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• GC and onTouch cause Fatal signal 11 (SIGSEGV) error in app using ffmpeg through ndk

  30 janvier 2015, par grzebyk

  I am getting a nasty but well known error while working with FFmpeg and NDK :

  A/libc(9845): Fatal signal 11 (SIGSEGV), code 1, fault addr 0xa0a9f000 in tid 9921 (AsyncTask #4)

  UPDATE

  After couple hours i found out that there might be two sources of the problem. One was related to multithreading. I checked it and I fixed it. Now the app crashes ONLY when the video playback (ndk) is on.

  I put a "counter" in touch event

    surfaceSterowanieKamera.setOnTouchListener(new View.OnTouchListener() {
  
              int counter = 0;
  
              @Override
  
              public boolean onTouch(View v, MotionEvent event) {             
  
                  if ((event.getAction() == MotionEvent.ACTION_MOVE)){
  
                      Log.i(TAG, "counter = " + counter);
  
                      //cameraMover.setPanTilt(some parameters);
  
                      counter++;
  
                   }

  And I started disabling other app functionalities one by one, but no video. I found out, that with every single functionality less, it takes app longer to crush - counter reaches higher values. After turning off everything besides video playback and touch interface (cameraMover.setPanTilt() commented out) the app crushes usually when counter is between 1600 - 1700.

  In such case logcat shows the above error and GC related info. For me it seems like GC is messing up with the ndk.

  01-23 12:27:13.163: I/Display Activity(20633): n = 1649
  
  01-23 12:27:13.178: I/art(20633): Background sticky concurrent mark sweep GC freed 158376(6MB) AllocSpace objects, 1(3MB) LOS objects, 17% free, 36MB/44MB, paused 689us total 140.284ms
  
  01-23 12:27:13.169: A/libc(20633): Fatal signal 11 (SIGSEGV), code 1, fault addr 0x9bd6ec0c in tid 20734 (AsyncTask #3)

  Why is GC causing problem with ndk part of application ?

  ---

  ORIGINAL PROBLEM

  What am I doing ?

  I am developing an application that streams live video feed from a webcam and enables user to pan and tilt the remote camera. I am using FFmpeg library built with NDK to achieve smooth playback with little delay.

  I am using FFMpeg library to connect to the video stream. Then the ndk part creates bitmap, does the image processing and render frames on the SurfaceView videoSurfaceView object which is located in the android activity (java part).

  To move the webcam I created a separate class - public class CameraMover implements Runnable{/**/}. This class is a separate thread that connects through sockets with the remote camera and manages tasks connected ONLY with pan-tilt movement.

  Next in the main activity i created a touch listener

  videoSurfaceView.setOnTouchListener(new View.OnTouchListener() {/**/
  
  cameraMover.setPanTilt(some parameters);
  
  /**/}

  which reads user’s finger movement and sends commands to the camera.

  All tasks - moving camera around, touch interface and video playback are working perfectly when the one of the others is disabled, i.e. when I disable possibility to move camera, I can watch video streaming and register touch events till the end of time (or battery at least). The problem occurs only when task are configured to work simultaneously.

  I am unable to find steps to reproduce the problem. It just happens, but only after user touches the screen to move camera. It can be 15 seconds after first interaction, but sometimes it takes app 10 or more minutes to crash. Usually it is something around a minute.

  What have I done to fix it ?

  • I tried to display millions of logs in logcat to find an error but
    the last log was always different.
  • I created a transparent surface, that I put over the videoSurfaceView and assigned touch listener to it. It all ended in the same error.
  • As I mentioned before, I turned off some functionalities to find which one produces the error, but it appears that error occurs only when everything is working simultaneously.

  Types of the error

  Almost every time the error looks like this :

  A/libc(11528): Fatal signal 11 (SIGSEGV), code 1, fault addr 0x9aa9f00c in tid 11637 (AsyncTask #4)

  the difference between two errors is the number right after libc, addr number and tid number. Rarely the AsyncTask number varies - i received #1 couple times but I was unable to reproduce it.

  Question

  How can i avoid this error ? What can be the source of it ?

• Live streaming video on multiple platforms [closed]

  4 mars 2019, par Nikolay Nikolov

  I want to build an application similar to Twitch/YouTube, which mainly offers two things (and a couple of other, but they are not related to the question) - to record and send live streams and to watch other people’s live streams. Basically, if I wanted to build Twitch, where would I start in terms of protocols and back-end libraries for the processing and sending/receiving of video segments (more detailed questions follow) ? I am new to the video streaming software development and need a bit of guidance on where/how to start.

  Here are the details/requirements :

  • Video and audio
  • Scalability and low latency are more important than supreme quality
  • Adaptive bit-rate
  • No services like Wowza and such (I am willing to build the whole structure)
  • Has to work on iOS and Android (Desktop support is not as important)
  • The users should be able to watch every stream and every user should be able to stream through his camera
  • VOD is not as important
  • Going back in the stream is not as important

  If I have it right, this is how the whole process should work :

  • Android/iOS camera records video
  • Simultaneously the app saves every x seconds as a single segment and sends it to the server
  • Server processes the video in different bit rates and saves them
  • Another user requests stream based on the bandwidth of its internet connection
  • Server responds with a playlist of segments and sends each new chunk of video to the user

  Questions :

  • What protocols should I be using (HLS, MPEG-DASH, WebRTC, RTSP, etc.) and do these protocols have implementations on Android/iOS or do I have to implement them myself ?
  • What books/other resources would you recommend ?

  Thank you very much for reading my question and I look forward to reading your answers !

• Resize videos and keep codecs using PHP-FFMpeg

  30 décembre 2019, par tmp_hallenser

  I’m trying to resize a couple of videos (with different codecs) using PHP-FFMpeg. The official documentation gives the following example (see https://github.com/PHP-FFMpeg/PHP-FFMpeg)

  $ffmpeg = FFMpeg\FFMpeg::create();
  
  $video = $ffmpeg->open('video.mpg');
  
  $video
  
      ->filters()
  
      ->resize(new FFMpeg\Coordinate\Dimension(320, 240))
  
      ->synchronize();
  
  $video
  
      ->frame(FFMpeg\Coordinate\TimeCode::fromSeconds(10))
  
      ->save('frame.jpg');
  
  $video
  
      ->save(new FFMpeg\Format\Video\X264(), 'export-x264.mp4')
  
      ->save(new FFMpeg\Format\Video\WMV(), 'export-wmv.wmv')
  
      ->save(new FFMpeg\Format\Video\WebM(), 'export-webm.webm');

  Since I don’t want to specify the codec (take the same as the source file), I was trying to create a copy-format and use this format instead for the save command.

  class MOVFormat extends FFMpeg\Format\Video\DefaultVideo
  
  {
  
      public function __construct($audioCodec = 'copy', $videoCodec = 'copy')
  
      {
  
          $this
  
              ->setAudioCodec($audioCodec)
  
              ->setVideoCodec($videoCodec);
  
      }
  
  
  
      public function supportBFrames()
  
      {
  
          return false;
  
      }
  
  
  
      public function getAvailableAudioCodecs()
  
      {
  
          return ['copy'];
  
      }
  
  
  
      public function getAvailableVideoCodecs()
  
      {
  
          return ['copy'];
  
      }
  
  }

  This results in Filtergraph '[in]scale=320:240 [out]' was defined for video output stream 0:0 but codec copy was selected. and Filtering and streamcopy cannot be used together.

  Technically, it should be possible to resize without specifying the codec if I look at this reply : https://superuser.com/a/624564

  Any help is appreciated !