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• Serve a single frame of a video to a user as an image (efficiently)

  23 juillet 2014, par JoeRocc

  Problem :

  I have multiple 60 minute videos on my server (shared hosting). I need to serve a single frame of any one of these videos to a user instantly and efficiently. Expected maximum load is about 100 requests per minute.

  Notes :

  • I am on a shared hosting service, so FFmpeg is not a possibility (is FFmpeg efficient enough for 100 requests per minute anyway ?).
  • I don’t want to store hundreds of thousands of images on my server (my inodes are limited).

  Possible Solutions :

  • Load the video onto the client-side and then extract a frame and paint it to a canvas as per this article. Though I don’t want the user to have to download the whole video just to get a frame (will they have to do this ?).
  • Use some efficient server-side library to efficiently extract a frame and then serve it to the user.
  •  ???

• How to recover video from H264 frames and timestamps [closed]

  10 juin 2024, par kokosda

  My service receives H264 frames and some metadata related to them like Timestamp from MS Teams.

  


  Observations :

  


  

  • Those frames are inter-frame compressed.

  


  • Resolution of those frames can change.

  


  • Timestamps are like this one 39264692280552704. That represents year 125 if fed to .NET consturctor new DateTime(39264692280552704), so I need to add 1899 years to get a real date.

  


  • I can wrap the sequence to a playable mp4 container with ffmpeg -i input.h264 -c copy output.mp4, however it is not what I want because the resulting video plays too fast, like on fast forward. Thus, I would like those timestamps would be considered to recover a real timeline.

  


  


  I merged all the H264 frames in one file like input.h264 and saved all the timestamps in another file like metadata.json. In metadata.json, each object describes a single frame from input.h264.

  


  My question is how to recover the source video from frames and timestamps that I received from Teams ? Particularly, using FFMPEG.

  


• FFMPEG Command in Android Failing to Execute

  12 septembre 2020, par Zoe

  I'm trying to execute ffmpeg commands through an android app I'm developing.

  



  I found this post which has been somewhat useful :
Problems with ffmpeg command line on android

  



  and I downloaded a static build of ffmpeg from here : http://ffmpeg.gusari.org/static/

  



  The problem is, when this code runs

  



  public void merge_video(){


      String[] ffmpegCommand = new String[5];
      ffmpegCommand[0] = "/data/data/com.example.zovideo/ffmpeg";
      ffmpegCommand[1] = "-i";
      ffmpegCommand[2] = "concat:storage/emulated/0/DCIM/Camera/VID30141106_211509.mp4|storage/emulated/0/DCIM/Camera/VID30141106_211509.mp4";
      ffmpegCommand[3] = "copy";
      ffmpegCommand[4] = "storage/emulated/0/DCIM/ZoVideo/Output.mp4";  

      try {
          Process ffmpegProcess = new ProcessBuilder(ffmpegCommand).redirectErrorStream(true).start();

          String line;
          BufferedReader reader = new BufferedReader(new InputStreamReader(ffmpegProcess.getInputStream()));
          Log.d(null, "*******Starting FFMPEG");

          while((line = reader.readLine())!=null){

              Log.d(null, "***"+line+"***"); 
          }
          Log.d(null,"****ending FFMPEG****");

    } catch (IOException e) {
        e.printStackTrace();
    }
  }


  



  It fails when trying to start the process with

  



  Java.io.IOException: Error running exec(). Command: [/data/data/com.example.zovideo/ffmpeg, -i, concat:storage/emulated/0/DCIM/Camera/VID30141106_211509.mp4|storage/emulated/0/DCIM/Camera/VID30141106_211509.mp4, copy, storage/emulated/0/DCIM/ZoVideo/Output.mp4] Working Directory: null Environment: [ANDROID_ROOT=/system, EMULATED_STORAGE_SOURCE=/mnt/shell/emulated, LOOP_MOUNTPOINT=/mnt/obb, LD_PRELOAD=libsigchain.so, ANDROID_BOOTLOGO=1, EMULATED_STORAGE_TARGET=/storage/emulated, EXTERNAL_STORAGE=/storage/emulated/legacy, SYSTEMSERVERCLASSPATH=/system/framework/services.jar:/system/framework/ethernet-service.jar:/system/framework/wifi-service.jar, ANDROID_SOCKET_zygote=10, PATH=/sbin:/vendor/bin:/system/sbin:/system/bin:/system/xbin, ANDROID_DATA=/data, ANDROID_ASSETS=/system/app, ASEC_MOUNTPOINT=/mnt/asec, BOOTCLASSPATH=/system/framework/core-libart.jar:/system/framework/conscrypt.jar:/system/framework/okhttp.jar:/system/framework/core-junit.jar:/system/framework/bouncycastle.jar:/system/framework/ext.jar:/system/framework/framework.jar:/system/framework/telephony-common.jar:/system/framework/voip-common.jar:/system/framework/ims-common.jar:/system/framework/mms-common.jar:/system/framework/android.policy.jar:/system/framework/apache-xml.jar, ANDROID_PROPERTY_WORKSPACE=9,0, ANDROID_STORAGE=/storage]


  



  I understand from the stackoverflow post I mentioned above that the ffmpeg static build needs to be on my device otherwise my app cannot use it.

  



  However I'm unsure how to get it in the /data/data/com.example.zovideo folder as needed.

  



  I have done is download the latest static ffmpeg build from http://ffmpeg.gusari.org/static/ and copied it into my libs/armeabi and libs/armeabi-v7a folders but this obviously hasn't succeeded in getting into the data/data folder when my app is installed onto my device. 
(I feel like I'm being an idiot by copy/pasting the files but I don't know what else to do. I don't know how to compile it myself - I have compiled ffmpeg using a Roman10 tutorial but this produces .so files which from which I understand is not what I need)

  



  So I'm a little stuck.
Any advice is greatly appreciated. Thanks