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• Using ffprobe to get number of keyframes in raw AVI file *without* processing entire file ?

  26 juillet 2018, par aggieNick02

  This question and answer cover how to get the framecount and keyframe count from an AVI file, which is very useful. I’ve got a raw AVI file and want to count the number of keyframes (equivalent to non-dropped frames for raw AVI), but it takes a long time to process through a raw AVI file.

  There is some way to get this information without fully processing the file, as VirtualDub provides both framecount and key framecount in the file information, as well as total keyframe size, almost instantly for a 25-second raw 1920x1080 AVI. But ffprobe requires count_frames to populate nb_read_frames, which takes some good processing time.

  I can do some math with the file’s size and the frame’s width/height/format to get a fairly good estimate of the number of frames, but I’m worried the overhead of the container could be enough to throw the math off for very short clips. (For my 25 second clip, I get 1286.12 frames, when there are really 1286.)

  Any thoughts on if there is a way to get this information programatically with ffprobe or ffmpeg without processing the whole file ? Or with another API on windows ?

• ffmpeg avcodec_find_encoder_by_name failes to find encoder h264_nvenc

  18 septembre 2018, par Yona

  When I run this command "ffmpeg -h encoder=h264_nvenc" in the terminal it gives me the following output
  

  and I am able to use the encoder through the command line interface but it got a problem when I try to run from the following source code.

  #include <iostream>
  
  #include 
  
  #include 
  
  
  
  extern "C"
  
  {
  
  #include <libavcodec></libavcodec>avcodec.h>
  
  #include <libavformat></libavformat>avformat.h>
  
  #include <libavutil></libavutil>imgutils.h>
  
  #include <libavutil></libavutil>mathematics.h>
  
  #include <libavutil></libavutil>opt.h>
  
  #include <libswscale></libswscale>swscale.h>
  
  #include 
  
  }
  
  
  
  int main( int argc, char** argv )
  
  {
  
  
  
      const AVCodec *codec;
  
      AVCodecContext *c= NULL;
  
  
  
      av_register_all();
  
  
  
      std::cout &lt;&lt; "Loading codec" &lt;&lt; std::endl;
  
  
  
  //    codec = avcodec_find_encoder_by_name( "libx264" ); // works
  
      codec = avcodec_find_encoder_by_name( "h264_nvenc" );
  
     // codec = avcodec_find_decoder_by_name( "h264_cuvid" );
  
      if( !codec )
  
      {
  
          throw std::runtime_error( "Unable to find codec!" );
  
      }
  
  
  
      std::cout &lt;&lt; "Allocating context" &lt;&lt; std::endl;
  
  
  
      return 0;
  
  
  
  }</iostream>

• Using ffmpeg in node, without using fluent-ffmpeg

  16 mai 2018, par drexdelta

  I am using ffmpeg without using fluent-ffmpeg. I am using ’child_process’ from node.

  First of all I verified how can I pass more than one arguments to the child process command. and I verified it given below code.

  I used copy command like this

  cp vid1.mp4 vid2.mp4

  which successfully copied vid1 into vid2.

  const execFile = require('child_process').execFile;
  
  const child = execFile('cp', ['vid1.mp4', 'vid3.mp4'], (error, stdout, stderr) => {
  
      if (error) {
  
          console.error('stderr: =============================', stderr);
  
          throw error;
  
      }
  
      console.log('stdout: ==========================', stdout);
  
  });
  
  
  
  console.log('here');

  Above code is content of the ’index.js’(default entry point in node). And running this with node . , which copies vid1 into vid3 successfully.

  Now, I want to do watermarking to the given video. For that I am using this tutorial. Currently link to the actual tutorial is broken, you can see it here.

  This is the command that I am using

  ffmpeg -i input.mp4 -i logo.png -filter_complex "overlay=10:10" output.mp4

  Now the same command I am using like this ,

  const execFile = require('child_process').execFile;
  
  
  
  const child = execFile('ffmpeg', ['-i', 'input.mp4' , '-i' , 'logo.png' , '-filter_complex' , '"overlay=10:10"' , 'output.mp4' ], (error, stdout, stderr) => {
  
      if (error) {
  
          console.error('stderr: =============================', stderr);
  
          throw error;
  
      }
  
      console.log('stdout: ==========================', stdout);
  
  });
  
  
  
  console.log('here');

  and I am getting an error , that ,

  No such filter : ’"overlay’ Error initializing complex filters. Invalid
  argument

  /Users/neerpatel/Desktop/testProjects/childProcess/index.js:7
  throw error ;
  ^

  Error : Command failed : ffmpeg -i input.mp4 -i logo.png
  -filter_complex "overlay=10:10" output.mp4

  You can clearly see that the same command that runs in terminal directly, doesn’t work when I pass it in child process. Why does it happen ?

  Moreover, I wanted to add tag ’watermarking’ , but I can’t create tag since my reputation is below 1500. please, someone do it.

  UPDATE :
  I used EXEC , instead of execFile . and it worked like charm, but parent file kept waiting for child process. Child process never returns END signal. and this is my code.

  const exec = require('child_process').exec;
  
  
  
  const child = exec('ffmpeg -i input.mp4 -i logo.png -filter_complex "overlay=10:10" output.mp4', (error, stdout, stderr) => {
  
      if (error) {
  
          console.error('stderr: =============================', stderr);
  
          throw error;
  
      }
  
      console.log('stdout: ==========================', stdout);
  
  });
  
  
  
  console.log('here');