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• Library for decoding H.264 RTSP stream

  28 juillet 2015, par Saurabh Gandhi

  I was planning to decode H.264 based RTSP stream using FFMPEG in OpenCV but, when I tried so it gave some errors. Later, I found that many people have faced issues while decoding H.264 stream using ffmpeg (libavcodec). Typically the below mentioned error messages pop-up while using libavcodec :

  "[h264 @ 0xa766dd0]concealing 1200 DC, 1200 AC, 1200 MV errors"

  Has anyone used any other library successfully for decoding H.264 based RTSP. If so, which is the library (I have heard of live555 which is used within vlc player for decoding such streams). I would also like to know the output format and how it can be made compatible with OpenCV (typically within opencv we can use cvQueryFrame to directly extract a frame from a video stream, but in case we are using a library other than ffmpeg how to go about it).

  Thanks in advance.

  Regards,

  Saurabh Gandhi

• FFMPEG - How to Extract Frames As Images While Removing Sequentially Duplicate Frames

  19 mars 2017, par Michael Nelson

  Is there any way (via script or preferably some parameter in calling ffmpeg that I missed) to extract frames from an avi file and ignore sequentially duplicate frames, thus being able to go through the pictures looking only at the deltas/changes ?

  I frequently have to record meetings at work and a lot of the time, the client screen that I am looking at is not changing while we are talking over the phone. After the meeting is over, I need to use these images as part of our documentation and specifications gathering.

  I know that I could just output every frame and run them through any given duplicate file remover utility, but this would remove ALL duplicate frames. So, if the frames extracted went like this :

  A, A, A, B, B, B, B, C, C, A, A, C, C, C, B, B, B ...

  Running them through a typical duplicate file remover, I would get : A, B, C

  What I would want is : A, B, C, A, C, B

  The command that I am currently using to extract the images is :

  ffmpeg.exe -i file.avi -ss 0 -sameq -f image2 -r 1 images%5d.png

  I was getting every frame beforehand (removing the -r 1 from above), but that was generating way too many frames to deal with since these online meetings can go for hours, so for now, I get one frame per second from the file.

  A Windows based solution would be preferable, however, I’m sure other people would be interested in solutions on other platforms if available.

  Any solution or point in the right direction is much appreciated.

• ffmpeg : using the returned data in php

  4 décembre 2013, par user1503606

  I have started using ffmpeg and I am very new to it, so please bear with me.

  I have installed ffmpeg on my server and it works great ; I can run certain commands and get output data when logged in via ssh

  For example I can run

  ffmpeg -i Sleep\ Away.mp3 

  Which returns the following :

  ffmpeg version 0.8.5, Copyright (c) 2000-2011 the FFmpeg developers
  
    built on Aug 20 2012 09:28:43 with clang 3.1 (tags/Apple/clang-318.0.61)
  
    configuration: --enable-nonfree --enable-gpl --enable-version3 --enable-postproc --enable-swscale --enable-avfilter --enable-libmp3lame --enable-libvorbis --enable-libtheora --enable-libfaac --enable-libxvid --enable-libx264 --enable-libvpx --enable-hardcoded-tables --enable-shared --enable-pthreads --disable-indevs --cc=clang
  
    libavutil    51.  9. 1 / 51.  9. 1
  
    libavcodec   53.  7. 0 / 53.  7. 0
  
    libavformat  53.  4. 0 / 53.  4. 0
  
    libavdevice  53.  1. 1 / 53.  1. 1
  
    libavfilter   2. 23. 0 /  2. 23. 0
  
    libswscale    2.  0. 0 /  2.  0. 0
  
    libpostproc  51.  2. 0 / 51.  2. 0
  
  [mp3 @ 0x7f9694011a00] Header missing
  
      Last message repeated 13 times
  
  [mp3 @ 0x7f9694007c00] max_analyze_duration 5000000 reached at 5007020
  
  [mp3 @ 0x7f9694007c00] Estimating duration from bitrate, this may be inaccurate
  
  Input #0, mp3, from 'Sleep Away.mp3':
  
    Metadata:
  
      track           : 3
  
      album           : Bob Acri
  
      artist          : Bob Acri
  
      title           : Sleep Away
  
      genre           : Jazz
  
      album_artist    : Bob Acri
  
      composer        : Robert R. Acri
  
      date            : 2004
  
    Duration: 00:03:21.77, start: 0.000000, bitrate: 192 kb/s
  
      Stream #0.0: Audio: mp3, 44100 Hz, stereo, s16, 192 kb/s
  
  At least one output file must be specified

  The question I am asking is, how can I use the output data above ? I am developiong a music website ; say I want to loop through all the MP3 files and save the info about them into a database, so that the above would result in :

  Sleep Away.mp3    mp3    3:21    Jazz    2004     Bob Acri ...

  obviously in a table

  I have tried to use the php backtick operator with no success so far. I just thought I would put a question up here to get some advice from people that have done something similar.

  Thanks

  Update : I have tried the following

  &lt;?php $output = `ffmpeg -i Sleep\ Away.mp3`; echo "<pre>$output</pre>"; ?>
  
  &lt;?php $output = shell_exec(&#39;ffmpeg -i Sleep\ Away.mp3&#39;); echo "<pre>$output</pre>"; ?>

  both don't appear to return anything.