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• Golang and ffmpeg realtime streaming input/output

  25 avril 2017, par Anderson Scouto da Silva

  I’m new to Go !

  I’m doing a simple test that is reading the output from ffmpeg and writing to a file.

  I know I can do it in a different way, simply convert, but this is the beginning of a project where I want to later manipulate the bytes read, changing them and then sending them to the output. And the input will be UDP and output will be UDP too, that is, I will get the ffmpeg output I will treat the bytes as I wish to do and then I will throw these bytes as input into another ffmpeg process which output is UDP as well.

  With this simple test the result of the file does not run in VLC, I believe I’m writing the bytes in the output file correctly, but the output file always has 1MB less than the input file.

  I would like some help to elucidate what would be the best way to write this test that I am doing, based on that I can get out of the place. I do not know if it’s exactly wrong, but I have the impression that it is.

  The input file is a video in 4K, h264, I believe the output should be the same, because in this simple test I am simply reading what goes out in the cmd writing in the file.

  Follow the code for analysis :

  package main
  
  
  
  import (
  
      "os/exec"
  
      "os"
  
  )
  
  
  
  func verificaErro(e error) {
  
      if e != nil {
  
          panic(e)
  
      }
  
  }
  
  
  
  func main() {
  
      dir, _ := os.Getwd()
  
  
  
      cmdName := "ffmpeg"
  
      args := []string{
  
          "-hide_banner",
  
          "-re",
  
          "-i",
  
          dir + "\\teste-4k.mp4",
  
          "-preset",
  
          "superfast",
  
          "-c:v",
  
          "h264",
  
          "-crf",
  
          "0",
  
          "-c",
  
          "copy",
  
          "-f", "rawvideo", "-",
  
      }
  
      cmd := exec.Command(cmdName, args...)
  
  
  
      stdout, err := cmd.StdoutPipe()
  
      verificaErro(err)
  
      err2 := cmd.Start()
  
      verificaErro(err2)
  
  
  
      fileOutput := dir + "/out.raw"
  
      var _, err3 = os.Stat(fileOutput)
  
  
  
      if os.IsNotExist(err3) {
  
          var file, err = os.Create(fileOutput)
  
          verificaErro(err)
  
          defer file.Close()
  
      }
  
  
  
      f, err4 := os.OpenFile(dir+"/out.raw", os.O_RDWR|os.O_APPEND, 0666)
  
  
  
      verificaErro(err4)
  
  
  
      bytes := make([]byte, 1024)
  
      for {
  
          _, err5 := stdout.Read(bytes)
  
          if err5 != nil {
  
              continue
  
          }
  
          if len(bytes) > 0 {
  
              _, err6 := f.Write(bytes)
  
              verificaErro(err6)
  
          } else {
  
              break
  
          }
  
      }
  
  
  
      f.Close()
  
  }

• In method chaining, how to realize response in a JavaScript callback ?

  13 avril 2017, par CHBS

  I write for myself a module on node js, I can not implement the save() function

  module.exports = function(filename, callback){
  
      this.callback = callback(require(filename));
  
      return { 
  
          save: function() {
  
              console.log(this);
  
              //fs.writeFile(filename, 'Hello Node.js');
  
          }
  
      }; 
  
  }
  
  
  
  File('file.json', function(data){
  
      data['blablabla'] = 12345;
  
  }).save();

  How from a callback, to transfer the changed copy of a file in save (), and there already to save it through fs ?
  I’m interested in the implementation of the fluent-ffmpeg function save ()

  ffmpeg('/path/to/file.avi')
  
   .videoCodec('libx264')
  
   .audioCodec('libmp3lame')
  
   .size('320x240')
  
   .on('error', function(err) {
  
     console.log('An error occurred: ' + err.message);
  
   })
  
   .on('end', function() {
  
     console.log('Processing finished !');
  
   })
  
   .save('/path/to/output.mp4');

  And as well as implemented on() ?

  on('end'),   
  
  on('error'),   
  
  on('response'),

  I will be grateful for the information provided.

• Can the outputFile of MediaRecorder be a named pipe ?

  13 avril 2017, par Harrison

  Following
  Android Camera Capture using FFmpeg
  and
  feed raw yuv frame to ffmpeg with timestamp

  I successfully put raw frames of Android phone camera into a named pipe made by mkfifo, and used ffmpeg to process them and generated a video file.

  But the problem is that by ffmpeg, the encoding is very slow, it can only process 3 5 frames per second. The reason I have to use ffmpeg instead of MediaRecorder is that later I need to use ffmpeg to generate HLS segments and m3u8 file.

  So I have to turn to use native encoder like MediaRecorder and try to set its OutputFile to a named pipe following
  How to use unix pipes in Android

  My code likes this,

  private String pipe = "/data/data/com.example/v_pipe1";
  
  ...
  
  mMediaRecorder.setOutputFile(pipe);
  
  ...
  
  mMediaRecorder.start();

  Also I have a ffmpeg thread to use this pipe as the input.

  But when I call mMediaRecorder.start() ; It will throw java.lang.IllegalStateException. I’ve tried to put ffmpeg thread before or after calling mMediaRecorder.start(), but with the same error.

  I have no idea about this now. Could someone tell me how to solve this ?
  Any suggestions are welcome and appreciated. Thanks.