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• NSTask and FFMpeg losing output

  16 novembre 2011, par Morgan

  I'm trying to call ffmpeg from NSTask in objective-c. I execute the ffmpeg command in terminal and it works flawlessly every time. I make the same command using NSTask, and it never gives me the whole output. It cuts it off half way through the output, at a seemingly random spot every time. Here is my code.

      - (void)applicationDidFinishLaunching:(NSNotification *)aNotification
  
  {
  
      NSString* ffmpegPath = [[NSBundle mainBundle] pathForResource:@"ffmpeg" ofType:@""];
  
      NSString* path = @"test.mov";
  
  
  
      NSTask *task = [[NSTask alloc] init];
  
      NSArray *arguments = [NSArray arrayWithObjects: @"-i", path, nil];
  
      NSPipe *pipe = [NSPipe pipe];
  
      NSFileHandle * read = [pipe fileHandleForReading];
  
  
  
      [task setLaunchPath: ffmpegPath];
  
      [task setArguments: arguments];
  
      [task setStandardOutput: pipe];
  
      [task launch];
  
      [task waitUntilExit];
  
  
  
      NSData* data = [read readDataToEndOfFile];
  
      NSString* stringOutput = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
  
  
  
  
  
      NSLog(@"%@", stringOutput);
  
      NSLog(@"%i", [task terminationStatus]);
  
      NSLog(@"DONE");
  
  }

• Record stream from camera to file / live stream

  8 juillet 2015, par sandman

  I’m trying to stream my camera feed to a webpage. For this I’m trying to use FFmpeg to encode the data from the camera preview and output to a file. (I’m new to this, so I’m only trying to write to a file now)

  The camera feed is captured and it starts writing to a flv file but, it freezes my app after a few seconds and the resulting flv is about half a second long.

  bos is a BufferedOutputStream which servers as an input stream for the Ffmpeg ProcessBuilder.

  When a button is clicked, the Ffmpeg process is executed and the writing begins.
  But as I said, it freezes the app after a while. I tried running the Ffmpeg process in an AsyncTask, but it keeps saying FileDescriptor closed, but the app does not freeze when I do it this way, and there is no output as well.

  Here is my onPreviewFrame() :

  public void onPreviewFrame(byte[] b, Camera c) {
  
      if (recording) {
  
          int previewFormat = p.getPreviewFormat();
  
          Log.v(LOGTAG, "Started Writing Frame");
  
  
  
          im = new YuvImage(b, previewFormat, p.getPreviewSize().width, p.getPreviewSize().height, null);
  
          Rect r = new Rect(0, 0, p.getPreviewSize().width, p.getPreviewSize().height);
  
          if (bos != null)
  
              im.compressToJpeg(r, 40, bos);
  
          im = null;
  
  
  
          Log.v(LOGTAG, "Finished Writing Frame");
  
      }
  
  }

  If I can get this fixed, I can probably move on to live streaming.

• rv34 : use ff_mpeg_update_thread_context only when decoder is fully initialized

  21 août 2014, par Janne Grunau

  rv34 : use ff_mpeg_update_thread_context only when decoder is fully initialized
  MpegEncContext based decoders are only fully initialized after the first
  
  ff_thread_get_buffer() call. The RV30/40 decoders may fail before a frame
  
  buffer was requested. ff_mpeg_update_thread_context() fails on half
  
  initialized MpegEncContexts. Since this can only happen before a the
  
  first frame was decoded there is no need to call
  
  ff_mpeg_update_thread_context().
  Based on patches by John Stebbins and tested by John Stebbins.
  CC : libav-stable@libav.org
  

  • [DBH] libavcodec/rv34.c