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• Real-time streaming of rawdata images to Android with FFMPEG

  29 juillet 2015, par Philies

  CONDITIONS

  I have an C++ server (Linux) and want to transmit rawdata images (RGB, 32bit) to an Android device in real-time.
  The server generates the rawdata images (with or without bitmap header) continuously every x miliseconds. Now, I want to put the rawdata images into a stream and transmit them without much delay to the Android client.

  I’ve chosen FFMPEG for this kind of job.

  The input for FFMPEG should be the rawdata images, which are generated just in time. The output should be an rtsp stream (h264 or is another format better ?).
  On client side I will play the stream with the Android MediaPlayer. That works for a RTSP url like rtsp ://184.72.239.149/vod/mp4:BigBuckBunny_115k.mov

  ---

  PREVIOUS APPROCH :

  I’ve installed FFMPEG on my server.

  Depending on this question : https://ffmpeg.org/pipermail/ffmpeg-user/2013-April/014617.html ... here is my FFMEG command :

  ffmpeg -an -f rawvideo -vcodec rawvideo -pix_fmt rgb32 -r 10 -i -vcodec libx264 -r 30 -tune zerolatency -preset ultrafast -bsf:v h264_mp4toannexb -f mpegts udp://192.168.1.20:1234

  Explanation of the parameters :

  • -an = ignore audio
  • -report = log file in current directory

  INPUT :

  • -f = rawvideo (video format)
  • -vcodec = rawvideo (video codec)
  • -pix_fmt = rgb32
  • -r = 10 (frame rate)

  OUTPUT :

  • -vcodec = libx264
  • -r = 30 (frame rate)
  • -bsf:v = h264_mp4toannexb
  • -f = mpegts udp ://192.168.1.20:1234

  ---

  C++ Server Code Snippet :

  /* -------  Get image rawdata from source ------- */
  
  ...
  
  /* -------  Create image header which fits to the image rawdata ------- */
  
  ...
  
  
  
  /* ------- Store the picture local (not necessary?) ------- */
  
  FILE *f;
  
  f = fopen("/home/philies/test.bmp","wb");
  
  
  
  //Write Bitmap Headers
  
  fwrite(&imageFileHeader,1,sizeof(imageFileHeader),f);
  
  fwrite(imageInfoHeader,1, imageInfoHeader,f);
  
  
  
  //Write Bitmap Rawdata
  
  fwrite(lastImage.GetBitmapRawData(),1,imageSize,f);
  
  
  
  
  
  —> ffmpeg ???

  ---

  PROBLEMS/QUESTIONS :

  1. How can I specify the rawvideo of the ffmpeg command respectively how can I specify my bitmap rawdata (with or without header ?) as the input of the FFMPEG ?

  2. Is the FFMPEG command correct ?

  If I fire the FFMPEG command in the terminal I get this error :

  vcodec : no such file or directory

  EDIT :
  In the first step, I will open the udp stream with the VLC player on my Android device. After that I will set up a FFserver to create a RTSP stream

• ffmpeg timecode burn isn't correct with 29.97 video

  26 juin 2015, par Austin A.

  I have a 29.97fps video, and I’m trying to burn the timestamp onto the video in the middle of the frame. For debugging, I’m also putting the current frame number. Here’s my current ffmpeg pipeline :

  ffmpeg -i input.mkv -vf "drawtext=fontfile=FreeMono.ttf: 
  
     timecode='00\:00\:00\:00': timecode_rate=2997/100: x=960: y=540: 
  
     fontcolor=white: box=1: boxcolor=0x00000099,drawtext=fontfile=FreeMono.ttf:
  
     text='Frame %{n}': x=960: y=560: fontcolor=white: box=1:
  
     boxcolor=0x00000099" -c:v libx264 -crf 15 -preset fast -tune fastdecode 
  
     output.mkv

  It looks like the timestamps burned into the video aren’t quite right, because the playback timer in VLC slowly gets out of sync, about 4 seconds per hour.

  When the playback timer gets to 10 minutes, I expect the frame count to be at 29.97 * 10 * 60 = 17982, and indeed it is. But the timestamp is 9:59 + 11 frames. This makes me think the timecode_rate is being interpreted as 30fps, since after 10 minutes, the difference between 30fps and 29.97fps is the missing 18 frames.

  I’ve tried timecode_rate=2997/100, timecode_rate=30000/1001, timecode_rate=29.97, and they all give the same results. timecode_rate=60 does change the timestamp’s behavior, so I know ffmpeg is listening to this parameter. It just doesn’t seem to want to write 29.97fps timestamps.

  Any ideas ?

• x264enc plugin settings for VBV buffer

  11 juin 2015, par Dundar

  I am trying to implement VBV buffer in x264enc plugin in gstreamer. What I want to achieve is setting rc.i_vbv_max_bitrate to 10K and rc.i_vbv_buffer_size to 10K.
  However, what I see in the x264enc source code,

  encoder->x264param.rc.i_vbv_max_bitrate = encoder->bitrate;
  
  encoder->x264param.rc.i_vbv_buffer_size
  
        = encoder->x264param.rc.i_vbv_max_bitrate
  
        * encoder->vbv_buf_capacity / 1000;

  Here is my settings :

   g_object_set(G_OBJECT(_videoEncoder),
  
                   "tune",             (guint)4,
  
                   "speed-preset",     (guint)1,
  
                   "byte-stream",      (gboolean)TRUE,
  
                   "bitrate",          (guint) 10000,
  
                   "vbv-buf-capacity", (guint) 1000,
  
                   "intra-refresh",    (gboolean)TRUE,
  
                   NULL);

  Do you see anything wrong in this ? tune=4 means ultrafast, speed-preset=1 means zerolatency right ?

  Thanks.