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• ffmpeg : create a video of 10 seconds before and 10 seconds after the occurrence of a certain event [closed]

  28 août 2023, par pozzugno

  From a video stream (RTSP) transmitted from an IPCam, I'd like to generate a short video starting from 10 seconds before an event and total duration 20 seconds, so the event is in the middle of the video.

  


  The event is an alarm triggered by an external device. I'd like to see what happened immediately before and after this alarm.

  


  Because I need the video before the event (and I don't know when the event will occur), I am forced to receive the stream continuously. The idea is to use segment mux, so I'm testing the following command :

  


  ffmpeg -hide_banner -rtsp_transport tcp -stimeout 10000000 -i rtsp://... -f segment -segment_time 2 -reset_timestamps 1 -segment_wrap 12 -ccopy -map 0:v /var/ramdisk/C1/%d.mp4


  


  In the output folder I will have 12 files : 0.mp4, 1.mp4,... 11.mp4. Each file is a video of duration 2 seconds.

  


  When my Linux service (always running) detects the alarm from the external device, it waits for 10 seconds and launch a new ffmpeg command that concatenate the short video files in one bigger video file. However I'm in trouble with the right command line to do what I need.

  


• Loading and unloading ffmpeg jni library based on when it's needed

  30 septembre 2014, par Alin

  I finally managed to compile ffmpeg for android and I’ve been able to use it in my app.

  Here is the scenario of my app :

  • I show the user a gridview with thumbnails of images and videos
  • the user can click on a cell and it is taken to image/video details where he can see the full image or play the video
  • the user can apply an image over an video and this is when ffmpeg is used

  So basically, the user might never actually use the watermarking option or he can do it very rare because the amount of available videos is way smaller than images.

  I am loading the ffmpeg library, first time it is needed by running :

  static {
  
       System.loadLibrary("ffmpeglib");
  
  }

  Now here are my questions :

  1. loading the library like this, uses app’s memory and resources ?
  2. can I unload the library, or better said, is it needed to unload it ? I have not found any java code like System.unloadLibrary to take care of unloading
  3. Since the library might be used rarely, wouldn’t a load => do encoding => unload be a better approach ? Or maybe having it loaded would allow easy reuse since no loading is necessary.
  4. If I use an IntentService to load the library and make the encoding, when the service completes the job, does the library gets unloaded ?

• TCP or UDP ? Delays building up on production for video stream

  31 janvier 2020, par Ben Beri

  I am creating a video stream from a camera with FFMPEG and nodejs stream Duplex class.

  this.ffmpegProcess = spawn('"ffmpeg"', [
  
  
  
    '-i', '-',
  
    '-loglevel', 'info',
  
  
  
    /**
  
     * MJPEG Stream
  
     */
  
  
  
    '-map', '0:v',
  
    '-c:v', 'mjpeg',
  
    '-thread_type', 'frame', // suggested for performance on StackOverflow.
  
    '-q:v', '20', // force quality of image. 2-31 when 2=best, 31=worst
  
    '-r', '25', // force framerate
  
    '-f', 'mjpeg',
  
    `-`,
  
  
  
  ], {
  
    shell: true,
  
    detached: false,
  
  });

  On local network, we are testing it with a few computers and every thing works very stable with latency of maximum 2 seconds.

  However, we have imported the service to AWS production, when we connect the first computer we have a latency of around 2 seconds, but if another client connects to the stream, they both start delaying a lot, where the latency builds up to 10+ seconds, and in addition the video is very slow, as in the motion between frames.

  Now I asked about TCP or UDP is because we are using TCP for the stream, which means that every packet that is sent is implementing the TCP syn-ack-synack protocol and sequence.

  My question is, could TCP really be causing such an issue that the delays get up to 10 seconds with very slow motion ? because on local network it works very just fine.