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• Parsing avconv/ffmpeg rawvideo output ?

  23 avril 2013, par DigitalMan

  I'm about to begin a project that will involve working with the output of avconv/ffmpeg, pixel-by-pixel, in rgb32 format. I intend to work with a raw byte stream, such as from the pipe protocol. Basic pointer arithmetic (C/C++) will be used to iterate over these pixels, and modify them in arbitrary manners in real-time.

  I've created a very small file using rawvideo format and codec, and opened it up in a hex editor. As expected, it's just a series of pixels, read right to left, top to bottom. No distinguishing between lines - no problem, if you know how wide the video is beforehand. No distinguishing between frames - no problem, if you also know how tall the video is. No file header for frame rate, or even what the encoding (rgb32, rgb24, yuv, etc.) is - again, as long as you already know, it can be worked with.

  The problem occurs when - for one reason or another - some bytes are missing. Maybe the stream isn't being examined from the beginning, which is likely be the case in my project, or maybe something just got lost. All the pre-existing knowledge in the world (besides maybe a byte count of what's been missed, not gonna happen) won't prevent it from happily chugging along, with an incorrect offset of line and frame.

  So, what I'm looking for is an option for rawvideo, or possibly some other format/codec, that will allow me to work with the resulting stream at the pixel level, in RGB, yet still have a clear definition of where a new frame begins, even if it happens to start "looking" in the middle of a frame. (Width, height, and framerate will indeed be known.)

• ffmpeg doesn't work when called from c++ system

  19 mai 2016, par Arheisel

  I have a c++ script that coneverts a series of jpg into a .mp4 video, the command i use is the folllowing :

  std::system("ffmpeg -threads auto -y -framerate 1.74659 -i /mnt/ev_ramdsk/1/%05d-capture.jpg -vcodec libx264 -preset ultrafast /mnt/ev_ramdsk/1/video.mp4");

  which produces a .mp4 video file like its supposed to except it cant be played from anywhere (tested in 2 computers and html5 video)

  But, if from the same computer where the program runs, i do :

  ffmpeg -threads auto -y -framerate 2 -i %05d-capture.jpg -vcodec libx264 -preset ultrafast video.mp4

  from the command line, the output video plays wonderfully (except in vlc, for vlc i have to use -vcodec mpeg4)

  What can possibly cause this behaviour ?
  could cp command corrupt the file ? (ran after the mpeg to move it out of the ramfs)

  EDIT :

  As requested, i ran the whole set of commands one by one in the console exactly as the program do (the program logs every single command it runs, i just repeated them).

  The commands are :

  cp -r /var/cache/zoneminder/events/1/16/05/18/23/30/00/ /mnt/ev_ramdsk/1/
  
  ffmpeg -threads auto -y -framerate 1.76729 -i /mnt/ev_ramdsk/1/%5d-capture.jpg -preset ultrafast /mnt/ev_ramdsk/1/video.mp4
  
  cp /mnt/ev_ramdsk/1/video.mp4 /var/cache/evmanager/videos/1/2016_05_18_23_30_00_.mp4

  The resulting .mp4 file can be played without any trouble. Also, is the only one with a preview image in the file explorer.

  Thank you very much !

• Ffmpeg- Split the video into 30 seconds chunks in android [duplicate]

  23 novembre 2019, par Corgi Mogi

  This question is an exact duplicate of :

  • Ffmpeg- Split video into 30 seconds parts in android

  I am trying to split a video file into 30 second blocks.
  I do not need to specify where the 30 seconds start or finish.
  EXAMPLE- A single 45 second video will be split into VID1_part1 (30 seconds), VID1_part2 (15 seconds).

  Right now I am using the Ffmpeg command where I need to specify the starting and ending point.

  String[] complexCommand = {"-ss", "" + startMs / 1000, "-y", "-i", yourRealPath, "-t", "" + (endMs - startMs) / 1000,"-vcodec", "mpeg4", "-b:v", "2097152", "-b:a", "48000", "-ac", "2", "-ar", "22050", filePath};

  I also tried to add a for loop in order to repeat the process

   int start, end;
  
          for (int i = 0; i <= duration; i = i + 30) {
  
              start = i;
  
              end = start + 30;
  
  
  
              String[] complexCommand = {"-ss", "" + start, "-y", "-i", yourRealPath, "-t", "" + end,"-vcodec", "mpeg4", "-b:v", "2097152", "-b:a", "48000", "-ac", "2", "-ar", "22050", filePath};
  
              execFFmpegBinary(complexCommand);
  
          }

  But didn’t workout

  This works fine.
  But I want the command through I can split a single video into 30 second chunks.
  And should I use a single command for this purpose or a series of commands ?
  Help is much appreciated