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• 'C' program to pipeout audio file to FFMPEG and generate Video file

  9 mai 2017, par soflow

  I am attempting to write a short ’C’ program which reads in an Audio file using FFMPEG, processes that file using a ’C’ program, and then outputs a file via FFMEPG, which combines the new, modified audio together with a Video representation using the FFMPEG showwaves filter.

  At present the program attempts to do the following :-

  i) Read in an audio file, using pipein thorugh FFMPEG
  ii) Process the audio file using a portion of the ’C’ program
  iii) Pipeout the modified audio to FFMPEG, and generate a file using the ’showwaves’ filter in FFMEPG to create an MP4 file with audio and video.

  The following code run form the ommand line in FFMPEG generates the Audio/Video MP4 I want to create :-

  ffmpeg -y -f s16le -ar 44100 -ac 1 -i 12345678.wav  -i 12345678.wav  -filter_complex  "[0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  12345678.mp4

  "

  This code generates a processed audio file, and outputs it to a .wav file as required :-

  #include 
  
  #include 
  
  #include 
  
  
  
  void main()
  
  {
  
  // Launch two instances of FFmpeg, one to read the original WAV
  
  // file and another to write the modified WAV file. In each case,
  
  // data passes between this program and FFmpeg through a pipe.
  
  FILE *pipein;
  
  FILE *pipeout;
  
  pipein  = popen("ffmpeg -i 12345678.wav -f s16le -ac 1 -", "r");
  
  pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i - out.wav", "w");
  
  
  
  // Read, modify and write one sample at a time
  
  int16_t sample;
  
  int count, n=0;
  
  while(1)
  
  {
  
      count = fread(&sample, 2, 1, pipein); // read one 2-byte sample
  
      if (count != 1) break;
  
      ++n;
  
      sample = sample * sin(n * 5.0 * 2*M_PI / 44100.0);
  
      fwrite(&sample, 2, 1, pipeout);
  
  }
  
  
  
  // Close input and output pipes
  
  pclose(pipein);    
  
  pclose(pipeout);
  
  }

  (This code borrowed from ted Burke’s excellent post here)

  I have made an attempt as shown below, but this is not working :-

  #include 
  
  #include 
  
  #include 
  
  
  
  void main()
  
  {
  
  // Launch two instances of FFmpeg, one to read the original WAV
  
  // file and another to write the modified WAV file. In each case,
  
  // data passes between this program and FFmpeg through a pipe.
  
  FILE *pipein;
  
  FILE *pipeout;
  
  pipein  = popen("ffmpeg -i 12345678.wav -f s16le -ac 1 -", "r");
  
  pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i 12345678.wav  -i 
  
  12345678.wav  -filter_complex  "
  
  [0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" 
  
  -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -
  
  codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  
  
  12345678.mp4
  
  ", "w");
  
  
  
  
  
  // Read, modify and write one sample at a time
  
  int16_t sample;
  
  int count, n=0;
  
  while(1)
  
  {
  
      count = fread(&sample, 2, 1, pipein); // read one 2-byte sample
  
      if (count != 1) break;
  
      ++n;
  
      sample = sample * sin(n * 5.0 * 2*M_PI / 44100.0);
  
      fwrite(&sample, 2, 1, pipeout);
  
  }
  
  
  
  // Close input and output pipes
  
  pclose(pipein);    
  
  pclose(pipeout);
  
  }    

  Ideally someone can suggest an improved version of the pipeout command above - alternately another process to achieve this would be interesting

  * EDIT *

  Thanks to @Mulvya, the revised pipeout line is now :-

  pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i -  -filter_complex  "[0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  12345678.mp4

  ", "w") ;

  On compiling with gcc I get the following error messages :-

  avtovid2.c: In function \u2018main\u2019:
  
  
  
  wavtovid2.c:13:83: error: expected \u2018]\u2019 before \u2018:\u2019 
  
  token
  
   pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i -  -
  
  filter_complex  "
  
  [0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" 
  
  -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -
  
  codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  
  
  12345678.mp4
  
  
  
  ^
  
  wavtovid2.c:13:86: error: expected \u2018)\u2019 before 
  
  \u2018showwaves\u2019
  
   pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i -  -
  
  filter_complex  "
  
  [0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" 
  
  -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -
  
  codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  
  
  12345678.mp4
  
  
  
  ^
  
  wavtovid2.c:13:98: error: invalid suffix "x720" on integer constant
  
   pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i -  -
  
  filter_complex  "
  
  [0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" 
  
  -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -
  
  codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  
  
  12345678.mp4
  
  
  
  ^
  
  wavtovid2.c:13:153: warning: missing terminating " character
  
   pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i -  -
  
  filter_complex  "
  
  [0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" 
  
  -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -
  
  codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  
  
  12345678.mp4
  
  
  
  ^
  
  wavtovid2.c:13:86: error: missing terminating " character
  
   pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i -  -
  
  filter_complex  "
  
  [0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" 
  
  -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -
  
  codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  
  
  12345678.mp4
  
  
  
  ^
  
  wavtovid2.c:14:6: warning: missing terminating " character
  
   ", "w");
  
    ^
  
  wavtovid2.c:14:1: error: missing terminating " character
  
   ", "w");
  
   ^
  
  wavtovid2.c:13:21: warning: passing argument 1 of \u2018popen\u2019 makes 
  
  pointer from integer without a cast
  
   pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i -  -
  
  filter_complex  "
  
  [0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" 
  
  -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -
  
  codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  
  
  12345678.mp4
  
                   ^
  
  In file included from wavtovid2.c:1:0:
  
  /usr/include/stdio.h:872:14: note: expected \u2018const char *\u2019 but 
  
  argument is of type \u2018char\u2019
  
   extern FILE *popen (const char *__command, const char *__modes) __wur;
  
            ^
  
  wavtovid2.c:13:15: error: too few arguments to function \u2018popen\u2019
  
   pipeout = popen("ffmpeg -y -f s16le -ar 44100 -ac 1 -i -  -
  
  filter_complex  "
  
  [0:a]showwaves=s=1280x720:mode=line:rate=25,format=yuv420p[v]" -map "[v]" 
  
  -map 1:a:0 -codec:v libx264 -crf 21 -bf 2 -flags +cgop -pix_fmt yuv420p -
  
  codec:a aac -strict -2 -b:a 384k -r:a 48000 -movflags faststart  
  
  12345678.mp4
  
             ^ 
  
  In file included from wavtovid2.c:1:0:
  
  /usr/include/stdio.h:872:14: note: declared here
  
   extern FILE *popen (const char *__command, const char *__modes) __wur;
  
            ^
  
  wavtovid2.c:32:1: error: expected \u2018;\u2019 before \u2018}\u2019 
  
  token
  
   }

• No such file or directory Error with FFMPEG + CarrierWave screenshot method

  10 juillet 2013, par dodgerogers747

  I am using AWS CORS to upload videos to my site, all of which works as planned.

  I have the following model method which runs as an after_create callback (for speed) to take a screenshot from the video file on AWS. I plan to move this out into a delayed job but I don't think this will solve this particular issue. Please advise if mistaken.

  I use FFMPEG to take a screenshot from the AWS self.file location, I then send the file to CarrierWave by saving the file to self.screenshot where it is uploaded to AWS.

  Approx. 50% of the time it errors out with Errno::ENOENT - No such file or directory for the location of the screenshot image.

  How can I rectify my code to remove this error and how come it only occurs around 50% of the time ? If anyone needs more code just shout.

  video.rb

  after_create :take_screenshot
  
  
  
  mount_uploader :screenshot, ImageUploader
  
  
  
    def take_screenshot
  
      location = "#{Rails.root}/public/uploads/tmp/screenshots/#{unique}_#{File.basename(file)}.jpg"
  
      system `ffmpeg #{log_level} -i #{self.file} -ss 00:00:0#{time_frame} -vframes 1 #{location}`
  
      logger.debug "Trying to take screenshot from #{self.file}"
  
      #pass the actual file to CarrierWave to handle the image upload
  
      self.screenshot = File.open(location)
  
      self.save
  
      logger.debug "Deleting tmp file: #{location}: #{File.delete(location)}" if self.screenshot.present?
  
    end
  
  
  
  def unique
  
      (0..6).map{(65+rand(26)).chr}.join
  
    end
  
  
  
  def log_level
  
      "-loglevel panic"
  
    end
  
  
  
    def time_frame
  
      rand(0..3)
  
    end

  Stack trace :

  Started POST "/videos" for 127.0.0.1 at 2013-07-10 03:58:49 +0800
  
  Processing by VideosController#create as JS
  
    Parameters: {"utf8"=>"✓", "authenticity_token"=>"6M1Ia+Ag2E3HVKH2PO/p7jewxSpMPdWeVHGA933Bzjw=", "video"=>{"file"=>"http://bucketname.s3.amazonaws.com/uploads/video/file/671a87fb-91de-4eaf-a38a-1b25c51798e5/Good_7iron.m4v"}}
  
    User Load (0.3ms)  SELECT `users`.* FROM `users` WHERE `users`.`id` = 9 LIMIT 1
  
     (0.1ms)  BEGIN
  
    SQL (0.2ms)  INSERT INTO `videos` (`created_at`, `file`, `question_id`, `screenshot`, `updated_at`, `user_id`) VALUES ('2013-07-09 19:58:49', 'http://bucketname.s3.amazonaws.com/uploads/video/file/671a87fb-91de-4eaf-a38a-1b25c51798e5/Good_7iron.m4v', NULL, NULL, '2013-07-09 19:58:49', 9)
  
  Trying to take screenshot from http://bucketname.s3.amazonaws.com/uploads/video/file/671a87fb-91de-4eaf-a38a-1b25c51798e5/Good_7iron.m4v
  
     (0.8ms)  ROLLBACK
  
  Completed 500 Internal Server Error in 3550ms
  
  
  
  Errno::ENOENT - No such file or directory - /Users/me/rails/project/public/uploads/tmp/screenshots/WCACLIC_Good_7iron.m4v.jpg:
  
    app/models/video.rb:24:in `initialize'
  
    app/models/video.rb:24:in `open'
  
    app/models/video.rb:24:in `take_screenshot'

• file : Add an option for following a file that is being written

  5 février 2015, par Martin Storsjö

  file : Add an option for following a file that is being written
  Using this requires setting the rw_timeout option to make it
  
  terminate, alternatively using the interrupt callback (if used via
  
  the API).
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] doc/protocols.texi
  • [DBH] libavformat/file.c
  • [DBH] libavformat/version.h