Recherche avancée

Sur d’autres sites (6512)

• avfilter/af_afade : improve accuracy and speed of gain computation

  25 novembre 2015, par Ganesh Ajjanagadde

  avfilter/af_afade : improve accuracy and speed of gain computation
  Gain computation for various curves was being done in a needlessly
  
  inaccurate fashion. Of course these are all subjective curves, but when
  
  a curve is advertised to the user, it should be matched as closely as
  
  possible within the limitations of libm. In particular, the constants
  
  kept here were pretty inaccurate for double precision.
  Speed improvements are mainly due to the avoidance of pow, the most
  
  notorious of the libm functions in terms of performance. To be fair, it
  
  is the GNU libm that is among the worst, but it is not really GNU libm’s fault
  
  since others simply yield a higher error as measured in ULP.
  "Magic" constants are also accordingly documented, since they take at
  
  least a minute of thought for a casual reader.
  Reviewed-by : Paul B Mahol <onemda@gmail.com>
  
  Signed-off-by : Ganesh Ajjanagadde <gajjanagadde@gmail.com>
  

  • [DH] libavfilter/af_afade.c

• Bash Script For FFMPEG

  24 octobre 2016, par armight29

  trying to write simple script to encode files but keep getting this error msg :

  /usr/bin/cm : line 28 : syntax error near unexpected token

  else'
/usr/bin/cm: line 28:

  else’

  and here is the script called cm :

  #!/bin/bash
  
  echo Filename?
  
  read Filename
  
  echo Enter Target Filesize In Megabytes..
  
  read TargetSize
  
  echo ffmpeg preset?
  
  read PRESET
  
  Duration='ffprobe -i $Filename -show_entries format=duration -v quiet -of csv="p=0"'
  
  Bitrate='($TargetSize*8192)/$Duration'
  
  exiftool -b $Filename -ImageSize
  
  echo WIDTH=?
  
  read WIDTH
  
  echo HEIGHT=?
  
  read HEIGHT
  
  echo Padding Required? Enter 'y' or 'n'
  
  read PADANSWR
  
  if [PADANSWR = 'y'] then
  
  echo X=?
  
  read X
  
  echo Y=?
  
  read Y
  
  ffprobe -show_entries stream=index,codec_type:stream_tags=language -of compact $Filename -v 0 | grep eng
  
  echo ENG AUDIO INDEX?
  
  read ENGAUDIOINDEX
  
  echo ENG SUBS INDEX?
  
  read ENGSUBSINDEX
  
  ffmpeg -i $Filename -strict -2 -c:v libx264 -preset $PRESET  -b:v $Bitrate -vf "padding=width=$WIDTH:height=$HEIGHT:x=$X:y=$Y:color=black" pass 1 -f matroska /dev/null -c:a ac3 -b:a 192k && ffmpeg -i $Filename -strict -2 -c:v libx264 -preset $PRESET  -b:v $Bitrate -vf "padding=width=$WIDTH:height=$HEIGHT:x=$X:y=$Y:color=black" -pass 1 -f matroska ENCODE1.mkv -c:a ac3 -b:a 192k
  
  else
  
      ffmpeg -i $Filename -strict -2 -c:v libx264 -preset $PRESET -b:v $Bitrate -threads 12 -pass 1 -f matroska /dev/null -c:a ac3 -b:a 192k && ffmpeg -i $Filename -strict -2 -c:v libx264 -preset $PRESET -b:v $Bitrate -threads 12 -pass 1 -f matroska ENCODE1.mkv -c:a ac3 -b:a 192k
  
  fi

  just started coding in bash—how long can the lines in a script be or do i need to use the ’\’ character—if i do use the ’\’ character does it need a space after it ? TIA

• Reading subtitle metadata from mpeg files using ffprobe

  26 septembre 2022, par Kaydee Dunlop

  I'm using ffmpeg or to be more specific ffprobe which is part of the ffmpeg toolstack to read subtitle information from a mpeg file. Anyway, I'm facing an issue I currently don't fully understand. If I use the following command :

  


  ffprobe -of json -show_streams -show_format


  


  I get back something like this :

  


      {
        "index": 6,
        "codec_name": "mov_text",
        "codec_long_name": "MOV text",
        "codec_type": "subtitle",
        "codec_tag_string": "tx3g",
        "codec_tag": "0x67337874",
        "width": 3840,
        "height": 240,
        "id": "0x6",
        "r_frame_rate": "0/0",
        "avg_frame_rate": "0/0",
        "time_base": "1/1000",
        "start_pts": 0,
        "start_time": "0.000000",
        "duration_ts": 6706616,
        "duration": "6706.616000",
        "bit_rate": "95",
        "nb_frames": "4028",
        "extradata_size": 48,
        "disposition": {
            "default": 0,
            "dub": 0,
            "original": 0,
            "comment": 0,
            "lyrics": 0,
            "karaoke": 0,
            "forced": 0,
            "hearing_impaired": 0,
            "visual_impaired": 0,
            "clean_effects": 0,
            "attached_pic": 0,
            "timed_thumbnails": 0,
            "captions": 0,
            "descriptions": 0,
            "metadata": 0,
            "dependent": 0,
            "still_image": 0
        },
        "tags": {
            "creation_time": "2022-09-11T01:02:33.000000Z",
            "language": "eng"
        }
    },


  


  you can see, I have several options that can be set for the disposition section, I'm especially interested in "forced" and "hearing_impaired". To set the value for these options I'm trying to use a tool called "Subler" which is a tool to metarise mpeg files and their containing tracks. But for some reason, ffprobe does not seem to match with the fields Subler sets... So I'm kind stuck as I'm never really able to find out if a subtitle track is forced, hearing_impaired (SDH) etc. Is there any kind of workaround for this problem, maybe an extra option I have to set with ffprobe or so ? Is there maybe an alternative tool that can ?

  


  If you are more interested into this issue I also uploaded a test scenario which has forced subtitles, normal subtitles and SDH subtitles properly set, it also contains screenshots and the raw SRT files, which are basically not needed as the subs are already embedded into the mp4 file, but just in case I also attached them.

  


  https://drive.google.com/file/d/1ZZ32i17A33Lhpn4a5BDg033yV9PbZhtS/view?usp=sharing