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• Generate new video from selected seconds of a longer video

  27 juin 2018, par martins

  I try to generate a shorter version of a 10min original videofile.mp4 that includes only four 10s subclips of the original file (i.e. from seconds 10 to 20 ;197 to 207 ;393 to 403 ;570 to 580). So far I could only generate 4 new files copying both video and audio :

  ffmpeg -i videofile.mp4 -vcodec copy -acodec copy -ss 10 -to 20 videofile1.mp4 -vcodec copy -acodec copy -ss 197 -to 207 videofile2.mp4 -vcodec copy -acodec copy -ss 393 -to 403 videofile3.mp4 -vcodec copy -acodec copy -ss 570 -to 580 videofile4.mp4

  However, I am having deep trouble in concatenating those 4 subclips to generate the desired 40seconds out_videofile.mp4. I found this alternative approach using the "select" command in ffmpeg which saves me of my "failed" concatenation process. So far I have :

  ffmpeg -i videofile.mp4 -vf "select='between(t,10,20)+between(t,197,207)+between(t,393,403)+between(t,570,580)',setpts=N/FRAME_RATE/TB" -af "aselect='between(t,10,20)+between(t,197,207)+between(t,393,403)+between(t,570,580)" out_videofile.mp4

  I guess this last code should give me the 40s out_videofile.mp4 I want. However, it gives me a "SyntaxError : invalid syntax". Any idea where I go wrong ?

  Thanks for your time anyways.

• ffmpeg puts black frames in the first few seconds of the video

  30 juin 2018, par Joe T. Boka

  I am adding an audio file to a video file, using ffmpy, which is a python wrapper for ffmpeg.

  The input audio file voice.wave and the input video file video.avi are the same length.

  When I use the below code, the output video output.ts contains both audio and video, as expected. The problem : the audio is running fine, but the first few seconds of the output video output.ts is black.

  from ffmpy import FFmpeg
  
  ff = FFmpeg(inputs={'video.avi': None, 'voice.wav': None}, outputs={'output.ts': '-c:v h264 -c:a ac3'})
  
  ff.cmd
  
  'ffmpeg  -i voice.wave -i video.avi -c:v h264 -c:a ac3 output.ts'
  
  ff.run()

• Write, with ffmpeg, every 30 seconds wav file from ip stream to file.temp and change the name to timestamp.wav after

  18 juillet 2018, par Eliya

  I’m using ffmpeg to record IP stream and write every 30 seconds to wav file.

  Here is my bash script code :

  #!/bin/bash
  
  function start_ffmpeg_stream ()
  
  {
  
      address=$1 #This is IP stream address
  
      ffmpeg_option=$2 # "?overrun_nonfatal=1&fifo_size=250000"
  
      folder_name=$3 #folderName
  
      channel_number=$4 #i
  
      #local pid      
  
      ffmpeg  -loglevel 8 -thread_queue_size 1500 -i "$address$ffmpeg_option" -c copy\
  
          -vn -f segment -segment_time 30 -ar 8000 -acodec pcm_s32le -ac 1 -strftime 1 /"$folder_name"/"X$channel_number""_""%s.wav"&     
  
      pid=$!
  
      echo "$Start ffmpeg, pid is - $pid" 
  
      __="$pid"
  
  }
  
  ffmpegOptions="?overrun_nonfatal=1&fifo_size=250000"
  
  folderName="/wav_files"
  
  start_ffmpeg_stream "udp://224.10.0.1"  "$ffmpegOptions" "$folderName" "1"

  Now the wav file name is like "X000001_unix_time_stamp.wav".

  I want to write the file name in writeing time something like "X000001_unix_time_stamp.temp"

  And when the 30 seconds done and the FFmpeg finish to write this 30 seconds, I want that FFmpeg changes the name to "X000001_unix_time_stamp.wav"

  And keep writing next 30 seconds.

  The only change that i want is, when FFmpeg writing it write in temp name and after FFmpeg finish to write it change the name.

  It’s seem to case when i donloaded a file so until the donload not finish the file has a temp name and when it done the name change to const name.