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• Feeding FFMPEG from buffer in c code RAW H264 to MP4 wrapping

  8 mai 2017, par abraxas1

  i have a raw h264 stream coming in from cameras with a custom API. data gets put into a callback function in my c code.

  i need to wrap this as mp4. i’m using ffmpeg to do this now, but only after the h264es file has been written and closed, so very time consuming on a beaglebone-like processor.

  i have been trying to write this data to a named pipe and feed that to ffmpeg but can not get this to work. maybe i’m not opening/closing pipes properly, it hangs. or not specifying the piping properly for ffmpeg.

  is it possible to feed the buffered data more directly to ffmpeg ?
  or, how do i set up the named pipe to work properly ?

  first i’m opening the fifo like this

  g_fifoname="/tmp/fifocam1.h264";
  
  mkfifo(g_fifoname, 0666);               // make the fifos
  
  fd_fifo[ch+brd*2] = open(g_fifoname, O_RDWR);

  then, i’m calling ffmpeg like this, at this moment anyway. trying many things.

  char* execargs[]={PATH_TO_FFMPEG,"-re","-y","-framerate","30","-f","h264","-video_size","1920x1080","-i",g_fifname,"-c:v","copy","-an",pathname, (char*)0};

  i probably got the ffmpeg call wrong. argh.
  i open the fifo first, then start ffmpeg.
  when streaming is stopped i close fifo’s, then close ffmpeg output file.

  ffmpeg is so powerful and frustrating to wrangle.
  thanks all,

• lavfi/drawbox : refine code

  14 mai 2021, par Ting Fu

  lavfi/drawbox : refine code
  Extract common code of filter_frame() and drawgrid_filter_frame() to draw_region().
  Signed-off-by : Ting Fu <ting.fu@intel.com>
  

  • [DH] libavfilter/vf_drawbox.c

• How to stream frames from OpenCV C++ code to Video4Linux or ffmpeg ?

  6 juillet 2022, par usamazf

  I am experimenting with OpenCV to process frames from a video stream. The goal is to fetch a frame from a stream, process it and then put the processed frame to a new / fresh stream.

  


  I have been able to successfully read streams using OpenCV video capture functionality. But do not know how I can create an output stream with the processed frames.

  


  In order to do some basic tests, I created a stream from a local video file using ffmpeg like so :

  


  ffmpeg -i sample.mp4 -v 0 -vcodec mpeg4 -f mpegts \
        "udp://@127.0.0.1:23000?overrun_nonfatal=1&fifo_size=50000000"


  


  And in my C++ code using the VideoCapture functionality of the OpenCV library, I am able to capture the above created stream. A basic layout of what I am trying to achieve is attached below :

  


  cv::VideoCapture capture("udp://@127.0.0.1:23000?overrun_nonfatal=1&fifo_size=50000000", cv::CAP_FFMPEG);

cv::Mat frame;

while (true) 
{
    // use the above stream to capture a frame
    capture >> frame;
    
    // process the frame (not relevant here)
    ...

    // finally, after all the processing is done I 
    // want to put this frame on a new stream say at
    // udp://@127.0.0.1:25000, I don't know how to do
    // this, ideally would like to use Video4Linux but
    // solutions with ffmpeg are appreciated as well
}


  


  As you can see from comment in above code, I don't have any idea how I should even begin handling this, I tried searching for similar questions but all I could find was how to do VideoCapture using streams, nothing related to outputting to a stream.

  


  I am relatively new to this and this might seem like a very basic question to many of you, please do excuse me.