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• How to pipe rgba data using Node.js to ffmpeg ?

  7 juillet 2015, par Swoth

  Context
  I am developing a small programm that is supposed to render a video, as fast as possible, based on frames captured from a canvas. The animation is rendered to a headless canvas implementation using Rekapi (JavaScript animation framework). The headless canvas is a Node.js module called node-canvas by Automattic. The animation frames are rendered one after another, after each rendering the frame is retrieved using canvas.getImageData().data (Uint8ClampedArray - rgba, faster than canvas.toDataUrl) and put into an array. Every frame is supposed to be send to ffmpeg to create a video.

  Rekapi -> canvas -> getImageData -> array -> ffmpeg

  Problem
  Everything except the transfer of stored rgba-array-data to ffmpeg works. I don’t seem to manage the transport using Node.js. How do I pass my frames to ffmpeg using Node.js and what did I do wrong ?

  What I do
  The code below renders and saves each frame as rgba data to an array. The renderScene-function renders each animation frame.

  console.log("Rendering getImageData, length:"+ videoLength);
  
  var dataArray = [];
  
  function imageDataCallback() {
  
      dataArray.push(context.getImageData(0, 0, 1280, 720).data);
  
  }
  
  rekapi.on('afterUpdate', imageDataCallback);
  
  
  
  var time = Date.now();
  
  renderScene(rekapi);
  
  console.log('Time used: ' + (Date.now() - time) + 'ms;');
  
  rekapi.off('afterUpdate', imageDataCallback);

  I already tried various possibilities to pipe that data to ffmpeg. In general I created a child process in Node.js executing ffmpeg :

  var spawn = require('child_process').spawn;    
  
  var child = spawn('ffmpeg', [
  
          '-pix_fmt', 'rgba',
  
          '-s','1280x720',
  
          '-r', 25,
  
          '-f', 'rawvideo',
  
          '-vcodec', 'rawvideo',
  
          '-i', '-', // read frames from stdin
  
          '-threads', 0, // use all cores
  
          'test.mpg']);

  I also tried using -i pipe:0, which is the same as -i -, just to be sure.
  After process creation i registered for various events to know what happens :

   child.on('error', function(error){
  
      console.log(error);
  
  });
  
  child.stdin.on('data', function (data) {
  
      console.log('data retrieved')
  
  });
  
  child.on('exit', function (code) {
  
      console.log('child exit with code:' + code)
  
  });

  Now I write my array data to the child’s stdin :

  for(var i = 0; i < dataArray.length; ++i){
  
      var buffer = new Buffer(dataArray[i]);
  
      child.stdin.write(buffer);
  
      console.log('wrote: ' + i);
  
  }

  I wrote 25 frames this way. The console displays the following :

  wrote: 24
  
  wrote: 25
  
  events.js:85
  
        throw er; // Unhandled 'error' event
  
              ^
  
  Error: read ECONNRESET
  
      at exports._errnoException (util.js:746:11)
  
      at Pipe.onread (net.js:559:26)

  ffmpeg generated a 0 byte test.mpg and as it seems no definded child-callback (like data) except error has been called. I am not 100% sure about the lifecycle but, as I understood, data should be called each time I write something.

  I am very new to Node.js, thus I might not understand the big picture of it’s child processes.

  Since my reputation is too low I am not allowed to post more than 2 links (first question) and I don’t feel comfortable using non-typed languages like JavaScript.

• FFmpegMediaPlayer : findLibrary returned null

  8 août 2015, par IceJOKER

  I use https://github.com/wseemann/FFmpegMediaPlayer in my applicaton, but some Adndroid device throw exception :

  java.lang.ExceptionInInitializerError
  
  at ru.mypackage.PlayService.initPlayer(PlayService.java:74)
  
  at ru.mypackage.PlayService.onCreate(PlayService.java:68)
  
  at android.app.ActivityThread.handleCreateService(ActivityThread.java:1949)
  
  at android.app.ActivityThread.access$2500(ActivityThread.java:117)
  
  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:989)
  
  at android.os.Handler.dispatchMessage(Handler.java:99)
  
  at android.os.Looper.loop(Looper.java:130)
  
  at android.app.ActivityThread.main(ActivityThread.java:3687)
  
  at java.lang.reflect.Method.invokeNative(Native Method)
  
  at java.lang.reflect.Method.invoke(Method.java:507)
  
  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:867)
  
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:625)
  
  at dalvik.system.NativeStart.main(Native Method)
  
  Caused by: java.lang.UnsatisfiedLinkError: Couldn't load avutil: findLibrary returned null
  
  at java.lang.Runtime.loadLibrary(Runtime.java:429)
  
  at java.lang.System.loadLibrary(System.java:554)
  
  at wseemann.media.FFmpegMediaPlayer.<clinit>(FFmpegMediaPlayer.java:620)
  
  ... 13 more
  
  </clinit>

  My project :
  

  [![enter image description here][3]][3]

  Can somebody explain me what’s wrong there ?
  On my device and some other device the app working nice, but on some device (for example : Galaxy Ace (GT-S5830i) Android 2.3.3 - 2.3.7) it throw the exception.

  p.s. about "lib" prefix I understood ( http://developer.android.com/intl/ru/reference/java/lang/System.html#mapLibraryName(java.lang.String) )

• FFmpeg memory growing in avcodec_decode_video2

  21 juillet 2015, par Wendy Pan

  I am using C# to call the ffmpeg lib.
  I use the example code to decode an video in the MP4 format.

  However, I found out that the memory grows a lot (like 10MB), when I called the avcodec_decode_video2 function.

  The memory keeps growing until I called the avcodec_close(&CodecContext) function.

  I suppose the reason may be that AVCodecContext alloc 10MB data during the call of avcodec_decode_video2 function. And this memory will not be released until the AVCodecContext is closed.

  I do not know if I am right.

  Main codes are in the following.

  private bool readNextBuffer(int index)
  
      {
  
          /// Read frames into buffer
  
          //m_codecContext->refcounted_frames = 0;
  
          int frameNumber = 0;
  
          FrameBuffer[index].Clear();
  
          GC.Collect();
  
  
  
          while (frameNumber < m_bufferSize)
  
          {
  
              AVPacket Packet; /// vedio packet 
  
              AVPacket* pPacket = &Packet;
  
              //AVFrame* pDecodedFrame = FFmpegInvoke.avcodec_alloc_frame(); 
  
              AVFrame* pDecodedFrame = FFmpegInvoke.av_frame_alloc(); 
  
              if (FFmpegInvoke.av_read_frame(m_pFormatContext, pPacket) < 0)
  
              {
  
                  Console.WriteLine("The end of the vedio.");
  
                  break;
  
              }
  
              if (pPacket->stream_index == pStream->index)
  
              {
  
                  /// Decode vedio frame
  
                  int gotPicture = 0;
  
                  int size = FFmpegInvoke.avcodec_decode_video2(m_codecContext, pDecodedFrame, &gotPicture, pPacket);
  
                  if (size < 0)
  
                  {
  
                      Console.WriteLine("End of the vedio.");
  
                      //throw new Exception(string.Format("Error while decoding frame {0}", frameNumber));
  
                      break;
  
                  }
  
  
  
                  if (gotPicture == 1)
  
                  {
  
                      /// Allocate an AVFrame structure
  
  
  
                      if (convertFrame(pDecodedFrame, index))
  
                      {
  
                          frameNumber++;
  
                      }
  
                      else
  
                      {
  
                          Console.WriteLine("Error: convert failed.");
  
                      }
  
                  }
  
              }
  
              FFmpegInvoke.av_frame_free(&pDecodedFrame);
  
              FFmpegInvoke.av_free_packet(pPacket);
  
              GC.Collect();
  
          }
  
          nowFrameIndex = 0;
  
          return FrameBuffer.Count > 0 ? true : false;
  
      }