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• Array Getting Lost While Passing From C++ to C Using Callback [duplicate]

  23 décembre 2020, par Abhishek Sharma

  I am trying to write Video Using FFmpeg by generating frame at run time using direct3d and the frames are generated using sharp dx at c# and I use window runtime to callback to c# to generate Frame And return Platform::Array of Byte ;

  


  so for writing video using FFmpeg, I used C code that writes video, and to ask for generating frame I implemented a callback to generate a frame and all that in StaticLib

  


  uint8_t*(*genrate_frame_callback)(int) = NULL;   


  


  now in C-File, I call fill_image to get the frame and write to the video

  


  static void fill_image(int frame_index, int width, int height)
{
    int x, y, i;

    i = frame_index;
    auto result = genrate_frame_callback(frame_index);// after passing this point while using debugger reults single element not even array
    .
    .
    .
    code to write video
    
}


  


  now when I call to Write Video before that pass this function to the callback that is in the c++ file in a Window Runtime Component that reference to static lib

  


  uint8_t* genrate_frame(int args)&#xA;{&#xA;    auto frame = FireGenrateFramet(args); // returns Platform::Array<byte>&#xA;    vector v(frame->begin(), frame->end());&#xA;    return v.data();// data is abilabe to this point &#xA;}&#xA;</byte>

  


  now the result variable contains a single element
I am new to c++ and c and unable to understand why is data not passed to the function using call back

  


  Edit :

  


  then can you help me with how to pass Data I tried using the global Scope Variable c++ file too but still,
it gets lost,
but after introducing another call back to read data stored in global Variable it read the whole data correctly

  


  vector frame_v;
uint8_t* genrate_frame(int args)
{
    auto frame = FireGenrateFrame(args);
     vector v(frame->begin(), frame->end());
    frame_v = v;
    return v.data();// this loose the Same 
}

uint8_t read_pixal(int args)
{
    return frame_v[args];// where as it read out correctly
}


  


  but I don't want to store and add new call back an read from their just pass the array

  


• A nice comparison of mics

  3 juin 2010

  DVEStore has done a great comparison of different types of microphones on video. Audio is a black art, and folks rarely put in the time to do A/B/C comparisons. We tend to just default to a set of mics that we’ve decided are "good enough" and then don’t go back to reevaluate.

• FFmpeg - Rotating at angle

  23 septembre 2017, par connor

  I’ve been working through FFmpeg, but I have been unable to get a rotation to run from the examples they have on their site. I am trying to "wiggle" a video back and forth at a fixed point on the bottom - think a head moving left to right (and so on).

  I am attempting to do this with the filter "rotate" (https://ffmpeg.org/ffmpeg-filters.html#rotate). Attempting to use their examples, I get an error.

  This is what I have so far :

  ffmpeg -i vid1.mp4 -i vid2.mov -loop 1 -i image.png -filter_complex "\
  
      [2:v]alphaextract, scale=240x160[mask];\
  
      [0:v] scale=240x160, rotate=A*sin(2*PI/T*t) [ascaled];\
  
      [ascaled][mask]alphamerge[masked];\
  
      [1:v]scale=480x360[background];\
  
      [background][masked]overlay=120:20"\
  
      -c:a copy 65B6354F61B4AF02_HD_sq.MOV

  I am using "rotate" directly from an example in an attempt to get something to run at all.

  The error I get back is :

  [Parsed_rotate_3 @ 0x7ff4476045e0] [Eval @ 0x7fff5b3e3f00] Undefined constant or missing '(' in 'T*t)'
  
  [Parsed_rotate_3 @ 0x7ff4476045e0] Error occurred parsing angle expression 'A*sin(2*PI/T*t)'
  
  [Parsed_rotate_3 @ 0x7ff4476045e0] Failed to configure output pad on Parsed_rotate_3
  
  Error reinitializing filters!
  
  Failed to inject frame into filter network: Invalid argument
  
  Error while processing the decoded data for stream #1:0

  If I remove ’A’, ’T’, ’sin’, etc, rotate does actually work, but far from the desired behavior.

  Am I missing something to expose those params ?