Recherche avancée

Sur d’autres sites (16134)

• FFmpeg + iOS + lossy cellular connections

  9 novembre 2014, par Moss

  I am able to play an RTMP audio + video real-time stream on iOS with FFmpeg. Works fantastic when everything is on a solid WiFi connection.

  When I switch to a cellular connection (great signal strength and LTE/4G), av_read_frame() will intermittently block for an unacceptable amount of time. From what I can tell, it’s not that the cellular data connection just dropped, because I can reconnect immediately and start downloading more packets. In some cases, I’ve clocked 30+ seconds of hang time before it returns the next frame. When the next frame finally comes in, my real-time video stream is permanently delayed by the amount of time that av_read_frame() blocked.

  I attempted a work-around by using the AVIOInterruptCB interrupt callback to abort av_read_frame() if the function takes longer than 1 second to return. Here’s what that code looks like :

  - (void)readPackets {
  
      // Make sure FFmpeg calls our interrupt periodically
  
      _context->interrupt_callback.callback = interrupt_cb;
  
      _context->interrupt_callback.opaque = self;
  
  
  
      dispatch_async(_readPacketQueue, ^(void) {
  
          int err;
  
  
  
          while(true) {
  
              _readFrameTimeStamp = [[NSDate date] timeIntervalSince1970];
  
              err = av_read_frame(_context, &packet);
  
              _readFrameTimeStamp = 0;
  
  
  
              if(err) {
  
                  // Error - Reconnect the entire stream from scratch, taking 5-10 seconds
  
                  // And we know when av_read_frame() was aborted
  
                  // because its error code is -1414092869 ("EXIT")
  
              }
  
              else {
  
                  // Play this audio or video packet
  
              }
  
          }
  
     });
  
  }
  
  
  
  /**
  
   * Interrupt
  
   * @return 1 to abort the current operation
  
   */
  
  static int interrupt_cb(void *decoder) {
  
      if(decoder) {
  
          if(_readFrameTimeStamp != 0) {
  
              if([[NSDate date] timeIntervalSince1970] - _readFrameTimeStamp > 1) {
  
                  // Abort av_read_frame(), it's taking longer than 1 second
  
                  return 1;
  
              }
  
          }
  
      }
  
  }

  This definitely aborts av_read_frame() after 1 second, but unfortunately after I do this, future attempts to call av_read_frame() result in EIO errors (-5), which indicates that the connection has been severed.

  As a result, I am forced to fully reconnect the viewer, which takes 5-10 seconds. (avformat_open_input() takes 3-4 seconds, and then find the stream info again takes 2-3 seconds, and then start reading frames).

  The 5-10 second delay to fully reconnect is much better than waiting more than 10 seconds for av_read_frame() to unblock, and it’s much better than the real-time stream being delayed by a significant amount. But it’s much worse than being able to retry av_read_frame() immediately.

  From a cellular user’s perspective, their video locks up intermittently for 5-10 seconds while we reconnect the stream in the background from scratch, which isn’t a good user experience.

  What strategies are there to better way to manage av_read_frame() on a lossy cellular connection ?
  (Or strategies to improve the reconnect time ?)

• How to pass command line arguments to FFMpeg in iOS

  23 septembre 2014, par Arif Nadeem

  This is a beginner question, since I am new to iOS(I started it today), so please pardon my ignorance and lack of iOS knowledge.

  After building and successfully using FFMpeg for Android I wanted to do the same for iOS.
  So I built FFMpeg successfully for iOS by following this link, but after all that pain I am confused as how to use FFMpeg in iOS, I mean how can I pass command line arguments to libffmpeg.a file ?

  I am assuming that there must be a way to run the .a file as an executable and then pass command line arguments and hope for FFMpeg to do the magic, I did the same in Android and it worked beautifully.

  I am also aware that I can use ffmpeg.c class and use its main method, but the question remains ; how do I pass those command line arguments ?

  Is there something I am supposed to be aware of here, is the thing what I am doing now correct or am I falling short on my approach ?

  I wanted to mix two audio files, so the command for doing that would be ffmpeg -i firstSound.wav -i secondSound.wav -filter_complex amix=inputs=2:duration=longest finalOutput.wav, how do I do the same in iOS ?

  Can someone please shed some light on this ?

• How do I use ffmpeg4android in an ADT project ?

  16 janvier 2013, par mystafer

  I used the project FFmpeg4Android on sourceforge to build the FFmpeg .so shared library files. However, I am having trouble using them in an ADT Java application. I created a simple JNI call that attempts to call av_register_all and I get library errors.

  When I run the application on my Nexus 7 I am told that it is unable to load library libavformat-HEAD-1.0.so

  So I tried to load this via the System.loadLibrary method and I was unable to find libavcodec-HEAD-1.0.so. Working my way back in this manner I eventually attempted to load libavutil-HEAD-1.0.so which yielded an error 'cannot locate symbol "__strchr_chk"'.

  This is my Java class :

  public class LibavcodecTest {
  
      public static native void avRegisterAll();
  
  
  
      static {
  
          System.loadLibrary("avutil-HEAD-1.0");
  
          System.loadLibrary("avcodec-HEAD-1.0");
  
          System.loadLibrary("avformat-HEAD-1.0");
  
          System.loadLibrary("LibavcodecTest");
  
      }
  
  }

  Update

  I contacted the developer that maintains ffmpeg4android and he was able to direct me to change the version of the android source I was building against to the same as my device which worked to allow my to call av_register_all successfully.

  However, now I get a crash calling avformat_open_input where I receive "Fatal signal 11 (SIGSEGV)".

  My search on the web makes me believe this is a memory access issue. Does anybody know if this may be resolved by loading the shared libraries differently ?