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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

• Merge two .m4a files or convert .wav file to m4a

  8 novembre 2011, par Pannu

  I was looking for a way to record in mpeg-4 with the ability to pause and resume but it seemed like there isn't one. So I decided to record in raw wave format and convert to .m4a. Is there a way I can convert .wav file to .m4a in android. I've looked around for mencoder port for android but found none, there were some post's about porting ffmpeg to android on linux but its not quite clear how i can use it in android to merge two .m4a files or convert .wav file to .m4a.

• Input seeking for frame at specified timestamp with Py-AV

  9 décembre 2019, par neonScarecrow

  I have a project already using Py-AV and am trying to replicate a specific ffmpeg command. The goal is to get a frame roughly around the specified timestamp.

  Here’s the ffmpeg commmand :
  https://trac.ffmpeg.org/wiki/Seeking

  ffmpeg -ss 14 -i https://some_url.mp4 -frames:v 1 frame_at_14_seconds.jpg

  Here’s my code :

      #return one frame around 14 seconds into the movie
  
      target_sec = 14 
  
      container = av.open('https://some_url.mp4', 'r')
  
      container.streams.video[0].thread_type = 'AUTO'
  
      video_stream = next(s for s in container.streams if s.type == 'video')
  
      time_base = float(video_stream.time_base)
  
      target_timestamp = int(target_sec / time_base) + video_stream.start_time
  
      video_stream.seek(target_timestamp)
  
      for frame in container.decode(video_stream):
  
          frame.to_image().save('frame_at_14_seconds.jpg')
  
          break

  Additionally, I have found any documentation about this, but does anyone know if either command (ffmpeg/av.open) is downloading the entire file to a tmp file behind the scenes. I’m looking for a less memory-intensive way to read a frame for every second in an up to 60 second video.