Recherche avancée

Sur d’autres sites (6536)

• How to detect audio sampling rate with avprobe / ffprobe ?

  8 août 2013, par Devy

  I am using libav 9.6, installed via Homebrew.

  $ avprobe -version
  
  avprobe version 9.6, Copyright (c) 2007-2013 the Libav developers
  
    built on Jun  8 2013 02:44:19 with Apple LLVM version 4.2 (clang-425.0.24) (based on LLVM 3.2svn)
  
  avprobe 9.6
  
  libavutil     52.  3. 0 / 52.  3. 0
  
  libavcodec    54. 35. 0 / 54. 35. 0
  
  libavformat   54. 20. 3 / 54. 20. 3
  
  libavdevice   53.  2. 0 / 53.  2. 0
  
  libavfilter    3.  3. 0 /  3.  3. 0
  
  libavresample  1.  0. 1 /  1.  0. 1
  
  libswscale     2.  1. 1 /  2.  1. 1

  Even though the sampling rate is displayed in the stdout in the command line output, the -show_format option doesn't surface the sampling rate information for the audio file at all.

  Here is the BASH terminal output :

  $ avprobe  -v verbose -show_format -of json  sample.gsm
  
  avprobe version 9.6, Copyright (c) 2007-2013 the Libav developers
  
    built on Jun  8 2013 02:44:19 with Apple LLVM version 4.2 (clang-425.0.24)
  
  (based on LLVM 3.2svn)
  
    configuration: --prefix=/usr/local/Cellar/libav/9.6 --enable-shared
  
  --enable-pthreads --enable-gpl --enable-version3 --enable-nonfree
  
  --enable-hardcoded-tables --enable-avresample --enable-vda --enable-gnutls
  
  --enable-runtime-cpudetect --disable-indev=jack --cc=cc --host-cflags=
  
  --host-ldflags= --enable-libx264 --enable-libfaac --enable-libmp3lame
  
  --enable-libxvid --enable-avplay
  
    libavutil     52.  3. 0 / 52.  3. 0
  
    libavcodec    54. 35. 0 / 54. 35. 0
  
    libavformat   54. 20. 3 / 54. 20. 3
  
    libavdevice   53.  2. 0 / 53.  2. 0
  
    libavfilter    3.  3. 0 /  3.  3. 0
  
    libavresample  1.  0. 1 /  1.  0. 1
  
    libswscale     2.  1. 1 /  2.  1. 1
  
  [gsm @ 0x7f8012806600] Estimating duration from bitrate, this may be inaccurate
  
  Input #0, gsm, from 'sample.gsm':
  
    Duration: 00:03:52.32, start: 0.000000, bitrate: 13 kb/s
  
      Stream #0.0: Audio: gsm, 8000 Hz, mono, s16, 13 kb/s
  
  {  "format" : {
  
      "filename" : "sample.gsm",
  
      "nb_streams" : 1,
  
      "format_name" : "gsm",
  
      "format_long_name" : "raw GSM",
  
      "start_time" : "0.000000",
  
      "duration" : "232.320000",
  
      "size" : "383328.000000",
  
      "bit_rate" : "13200.000000"
  
    }}

  And the python code example :

  >>> filename = 'sample.gsm'
  
  >>> result = subprocess.check_output(['avprobe', '-show_format', '-of',
  
  'json', filename])
  
  avprobe version 9.6, Copyright (c) 2007-2013 the Libav developers
  
    built on Jun  8 2013 02:44:19 with Apple LLVM version 4.2
  
  (clang-425.0.24) (based on LLVM 3.2svn)
  
  [gsm @ 0x7fe0b1806600] Estimating duration from bitrate, this may be
  
  inaccurate
  
  Input #0, gsm, from 'sample.gsm':
  
    Duration: 00:03:52.32, start: 0.000000, bitrate: 13 kb/s
  
      Stream #0.0: Audio: gsm, 8000 Hz, mono, s16, 13 kb/s
  
  >>> print result
  
  {  "format" : {
  
      "filename" : "sample.gsm",
  
      "nb_streams" : 1,
  
      "format_name" : "gsm",
  
      "format_long_name" : "raw GSM",
  
      "start_time" : "0.000000",
  
      "duration" : "232.320000",
  
      "size" : "383328.000000",
  
      "bit_rate" : "13200.000000"
  
  }}

  So I am aware that sampling rate could be a stream specific display to be shown in -show_format option results. But there isn't any other options to detect the sampling rate on a specific audio stream even though it's possible to set it with -ar when re-encoding it.

  I filed a ticket to libav but I am just curious if there is any other way to extract sampling rate from libav probing utils. I appreciate the answer beforehand.

  PS : it would be the same question for the upstream project of ffmpeg (ffprobe) in this case.

• ImgFlip Gif Generator

  30 juillet 2013, par user1960364

  Reference : http://imgflip.com/gifgenerator

  So, I don't need the web UI and all the cusomizations. But I've been trying to figure out how to slice and convert a mp4 or mov to an animated gif automagically. I've looked at several ways of doing it with imagemagick/ffmpeg but none of them rendered results as good as imgflip. I always end up with some 24bit color-looking gif instead or some impractically large file.

  Any suggestions/ideas on how to do it as efficiently as imgflip ?

  Thanks :)

  — Edit —
  I found this on reddit :

  #!/bin/bash
  
  
  
  # Extracts each frame of the video as a single gif
  
  ffmpeg -i $1 out%04d.gif
  
  
  
  # Combines all the frames into one very nicely animated gif.
  
  convert -delay 4 out*.gif anim.gif
  
  
  
  # Optimizes the gif using imagemagick
  
  convert -layers Optimize anim.gif optimized_output.gif
  
  
  
  # Cleans up the leftovers
  
  rm out*
  
  rm anim.gif 

  Using that, I created (and yes, I'm on windows) :

  ffmpeg -i v.mp4 -r 10 -q:v 1 tmp/out%04d.jpg
  
  convert -delay 10 tmp/out*.jpg jpg-d10.gif
  
  echo y | del tmp

  And got decent quality, even this creates an 8MB file for a small 6sec 480x480 clip at 10fps. And because it's a video and not vector or series of images with very few colors, extracting jpg images does better compression than -layers Optimize. However, for some reason, -qscale/-q:v on the frame extraction does not effect the final file size, just the quality.

• FFProbe Duration Integer Expression Expected ?

  25 décembre 2017, par kpjVideo

  I’m trying compare the number of seconds in a video provided by ffprobe.

  In my bash script I have the following :

  duration=`ffprobe -i $fileread.mp4 -show_format -v quiet | sed -n 's/duration=//p'` < /dev/null

  This returns a double > 8248.021633

  I want to compare this number to an integer like so :

  if [ "$duration" -lt 300 ]; then
  
     # do stuff
  
  fi

  Everytime the script runs I get :

  line 15: [: 8248.021633: integer expression expected

  Is this because the output is simply not an integer ? I have also tried making a new variable with var=$(($duration)) with no luck.

  Any help much appreciated, Thanks.