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• OpenCV video writing to named pipe

  21 janvier 2012, par user28667

  I'm trying to send videos created with OpenCV in real-time to user though Apache (user downloads video from a website). I don't need streaming video. I'm just trying to transfer whole video file. My OpenCV program writes video to a named pipe (created with mkfifo) and PHP scrpt reads from it and outputs to user.

  The problem is that pipe-transfered videos doesn't open in Windows. They're shorter exactly at 7072 bytes (checked with different videos). They are not just truncated. The first difference between videos appeared in 5-th byte. And there is no mistake in PHP script. I've checked it using :

  cat fifo.avi > output.avi

  The result was the same. How to make OpenCV write videos to pipes just as to normal files ? Why this happens ? Or is there another way to send videos in real-time to user ?

  P. S. Thanks and sorry for bad English
  P. P. S. I'm creating CvVideoWriter with this code if it matters :

  cvCreateVideoWriter("fifo.avi",CV_FOURCC('M','J','P','G'),25,cvSize(blah blah blah),1)

• hwcontext_vulkan : correctly download and upload flipped images

  21 avril 2020, par Lynne

  hwcontext_vulkan : correctly download and upload flipped images
  We derive the destination buffer stride from the input stride,
  
  which meant if the image was flipped with a negative stride,
  
  we'd be FFALIGNING a negative number which ends up being huge,
  
  thus making the Vulkan buffer allocation fail and the whole
  
  image transfer fail.
  Only found out about this as OpenGL compositors can copy an entire
  
  image with a single call if its flipped, rather than iterate over
  
  each line.
  

  • [DH] libavutil/hwcontext_vulkan.c

• 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.