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• Real time compression/encoding using ffmpeg in objective c

  20 février 2014, par halfwaythru

  I have a small application written in Objective-c that looks for the video devices on the machine and allows the user to record video. I need to be able to compress this video stream in real time. I do not want to save the whole video, I want to compress it as much as possible and only write out the compressed version.

  I also don't want to use the AVFoundation's build in compression methods and need to use a third party library like ffmpeg.

  So far, I have been able to record the video and get individual frames using 'AVCaptureVideoDataOutputSampleBufferDelegate' in this method :

  - (void)captureOutput:(AVCaptureOutput *)captureOutput
  
     didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
  
     fromConnection:(AVCaptureConnection *)connection

  So I have a stream of images basically, and I want to throw them into ffmpeg (which is all set up on my machine). Do I need to call a terminal command to do this ? And if I do, how do I use the image stack as my input to the ffmpeg command, instead of the video. Also, how do I combine all the little videos in the end ?

  Any help is appreciated. Thanks !

• Extracting audio from video using Xuggler

  13 février 2014, par Sudh

  I am trying to extract audio(mp3) from a video file (flv), but I keep getting Exceptions :

  05:02:10.326 [AWT-EventQueue-0] ERROR org.ffmpeg - [aac @ 000000000043B3F0] channel element 0.0 is not allocated
  java.lang.IllegalArgumentException : stream[0] is not video

  I tried with this :

  public void runExample(int a) {
  
      String sourceUrl="F:\\Software\\library\\test1.mp4";
  
      String destUrl="F:\\Software\\library\\test1.flv";
  
      IMediaReader reader = null; 
  
      IMediaWriter writer = null; 
  
      try { 
  
          reader = ToolFactory.makeReader(sourceUrl); 
  
          writer = ToolFactory.makeWriter(destUrl, reader); 
  
          reader.addListener(writer); 
  
          int sampleRate = 44100;
  
          int channels = 1;
  
          //writer.addAudioStream(0, 0, ICodec.ID.CODEC_ID_MP3, channels, sampleRate);
  
  
  
          while (reader.readPacket() == null) ; 
  
          //Should IMediaReader automatically call close(), only if ERROR_EOF (End of File) is returned from readPacket().
  
          reader.setCloseOnEofOnly(false); 
  
          //If false the media data will be left in the order in which it is presented to the IMediaWriter.
  
          //If true IMediaWriter will buffer media data in time stamp order, and only write out data when it has at least one same time or later packet from all streams.
  
          writer.setForceInterleave(false);
  
          System.out.println("closed...");
  
      } catch (Exception ex) { 
  
          ex.printStackTrace(); 
  
      }
  
  }

  Also When I try this :

  public String seperateAudioStream(String pathToAudioFile)
  
      { String sourceUrl="F:\\Software\\library\\test1.mp4";
  
          String destUrl="F:\\Software\\library\\test1.mp3";
  
  
  
          IMediaReader reader = ToolFactory.makeReader(sourceUrl);
  
          reader.open();
  
          IMediaWriter writer = ToolFactory.makeWriter(destUrl,reader);
  
          reader.addListener(writer);
  
          int sampleRate = 44100;
  
          int channels = 1;
  
          writer.addVideoStream(0, 0, ICodec.ID.CODEC_ID_MP3, channels, sampleRate);
  
  
  
          while (reader.readPacket() == null);
  
          return null;
  
          IContainer container = IContainer.make();
  
          int result = container.open(sourceUrl, IContainer.Type.READ, null);
  
           // check if the operation was successful
  
            if (result<0)
  
                throw new RuntimeException("Failed to open media file");
  
  
  
            int numStreams = container.getNumStreams();
  
  
  
            int audioStreamId = -1;
  
  
  
            IContainer writer = IContainer.make();
  
            writer.open(destUrl, IContainer.Type.WRITE, IContainerFormat.make());
  
  
  
  
  
  
  
            for (int i=0; i= 0){
  
  
  
                            if(packet.getStreamIndex() == audioStreamId)
  
                            {
  
                                if(coder.isOpen()){
  
  
  
                                    System.out.println("Writing audio ...");
  
                                    writer.writePacket(packet);
  
  
  
                                } else {throw new RuntimeException("Could not open Coder"); }
  
                            }
  
                        }
  
                    }else {throw new RuntimeException("Header not Written for writer container.");}
  
                }
  
  
  
                coder.close();
  
                audioCoder.close();
  
            }
  
            writer.writeTrailer();
  
            writer.close();
  
          return null;
  
  
  
     }

  I get error : ERROR org.ffmpeg channel element 0.0 is not allocated multiple times

  The documentation is unclear to say the least.. xuggler's website looks sick and none of the videos given in tutorial play... even on stack overflow most of the questions related to this are unanswered.

• How to load file in ffmpeg in chunks ?

  18 mars, par developer1

  I'm having a problem when loading a larger file with ffmpeg in safari mobile, it crashes while doing that.

  


  Currently I'm loading the whole file at once await ffmpeg.writeFile(inputFileName, await fetchFile(file)); and to my understanding safari tries to load it in-memory in one go and fails.

  


  How can I work around this issue ? Maybe split the file to chunks ? Maybe streaming ?

  


  Thank you.