Sur d’autres sites (8568)

• Why this shell command doesn't work ? ('command' works but 'command|cat' doesn't work)

  16 octobre 2018, par yabee

  Problem

  The following code outputs like...

  $ ffprobe -show_frames -select_streams v test.mp4 2>/dev/null|grep -A 2 key_frame=1
  
  key_frame=1
  
  pkt_pts=0
  
  pkt_pts_time=0:00:00.000000
  
  --
  
  key_frame=1
  
  pkt_pts=41041
  
  pkt_pts_time=0:00:01.710042
  
  --
  
  key_frame=1
  
  pkt_pts=64064
  
  pkt_pts_time=0:00:02.669333
  
  --
  
  key_frame=1
  
  pkt_pts=87087
  
  pkt_pts_time=0:00:03.628625
  
  --
  
  ...

  But the folowing one outputs nothing.

  $ ffprobe -show_frames -select_streams v test.mp4 2>/dev/null|grep -A 2 key_frame=1|cat

  And...

  $ ffprobe -show_frames -select_streams v test.mp4 2>/dev/null|grep key_frame=1
  
  key_frame=1
  
  key_frame=1
  
  key_frame=1
  
  key_frame=1
  
  $ ffprobe -show_frames -select_streams v test.mp4 2>/dev/null|grep key_frame=1|cat
  
  # Nothing outputted.

  Why ?

  Expected result

  What actually I want to do is

  $ ffprobe -show_frames -select_streams v test.mp4 2>/dev/null|grep -A 2key_frame=1|grep time
  
  pkt_pts_time=0:00:00.000000
  
  pkt_pts_time=0:00:01.710042
  
  pkt_pts_time=0:00:02.669333
  
  pkt_pts_time=0:00:03.628625
  
  ...

  But its result is

  $ ffprobe -show_frames -select_streams v test.mp4 2>/dev/null|grep -A 2key_frame=1|grep time
  
  # Nothing outputted.

  Grep works correctory exept it’s after ffprobe.

  $ seq 30|grep 1|grep 2
  
  12
  
  21

  Environment

  • Bash on Ubuntu on Windows 10 Pro
    • Windows version : 1803
    • Windows OS build : 17134.345

  Environment of Ubuntu :

  $ cat /etc/lsb-release
  
  DISTRIB_ID=Ubuntu
  
  DISTRIB_RELEASE=18.04
  
  DISTRIB_CODENAME=bionic
  
  DISTRIB_DESCRIPTION="Ubuntu 18.04.1 LTS"
  
  
  
  $ bash --version
  
  GNU bash, version 4.4.19(1)-release (x86_64-pc-linux-gnu)
  
  Copyright (C) 2016 Free Software Foundation, Inc.
  
  License GPLv3+: GNU GPL version 3 or later /gnu.org/licenses/gpl.html>
  
  
  
  This is free software; you are free to change and redistribute it.
  
  There is NO WARRANTY, to the extent permitted by law.
  
  
  
  $ ffprobe
  
  ffprobe version 3.4.4-0ubuntu0.18.04.1 Copyright (c) 2007-2018 the FFmpeg developers
  
    built with gcc 7 (Ubuntu 7.3.0-16ubuntu3)
  
    configuration: --prefix=/usr --extra-version=0ubuntu0.18.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
  
    libavutil      55. 78.100 / 55. 78.100
  
    libavcodec     57.107.100 / 57.107.100
  
    libavformat    57. 83.100 / 57. 83.100
  
    libavdevice    57. 10.100 / 57. 10.100
  
    libavfilter     6.107.100 /  6.107.100
  
    libavresample   3.  7.  0 /  3.  7.  0
  
    libswscale      4.  8.100 /  4.  8.100
  
    libswresample   2.  9.100 /  2.  9.100
  
    libpostproc    54.  7.100 / 54.  7.100
  
  Simple multimedia streams analyzer
  
  usage: ffprobe [OPTIONS] [INPUT_FILE]
  
  
  
  You have to specify one input file.
  
  Use -h to get full help or, even better, run 'man ffprobe'.

  What is problem ?

  Does grep or ffprobe change its behavior by existence of pipe in this case ?
  Thanks.

• Piping cURL output to FFmpeg doesn't work with mp4 files

  8 novembre 2015, par Konstantin

  I would like to pipe cURL output to FFmpeg the following way in my Ruby script to strip off metadata, chapters and maybe set other metadata too in the future :

  #!/usr/bin/ruby
  
  url=ARGV[0]
  
  
  
  fname=url.split("/").last
  
  extension=File.extname(fname)
  
  options=""
  
  case extension 
  
    when /mp4/i
  
      format="mp4"
  
      options=" -movflags frag_keyframe+empty_moov "
  
    when /avi/i
  
      format="avi"
  
    when /mkv/i
  
      format="matroska"
  
    when /wmv/i
  
      format="asf"
  
    else
  
      format="matroska"
  
   end
  
  
  
  cmd=%Q{ curl -b cookie-file.txt #{url} -L -o - | ffmpeg -y -i - -map 0:v -map 0:a -c:v copy -c:a:0 copy -map_metadata -1 -map_chapters -1 #{options} -f #{format} - | cat > #{fname} }
  
  
  
  system cmd

  When the url (ARGV[0]) points to an .avi, .wmv or .mkv file the script do its job. However when it points to an .mp4 or .mov file it doesn’t work, because the input isn’t seekable and FFmpeg at first try to read the whole input. When url points to an mp4 file, output to stdout even doesn’t work, only when options " -movflags frag_keyframe+empty_moov " is used for the output format. Otherwise I got an error message : "muxer does not support non seekable output". Last cat command is needed because this command pipe will work in a CGI script, and will write its output to STDOUT with appropriate HTTP headers. What options should I use for the input pipe to make my script work with mp4 files too ?

• Drop the unofficial extension prefix for MPEG and MPEG-TS formats

  29 novembre 2014, par Florent Le Coz

  Drop the unofficial extension prefix for MPEG and MPEG-TS formats
  As per the RFCs :
  
  http://tools.ietf.org/html/rfc3555#page-38
  
  http://tools.ietf.org/html/rfc3003
  CC : libav-stable@libav.org
  

  • [DBH] libavformat/mp3enc.c
  • [DBH] libavformat/mpegtsenc.c
  • [DBH] libavformat/rawenc.c