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• Streaming ffmpeg from fifo file starts only when i close the fifo file

  23 juin 2022, par tamirg

  Im starting an ffmpeg process, where the input is a FIFO file i created.
Im writing some data in a loop to the FIFO file, but the ffmpeg process doesn't start streaming until one of the two happens :

  


  

  1. i'm closing the file

  


  2. iv'e written a certain amount of data. after a while of writing, the ffmpeg process starts streaming. The more data i write, the faster it starts running. (im writing a chunk of data on each loop, if i just duplicate those chunks times 100, it starts much faster).

  


  


  What can be the reason for that ? Is there a minimum of data required for the ffmpeg process to start streaming ? How can i "force" it to start, without closing the FIFO file after writing ?

  


• How can I convert WebM file to WebP file with transparency ?

  24 août 2020, par c-an

  I tried it with ffmpeg.

  


  ffmpeg input.webm output.webp


  


  input.webm contains transparent background and But the alpha channel becomes white in webp. I think that means alpha channel doesn't come together.

  


  I extracted frames with this command :

  


  ffmpeg -i input.xxx -c:v libwebp output_%03d.webp


  


  And it also gives me webp files with white background.

  


  How can I convert it properly with alpha channel ? OR should I convert it from other format(extension) ?

  


• '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
  
   }