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• AVFormatContext : interrupt callback proper usage ?

  17 juillet 2021, par Daniel

  AVFormatContext's interrupt_callback field is a

  


  


  Custom interrupt callbacks for the I/O layer.

  


  


  It's type is AVIOInterruptCB, and it explains in comment section :

  


  


  Callback for checking whether to abort blocking functions.

  


  AVERROR_EXIT is returned in this case by the interrupted function. During blocking operations, callback is called with opaque as parameter. If the callback returns 1, the blocking operation will be aborted.

  


  No members can be added to this struct without a major bump, if new elements have been added after this struct in AVFormatContext or AVIOContext.

  


  


  I have 2 questions :

  


  

  1. what does the last section means ? Especially "without a major bump" ?

  


  2. If I use this along with an RTSP source, when I close the input by avformat_close_input, the "TEARDOWN" message is being sent out, however it won't reach the RTSP server.

  


  


  For 2 : here is a quick pseudo-code for demo :

  


  int pkts = 0;
bool early_exit = false;

int InterruptCallback(void* ctx) {
    return early_exit ? 1 : 0;
}

void main() {
  ctx = avformat_alloc_context
  ctx->interrupt_callback.callback = InterruptCallback;

  avformat_open_input
  avformat_find_stream_info
  pkts=0;
  while(!early_exit) {
    av_read_frame

    if (pkts++ > 100) early_exit=true;
  }

  avformat_close_input
}


  


  In case I don't use the interrupt callback at all, TEARDOWN is being sent out, and it also reaches the RTSP server so it can actually tear down the connection. Otherwise, it won't tear down it, and I have to wait until TCP socket times out.

  


  What is the proper way of using this interrupt callback ?

  


• how to put EXEC command in loop in TCL with windows platform

  26 février 2019, par M. D. P

  how to put EXEC command in loop in TCL with windows platform.

  I need to run EXEC command continuously. but the problem after its first execution it stops.

  my code is

  proc a {} {
  
    set a 1
  
    for {set i 0} {$i < 10} {incr i} {
  
      puts "I inside first loop: $i"
  
      exec ffmpeg -f dshow -benchmark -i "video=Integrated Webcam" \
  
              -s 1280x720 c:/test/sample_image.avi
  
    }
  
  }
  
  a

  The above program should capture 10 video. but it captures only one video and comes out from the loop and stops the execution.

  can any of my friend help me by providing me the answer with the required modification in code.

• ffmpeg make image and movie in one command

  22 juin 2012, par knishua

  this is the situation :
  given a thumbnail, i need to overlay it on top of an image.

  so, i need to scale image pass it as parameter to overlay pass that to drawtext.

  I have got so far, adding multiple text + overlay + thumbnail,

  1. ffmpeg -threads 8 -i D:/imagesequence/background.jpg -vf "movie='D\:/imagesequence/dpx/thumbnail.jpg' [watermark]; [in][watermark] overlay=(main_w-overlay_w)/2:(main_h-overlay_h)/3[water];[water] drawtext=fontsize=32:fontcolor=White:fontfile=/Windows/Fonts/arial.ttf:text='shotName':x=(w)/2:y=(h)-50,drawtext=fontsize=28:fontcolor=White:fontfile=/Windows/Fonts/arial.ttf:text='Notes \:':x=(w)/5:y=(h)-90,drawtext=fontsize=28:fontcolor=White:fontfile=/Windows/Fonts/arial.ttf:text='Frame Range \:':x=(w)/5:y=(h)-130,drawtext=fontsize=28:fontcolor=White:fontfile=/Windows/Fonts/arial.ttf:text='Lens \:':x=(w)/5:y=(h)-170,drawtext=fontsize=28:fontcolor=White:fontfile=/Windows/Fonts/arial.ttf:text='Undistortion \:':x=(w)/5:y=(h)-210,drawtext=fontsize=28:fontcolor=White:fontfile=/Windows/Fonts/arial.ttf:text='Image Sequence \:':x=(w)/5:y=(h)-250,drawtext=fontsize=28:fontcolor=White:fontfile=/Windows/Fonts/arial.ttf:text='Date \:':x=(w)/5:y=(h)-290,drawtext=fontsize=28:fontcolor=White:fontfile=/Windows/Fonts/arial.ttf:text='Element Name \:':x=(w)/5:y=(h)-330,drawtext=fontfile=/Windows/Fonts/arial.ttf:text='FUTUREWORKS':x=130:y=200:fontsize=54:fontcolor=White[out]" D:\imagesequence\dpx\brn_055.0000.dpx

  2. ffmpeg -threads 8 -i D:\imagesequence\dpx\brn_055.%04d.dpx -vf "drawtext=fontfile=/Windows/Fonts/arial.ttf:text='shotcam':x=(w)/2:y=(h)-35:fontsize=24:fontcolor=Yellow,drawtext=fontfile=/Windows/Fonts/arial.ttf:text='Frame \:':x=(w)-600:y=(h)-35:fontsize=24:fontcolor=Yellow,drawtext=fontfile=/Windows/Fonts/arial.ttf:text='Focal Length \:':x=(w)-600:y=(h)-65:fontsize=24:fontcolor=Yellow" D:\imagesequence\dpx\test2.mov

  3. how do i scale an image and pass it to movie, in 1

  4. how do i make a blackscreen size that of an image say
     'D :\imagesequence\dpx\brn_055.0001.dpx' and pass it to input in 1

  5. is it possible do bother 1 and 2 in one command line ( ffmpeg ....)
     i.e. make an image from first point ( 1 ) and continue with making .mov ( of 1 image + input from point 2 )

  or in other words if it is not possible to do (1 + 2) in one command then is it possible to first execute 1 then execute 2 ( but with output from 1)
  do it