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• merge segments with ffmpeg causes small cracks in the audio

  14 octobre 2019, par Paulo Medeiros

  To speed up the delivery of videos on my platform I split the uploaded medias into segments of up to 120 seconds and process them simultaneously on several machines.

  After processing, I put the pieces back together with "-f concat".

  Unfortunately, new media is generated with small cracks in the audio (they occur exactly at the junction). I haven’t found a filter / command yet to end the problem. Does anybody know how to solve this ?

  Note : I am using ffmpeg 3.4.1

  This is the command I make to split the media :

  ffmpeg -hide_banner -fflags +genpts -avoid_negative_ts make_zero -y -v error -i /video/somevideo.mov -map 0:v? -map 0:a? -c copy -f segment -segment_time 120 -segment_format matroska -reset_timestamps 1 -segment_list_type ffconcat -segment_list /video/segment_map.ffcat /video/segment%03d

  A short example of the command used to process a segment

  some variables change according to the resolution

  ffmpeg -y -hide_banner -v error -probesize 10M -analyzeduration 10M -itsoffset 0.066 -i /video/segment000 -c:v libx264 -preset fast -profile:v high -crf 23 -r 117375/3916 -maxrate 1500000 -bufsize 2250000 -g 58 -keyint_min 58 -sc_threshold 0 -bf 3 -b_strategy 2 -refs 10 -vf scale="iw*sar:ih,scale=trunc(oh*a/2)*2:540" -pix_fmt yuv420p -max_muxing_queue_size 5000 -strict -2 -c:a aac -b:a 128000 -ar 44100  -f mp4 /video/transcode/segment000

  to finalize how do I join the segments

  ffmpeg -hide_banner -v error -f concat -safe 0 -y -i /video/transcode/segment_map.ffcat -c copy -movflags +faststart /video/transcoded.mp4

• How to stream live video from DJI Professional 3 camera ?

  5 juin 2017, par raullalves

  I have to get the live stream video from DJI Phantom 3 camera in my C++ application, in order to do a Computer Vision processing in OpenCV.

  First I tried sending the H264 raw data through an UDP socket, inside this callback :

          mReceivedVideoDataCallBack = new CameraReceivedVideoDataCallback() {
  
  
  
          @Override
  
          public void onResult(byte[] videoBuffer, int size) {
  
              //Here, I call a method from a class I created, that sends the buffer through UDP
  
              if (gravar_trigger) controleVideo.enviarFrame(videoBuffer, size);
  
  
  
              if (mCodecManager != null)  mCodecManager.sendDataToDecoder(videoBuffer, size);
  
  
  
          }
  
  
  
      };

  That communication above works well. However, I haven’t been able to decode that UDP H264 data in my C++ desktop application. I have tested with FFmpeg lib, but couldn’t get to alocate an AVPacketwith my UDP data, in order to decode using avcodec_send_packet and avcodec_receive_frame. I also had problems with AVCodecContext, since my UDP communication wasn’t a stream like RTSP, where it could get information about its source. Therefore, I had to change how I was trying to solve the problem.

  Then, I found libstreaming, in which can be associate to stream the android video camera to a Wowza Server, creating something like a RTSP stream connection, where the data could be obtained in my final C++ application easily using OpenCV videoCapture. However, libstreaming uses its own surfaceView. In other words, I would have to link the libstreaming surfaceView with the DJI Drone’s videoSurface. I’m really new to Android, so don’t have any clue of how to do that.

  To sum up, is that the correct approach ? Someone has a better idea ? Thanks in advance

• How to stream live video from DJI Professional 3 camera ?

  29 avril 2017, par raullalves

  I have to get the live stream video from DJI Phantom 3 camera in my C++ application, in order to do a Computer Vision processing in OpenCV.

  First I tried sending the H264 raw data through an UDP socket, inside this callback :

          mReceivedVideoDataCallBack = new CameraReceivedVideoDataCallback() {
  
  
  
          @Override
  
          public void onResult(byte[] videoBuffer, int size) {
  
              //Here, I call a method from a class I created, that sends the buffer through UDP
  
              if (gravar_trigger) controleVideo.enviarFrame(videoBuffer, size);
  
  
  
              if (mCodecManager != null)  mCodecManager.sendDataToDecoder(videoBuffer, size);
  
  
  
          }
  
  
  
      };

  That communication above works well. However, I haven’t been able to decode that UDP H264 data in my C++ desktop application. I have tested with FFmpeg lib, but couldn’t get to alocate an AVPacketwith my UDP data, in order to decode using avcodec_send_packet and avcodec_receive_frame. I also had problems with AVCodecContext, since my UDP communication wasn’t a stream like RTSP, where it could get information about its source. Therefore, I had to change how I was trying to solve the problem.

  Then, I found libstreaming, in which can be associate to stream the android video camera to a Wowza Server, creating something like a RTSP stream connection, where the data could be obtained in my final C++ application easily using OpenCV videoCapture. However, libstreaming uses its own surfaceView. In other words, I would have to link the libstreaming surfaceView with the DJI Drone’s videoSurface. I’m really new to Android, so don’t have any clue of how to do that.

  To sum up, is that the correct approach ? Someone has a better idea ? Thanks in advance