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• How to make video loop properly ?

  28 mai 2019, par woopwoop399

  I want to play this video in a loop https://www.nicovideo.jp/watch/sm16617386 . I want to play an mp4 file in such a way, that whenever it gets to some point in the video (let’s say, 30.3 seconds), it will loop back (to for example 5.85 seconds).

  I tried to add this code in ffplay.c , it didn’t work well enough, I can hear the transition. I guess seeking isn’t fast enough, or audio needs to be looped in an independant way somehow.

  static void video_refresh(void *opaque, double *remaining_time)
  
  {
  
     (original code here...)
  
      time = get_master_clock(is);
  
      if (isnan(time))
  
          time = (double)is->seek_pos / AV_TIME_BASE;
  
      if (time > jump_when) {
  
          stream_seek(is, (int64_t)(6.0 * AV_TIME_BASE), (int64_t)(0.0 * AV_TIME_BASE), 0);
  
      }
  
  }

  My current plan is to just dig into ffmpeg, understand how video and audio decoders work, and savestate/loadstate the decoders.

• How do I use find and ffmpeg to batch convert a bunch of .flac files to .mp3 ?

  30 avril 2019, par Keith

  I have a directory with a bunch of .flac files that I need to convert to .mp3. I plan to use ffmpeg from the command line to do the conversions and I’d like to avoid doing this manually for every file. I’m familiar with the find command but I’m having difficulty using it with ffmpeg which requires both input and output filenames. I imagine using something like

  find . -name "*.flac" -exec ffmpeg -i {}.flac {}.mp3 +

  But of course this doesn’t work. For one thing it fails to strip prefixes and suffixes from the filename being passed to ffmpeg.

  Please also note that the filenames include whitespace so the solution has to ignore whitespace successfully. I’m also on OS X having built ffmpeg with homebrew.

• How to convert images to video using FFMpeg for embedded applications ?

  19 avril 2019, par zthatch56

  I’m encoding images as video using FFmpeg using custom C code rather than linux commands because I am developing the code for an embedded system.

  I am currently following through the first dranger tutorial and the code provided in the following question.

  How to encode a video from several images generated in a C++ program without writing the separate frame images to disk ?

  I have found some "less abstract" code in the following github location.

  https://github.com/FFmpeg/FFmpeg/blob/master/doc/examples/encode_video.c

  And I plan to use it as well.

  My end goal is simply to save video on an embedded system using embedded C source code, and I am coming up the curve too slowly. So in summary my question is, Does it seem like I am following the correct path here ? I know that my system does not come with hardware for video codec conversion, which means I need to do it with software, but I am unsure if FFmpeg is even a feasible option for embedded work because I am yet to compile.

  The biggest red flag for me thus far is that FFmpeg uses dynamic memory allocation. I am unfamiliar with how to assess the amount of dynamic memory that it uses. This is very important information to me, and if anyone is familiar with the amount of memory used or how to assess it before compiling, I would greatly appreciate the input.