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• FFprobe command in a var in IF statement

  28 octobre 2017, par bdrilling33

  I am trying to set up a batch file (currently testing in CMD prompt) to run when there is a change in the directory. I have a command stored in a variable "test" which tells me what the first audio codec is. if it isn’t aa3 i plan to re encode the audio with ffmpeg. My first issue is that when i try to run a simple if statement with my var, i get an error.

  set test=ffprobe -v error -select_streams a:0 -show_entries stream=codec_name -of default=nokey=1:noprint_wrappers=1 "my movie (2017).mkv"

  when i run %test% it returns what is expected.

  if i run this as :

  if %test% == "ac3" echo true

  i get :

  -v was unexpected at this time.

  my end goal is to have something like this when something is added to the folder (haven’t go the when something changes part yet...probably just run this once a day idk) :

  set test=ffprobe -v error -select_streams a:0 -show_entries stream=codec_name -of default=nokey=1:noprint_wrappers=1 "%f"
  
  
  
  set outpath=S:\Blu Ray\New folder\"%f"
  
  
  
  for %f in (*.mkv) DO
  
      if %test% <> "ac3" (
  
          ffmpeg -i “%f” -vcodec copy -scodec copy -acodec ac3 -b:a 640k “%outpath%";
  
  del "%f";
  
  move "%outpath%" "s:\Blu Ray\")

  any help would be great

  BD

• OpenCV video capture - output even potentially corrupt frames

  20 juillet 2018, par J. S.

  In FFmpeg, there is a flag "output_corrupt" that allows the command to output even corrupted frames. I am sending h264 stream to a server where its first few frames are corrupted. By setting "output_corrupt" flag in my FFmpeg command, I am able to view the live stream.
  I can see the live stream by piping FFmpeg data to OpenCV VideoCapture (i.e. cv2.VideoCapture(’/dev/stdin’))

  Note : since my plan is to run CV algorithms on those frames, I need to be able to run it on OpenCV.

  However, by not directly sending the data through VideoCapture, it unavoidably causes some latency issue.

  The best scenario would be to just directly send the h264 stream to OpenCV VideoCapture (i.e. cv2.VideoCapture(’udp ://......’))
  However, because of the corrupted frames, the OpenCV script gets stuck after a second.

  Is there any way to run OpenCV VideoCapture such that it still outputs potentially corrupt frames ?

  Thank you.

• 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.