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• Load PNG from disk into AVFrame

  15 février 2018, par Pedro Pereira

  I can’t seem to get this to work. This is what I got so far :

  // Variables
  
  int retOp; // for holding the operations results
  
  
  
  // Initializes FFmpeg
  
  av_register_all();
  
  
  
  // Open image
  
  uint8_t *buffer = NULL;
  
  size_t buffer_size;
  
  retOp = av_file_map("in.png", &buffer, &buffer_size, 0, NULL);
  
  if(retOp < 0){
  
      cerr << "Could not load image!" << endl;
  
      system("pause");
  
      return -1;
  
  }
  
  
  
  // Initialize AVFrame
  
  AVFrame* frame = av_frame_alloc();
  
  frame->width = 1920;
  
  frame->height = 1080;
  
  frame->format = AV_PIX_FMT_RGBA;

  The examples in the FFmpeg Doxygen don’t really help and there’s no support on the web. If there is let me know.

  Uncompressed RGBA image.

• How can I read all the data from a pipe and prevent it from closing ?

  23 septembre 2014, par slhck

  I’m trying to read raw YUV data from a compressed file using ffmpeg and pipes with Python.
  The ffmpeg command correctly spits out frames as raw YUV data, and I’m reading it like this :

  def read_from_pipe(pipe, amount):
  
      raw = pipe.stdout.read(amount)
  
      pipe.stdout.flush()
  
      return raw
  
  
  
  pipe_ref = subprocess.Popen('ffmpeg -i "' + input + '" -r 30 -c:v rawvideo -pix_fmt yuv420p -an -f rawvideo -t 5 -', 
  
    shell = True, 
  
    stdout = subprocess.PIPE, 
  
    bufsize=1920*1080*3*2)
  
  
  
  frame_num = 0
  
  while True:
  
      data = read_from_pipe(pipe_ref, width*height*3)
  
  
  
      # no more data
  
      if (len(data) != width*height*3))
  
          return results
  
  
  
      image = extract_image_data(data, width, height)
  
      # do something with image, put it into "results" and print frame / SSIM values to console
  
      frame_num += 1

  The problem is, as soon as ffmpeg is done converting all frames, my program stops. Since the program is a little slower than ffmpeg, it will stop receiving data and exit.

  Basically, for example, I can only work up to frame 30, then ffmpeg finishes at frame 60, and my program also exits. The command line output would say :

  Frame=25 SSIM=0.990472732391
  
  Frame=26 SSIM=0.98359411819
  
  Frame=27 SSIM=0.981074433586
  
  Frame=28 SSIM=0.97850843075
  
  frame=   60 fps= 27 q=0.0 Lsize=  182250kB time=00:00:02.00 bitrate=746496.0kbits/s dup=12 drop=0    
  
  video:182250kB audio:0kB subtitle:0 data:0 global headers:0kB muxing overhead 0.000000%
  
  Frame=29 SSIM=0.977698849804
  
  frame=   60 fps= 27 q=0.0 Lsize=  182250kB time=00:00:02.00 bitrate=746496.0kbits/s dup=12 drop=0    
  
  video:182250kB audio:0kB subtitle:0 data:0 global headers:0kB muxing overhead 0.000000%

  How can I get it to work on all frames that are output by ffmpeg ? Or is there any other easier way of obtaining the raw YUV data from any file if not through a pipe ? (I need it to work concurrently)

• how to add duration to mjpeg or how to make mjpeg faster

  10 octobre 2014, par n2v2rda2

  i have ip-cam mjpeg that i made and it have total 240 frames

  encode souce is
  ffmpeg.exe -framerate 25 -i c :\%06d.jpg\ -s 1920x1080 -qscale 1 -vcodec mjpeg -r 25 C :\result.mjpg -y

  now i want to play result.mjpg by mjpeg player i made

  my problem
  
  1. i can't get mjpeg's play time or duration time
  
  
  
  2. playing is slower then other movie player so i want to sync it and play more faster

  below is ffprobe result

  Input #0, mjpeg, from 'result.mjpg':
  
  Duration: N/A, bitrate: N/A
  
  Stream #0:0: Video: mjpeg, yuvj444p(pc, bt470bg), 1920x1080, 25 tbr, 1200k tbn, 25 tbc

  below is result added -show_frame

  [FRAME]
  
  media_type=video
  
  key_frame=1
  
  pkt_pts=720000
  
  pkt_pts_time=0.600000
  
  pkt_dts=720000
  
  pkt_dts_time=0.600000
  
  best_effort_timestamp=720000
  
  best_effort_timestamp_time=0.600000
  
  pkt_duration=48000
  
  pkt_duration_time=0.040000
  
  pkt_pos=4731406
  
  pkt_size=313289
  
  width=1920
  
  height=1080
  
  pix_fmt=yuvj444p
  
  sample_aspect_ratio=333:320
  
  pict_type=I
  
  coded_picture_number=0
  
  display_picture_number=0
  
  interlaced_frame=0
  
  top_field_first=0
  
  repeat_pict=0
  
  [/FRAME]

  ffprobe show me there are Duration : N/A, bitrate : N/A

  how do i set Duration and bitrate
  is there any encode-option i have to set ?

  when i decode mjpeg like below

  i can’t get duration just 0

  AVFormatContext*  pFC;
  
  int               ret;
  
  
  
  pFC = avformat_alloc_context();
  
  
  
  ret  = avformat_open_input(&pFC, filename, NULL, NULL);
  
  if (ret < 0) {
  
      // fail .
  
  }
  
  
  
  ret  = avformat_find_stream_info(pFC, NULL);
  
  if (ret < 0) {
  
      // fail
  
  }
  
  printf("duration %ld", pFC->duration);   <----- only 0