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• Saving scatterplot animations with matplotlib produces blank video file

  1er avril 2013, par user2175850

  I am having a very similar problem to this question

  but the suggested solution doesn't work for me.

  I have set up an animated scatter plot using the matplotlib animation module. This works fine when it is displaying live. I would like to save it to an avi file or something similar. The code I have written to do this does not error out but the video it produces just shows a blank set of axes or a black screen. I've done several checks and the data is being run and figure updated it's just not getting saved to video...

  I tried removing "animated=True" and "blit=True" as suggested in this question but that did not fix the problem.

  I have placed the relevant code below but can provide more if necessary. Could anyone suggest what I should do to get this working ?

  def initAnimation(self):
  
          rs, cfgs = next(self.jumpingDataStreamIterator)     
  
          #self.scat = self.axAnimation.scatter(rs[0], rs[1], c=cfgs[0], marker='o')
  
          self.scat = self.axAnimation.scatter(rs[0], rs[1], c=cfgs[0], marker='o', animated=True)
  
          return self.scat,
  
  
  
  
  
  def updateAnimation(self, i):
  
      """Update the scatter plot."""
  
      rs, cfgs = next(self.jumpingDataStreamIterator)
  
      # Set x and y data...
  
      self.scat.set_offsets(rs[:2,].transpose()) 
  
      #self.scat = self.axAnimation.scatter(rs[0], rs[1], c=cfgs[0], animated=True)
  
      # Set sizes...
  
      #self.scat._sizes = 300 * abs(data[2])**1.5 + 100
  
      # Set colors..
  
      #self.scat.set_array(cfgs[0])
  
      # We need to return the updated artist for FuncAnimation to draw..
  
      # Note that it expects a sequence of artists, thus the trailing comma.
  
      matplotlib.pyplot.draw()
  
      return self.scat,
  
  
  
  def animate2d(self, steps=None, showEvery=50, size = 25):
  
      self.figAnimation, self.axAnimation = matplotlib.pyplot.subplots()
  
      self.axAnimation.set_aspect("equal")
  
      self.axAnimation.axis([-size, size, -size, size])
  
      self.jumpingDataStreamIterator = self.jumpingDataStream(showEvery)
  
  
  
      self.univeseAnimation = matplotlib.animation.FuncAnimation(self.figAnimation, 
  
                              self.updateAnimation, init_func=self.initAnimation,
  
                              blit=True)
  
      matplotlib.pyplot.show()
  
  
  
  def animate2dVideo(self,fileName=None, steps=10000, showEvery=50, size=25):
  
      self.figAnimation, self.axAnimation = matplotlib.pyplot.subplots()
  
      self.axAnimation.set_aspect("equal")
  
      self.axAnimation.axis([-size, size, -size, size])
  
      self.Writer = matplotlib.animation.writers['ffmpeg']
  
      self.writer = self.Writer(fps=1, metadata=dict(artist='Universe Simulation'))
  
      self.jumpingDataStreamIterator = self.jumpingDataStream(showEvery)
  
  
  
      self.universeAnimation = matplotlib.animation.FuncAnimation(self.figAnimation, 
  
                              self.updateAnimation, scipy.arange(1, 25), init_func=self.initAnimation)
  
  
  
      self.universeAnimation.save('C:/universeAnimation.mp4', writer = self.writer)

• using node-fluent-ffmpeg to transcode with ffmpeg on windows not working

  25 juillet 2015, par jansmolders86

  I’m trying to use the module node-fluent-ffmpeg (https://github.com/schaermu/node-fluent-ffmpeg) to transcode and stream a videofile. Since I’m on a Windows machine, I first downloaded FFMpeg from the official site (http://ffmpeg.zeranoe.com/builds/). Then I extracted the files in the folder C :/FFmpeg and added the path to the system path (to the bin folder to be precise). I checked if FFmpeg worked by typing in the command prompt : ffmpeg -version. And it gave a successful response.

  After that I went ahead and copied/altered the following code from the module (https://github.com/schaermu/node-fluent-ffmpeg/blob/master/examples/express-stream.js) :

  app.get('/video/:filename', function(req, res) {
  
  res.contentType('avi');
  
  console.log('Setting up stream')
  
  
  
  var stream = 'c:/temp/' + req.params.filename
  
  var proc = new ffmpeg({ source: configfileResults.moviepath + req.params.filename, nolog: true, timeout: 120, })
  
      .usingPreset('divx')
  
      .withAspect('4:3')
  
      .withSize('640x480')
  
      .writeToStream(res, function(retcode, error){
  
          if (!error){
  
              console.log('file has been converted succesfully',retcode);
  
          }else{
  
              console.log('file conversion error',error);
  
          }
  
      });
  
  });

  I’ve properly setup the client with flowplayer and tried to get it running but
  nothing happens. I checked the console and it said :

  file conversion error timeout

  After that I increased the timeout but somehow, It only starts when I reload the page. But of course immediately stops because of the page reload. Do I need to make a separate node server just for the transcoding of files ? Or is there some sort of event I need to trigger ?

  I’m probably missing something simple but I can’t seem to get it to work.
  Hopefully someone can point out what I’ve missed.

  Thanks

• Error using FFMPEG to convert each input image into H264 compiling in Visual Studio running in MevisLab

  21 février 2014, par user3012914

  I am creating a ML Module in MevisLab Framework, I am using FFMPEG to convert each image i get into a H264 Video and save it after I get all the frames. But unfortunately I have problem allocating the output buffer size. The application crashes when I include this in my code.If I am not including it, the output file size is just 4kb. Nothing is stored in it.

  I am also not very sure whether it is correct way of getting the HBitmap into the Encoder. Would be great to have your suggestions.

  My Code :

  BITMAPINFO bitmapInfo;
  
              HDC        hdc;
  
  
  
              ZeroMemory(&bitmapInfo, sizeof(bitmapInfo));
  
  
  
              BITMAPINFOHEADER &bitmapInfoHeader = bitmapInfo.bmiHeader;
  
              bitmapInfoHeader.biSize            = sizeof(bitmapInfoHeader);
  
              bitmapInfoHeader.biWidth           = _imgWidth;
  
              bitmapInfoHeader.biHeight          = _imgHeight;
  
              bitmapInfoHeader.biPlanes          =  1;
  
              bitmapInfoHeader.biBitCount        = 24;
  
              bitmapInfoHeader.biCompression     = BI_RGB;
  
              bitmapInfoHeader.biSizeImage       = ((bitmapInfoHeader.biWidth * bitmapInfoHeader.biBitCount / 8 + 3) & 0xFFFFFFFC) * bitmapInfoHeader.biHeight;
  
              bitmapInfoHeader.biXPelsPerMeter   = 10000;
  
              bitmapInfoHeader.biYPelsPerMeter   = 10000;
  
              bitmapInfoHeader.biClrUsed         = 0;
  
              bitmapInfoHeader.biClrImportant    = 0;
  
              //RGBQUAD* Ref = new RGBQUAD[_imgWidth,_imgHeight];
  
              HDC hdcscreen = GetDC(0);
  
  
  
              hdc = CreateCompatibleDC(hdcscreen);
  
              ReleaseDC(0, hdcscreen);
  
  
  
              _hbitmap = CreateDIBSection(hdc, (BITMAPINFO*) &bitmapInfoHeader, DIB_RGB_COLORS, &_bits, NULL, NULL);

  To get the BitMap I use the above code. Then I allocate the Codec Context as followed

  c->bit_rate = 400000;
  
                  // resolution must be a multiple of two 
  
                  c->width = 1920;
  
                  c->height = 1080;
  
                  // frames per second 
  
                  frame_rate = _framesPerSecondFld->getIntValue();
  
                  //AVRational rational = {1,10};
  
                  //c->time_base = (AVRational){1,25};
  
                   //c->time_base = (AVRational){1,25};
  
                   c->gop_size = 10; // emit one intra frame every ten frames 
  
                   c->max_b_frames = 1;
  
                   c->keyint_min = 1;   //minimum GOP size
  
                   c->time_base.num = 1;                                  // framerate numerator
  
                   c->time_base.den = _framesPerSecondFld->getIntValue(); 
  
                   c->i_quant_factor = (float)0.71;                        // qscale factor between P and I frames
  
                   c->pix_fmt = AV_PIX_FMT_RGB32;
  
                   std::string msg;
  
                   msg.append("Context is stored");
  
                   _messageFld->setStringValue(msg.c_str());

  I create the Bitmap Image as followed from the input

  PagedImage *inImg = getUpdatedInputImage(0);
  
          ML_CHECK(inImg);
  
          ImageVector imgExt = inImg->getImageExtent();
  
          if ((imgExt.x = _imgWidth) && (imgExt.y == _imgHeight))
  
          {
  
          if (((imgExt.x % 4)==0) && ((imgExt.y % 4) == 0))
  
          {
  
                   // read out input image and write output image into video
  
                  // get input image as an array
  
                  void* imgData = NULL;
  
                  SubImageBox imageBox(imgExt); // get the whole image
  
                  getTile(inImg, imageBox, MLuint8Type, &imgData);
  
                  iData = (MLuint8*)imgData;
  
                  int r = 0; int g = 0;int  b = 0;
  
                  // since we have only images with
  
                  // a z-ext of 1, we can compute the c stride as follows
  
                  int cStride = _imgWidth * _imgHeight;
  
                  uint8_t offset  = 0;
  
                  // pointer into the bitmap that is
  
                  // used to write images into the avi
  
                  UCHAR* dst = (UCHAR*)_bits;
  
                  for (int y = _imgHeight-1; y >= 0; y--)
  
                  { // reversely scan the image. if y-rows of DIB are set in normal order, no compression will be available.
  
                      offset = _imgWidth * y;
  
                      for (int x = 0; x < _imgWidth; x++)
  
                      {
  
                          if (_isGreyValueImage)
  
                          {
  
                              r = iData[offset + x];
  
                              *dst++ = (UCHAR)r;
  
                              *dst++ = (UCHAR)r;
  
                              *dst++ = (UCHAR)r;
  
                          } 
  
                          else
  
                          {
  
                              b = iData[offset + x]; // windows bitmap need reverse order: bgr instead of rgb
  
                              g = iData[offset + x + cStride          ];
  
                              r = iData[offset + x + cStride + cStride];
  
  
  
                              *dst++ = (UCHAR)r;
  
                              *dst++ = (UCHAR)g;
  
                              *dst++ = (UCHAR)b;
  
                          }
  
                          // alpha channel in input image is ignored
  
                      }
  
                  }

  Then I add it to the Encoder as followed as write as H264

   in_width   = c->width;
  
                   in_height  = c->height;
  
                   out_width  = c->width;
  
                   out_height = c->height;
  
                   ibytes = avpicture_get_size(PIX_FMT_BGR32, in_width, in_height);
  
                   obytes = avpicture_get_size(PIX_FMT_YUV420P, out_width, out_height);
  
                   outbuf_size = 100000 + c->width*c->height*(32>>3);      // allocate output buffer
  
                   outbuf = static_cast(malloc(outbuf_size));
  
  
  
                   if(!obytes)
  
                   {
  
                       std::string msg;
  
                       msg.append("Bytes cannot be allocated");
  
                       _messageFld->setStringValue(msg.c_str());
  
                   }
  
                   else
  
                   {
  
                       std::string msg;
  
                       msg.append("Bytes allocation done");
  
                       _messageFld->setStringValue(msg.c_str());
  
                   }
  
                   //create buffer for the output image
  
                   inbuffer  =  (uint8_t*)av_malloc(ibytes);
  
                   outbuffer =  (uint8_t*)av_malloc(obytes);
  
                   inbuffer  =  (uint8_t*)dst;
  
  
  
                   //create ffmpeg frame structures.  These do not allocate space for image data, 
  
                   //just the pointers and other information about the image.
  
                   AVFrame* inpic = avcodec_alloc_frame();
  
                   AVFrame* outpic = avcodec_alloc_frame();
  
  
  
                   //this will set the pointers in the frame structures to the right points in 
  
                   //the input and output buffers.
  
                   avpicture_fill((AVPicture*)inpic, inbuffer, PIX_FMT_BGR32, in_width, in_height);
  
                   avpicture_fill((AVPicture*)outpic, outbuffer, PIX_FMT_YUV420P, out_width, out_height);
  
                   av_image_alloc(outpic->data, outpic->linesize, c->width, c->height, c->pix_fmt, 1); 
  
                   inpic->data[0] += inpic->linesize[0]*(_imgHeight-1);                                                      // flipping frame
  
                   inpic->linesize[0] = -inpic->linesize[0];    
  
  
  
                   if(!inpic)
  
                   {
  
                       std::string msg;
  
                       msg.append("Image is empty");
  
                       _messageFld->setStringValue(msg.c_str());
  
                   }
  
                   else
  
                   {
  
                       std::string msg;
  
                       msg.append("Picture has allocations");
  
                       _messageFld->setStringValue(msg.c_str());
  
                   }
  
  
  
                   //create the conversion context
  
                   fooContext = sws_getContext(in_width, in_height, PIX_FMT_BGR32, out_width, out_height, PIX_FMT_YUV420P, SWS_FAST_BILINEAR, NULL, NULL, NULL);
  
                   //perform the conversion
  
                   sws_scale(fooContext, inpic->data, inpic->linesize, 0, in_height, outpic->data, outpic->linesize);
  
                   //out_size = avcodec_encode_video(c, outbuf,outbuf_size, outpic);
  
                   if(!out_size)
  
                   {
  
                       std::string msg;
  
                       msg.append("Outsize is not valid");
  
                       _messageFld->setStringValue(msg.c_str());
  
                   } 
  
                   else
  
                   {
  
                       std::string msg;
  
                       msg.append("Outsize is valid");
  
                       _messageFld->setStringValue(msg.c_str());
  
                   }
  
                       fwrite(outbuf, 1, out_size, f);
  
                       if(!fwrite)
  
                   {
  
                       std::string msg;
  
                       msg.append("Frames couldnt be written");
  
                       _messageFld->setStringValue(msg.c_str());
  
                   } 
  
                   else
  
                   {
  
                       std::string msg;
  
                       msg.append("Frames written to the file");
  
                       _messageFld->setStringValue(msg.c_str());
  
                   }
  
                      // for (;out_size; i++)
  
                      // {
  
                            out_size = avcodec_encode_video(c, outbuf, outbuf_size, NULL); 
  
                            std::string msg;                       
  
                            msg.append("Writing Frames");
  
                            _messageFld->setStringValue(msg.c_str());// encode the delayed frames
  
                            _numFramesFld->setIntValue(_numFramesFld->getIntValue()+1);
  
                            fwrite(outbuf, 1, out_size, f);
  
                      // }
  
                       outbuf[0] = 0x00;
  
                       outbuf[1] = 0x00;                                                                                               // add sequence end code to have a real mpeg file
  
                       outbuf[2] = 0x01;
  
                       outbuf[3] = 0xb7;
  
                       fwrite(outbuf, 1, 4, f);
  
  }

  Then close and clean the Image Buffer and file

    ML_TRACE_IN("MovieCreator::_endRecording()")
  
  if (_numFramesFld->getIntValue() == 0)
  
  {
  
      _messageFld->setStringValue("Empty movie, nothing saved.");
  
  } 
  
  else 
  
  {
  
      _messageFld->setStringValue("Movie written to disk.");
  
      _numFramesFld->setIntValue(0);
  
  if (_hbitmap)
  
  { 
  
      DeleteObject(_hbitmap); 
  
  }
  
  if (c != NULL)
  
  {
  
         av_free(outbuffer);     
  
         av_free(inpic);
  
         av_free(outpic);
  
         fclose(f);
  
         avcodec_close(c);                                                                                               // freeing memory
  
         free(outbuf);
  
         av_free(c);
  
  }
  
  }

  }

  I think the Main Problem is over here !!

                       //out_size = avcodec_encode_video(c, outbuf,outbuf_size, outpic);