024, par jdauthre

  I am running ffmpeg as a subprocess and using the stderr to get various bits of data like the subtitles stream Id's. It works fine for most videos, but one with japanese subtitles results in an error :

  


  'charmap' codec can't decode byte in position xxx : character maps to

  


  Much googling suggests the problem is that the japanese requires unicode, whereas English does not. Solutions offered refer to problems with files, and I cannot find a way of doing the same with the stderr. Relevent Code is below :

  


  command = [ffmpeg,"-y","-i",fileSelected,"-acodec","pcm_s16le",
                  "-vn","-t","3", "-f",            "null","-"]
print(command)   
proc = subprocess.Popen(command,stderr=PIPE,Jstdin=subprocess.PIPE,
                            universal_newlines=True,startupinfo=startupinfo)
  
stream = ""    
for line in proc.stderr:
    try:
        print("line",line)
    except exception as error:
        print("print",error)
        line = line[:-1]
        if "Stream #" in line:
            estream = line.split("#",1)[1]
            estream =estream.split(" (",1)[0]
            print("estream",estream)
            stream = stream + estream +"\n"  #.split("(",1)[0] 
            stream = stream + estream +"\n"


  


• 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 ?