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• FFMpeg + OpenAL

  24 juillet 2013, par Dekowta

  I've been having a problem decoding different codecs into PCM 16 little-endian which is the supported format for OpenAL (I believe that is correct).

  I am using the windows pre-compiled libraries for FFMpeg (dont know if that effects anything).

  The code I have so far is here http://pastebin.com/T4wGL72a

  I have aiff and wav working (though with single channel OpenAL wants to have half the frequency and im not really sure why).

  The main problem is encoded audio files.

  mp3 files play sometimes (sometime get missing header) but end up stuttering with noise and are high pitched.

  ac3 files played the first preloaded buffers and then the frame would not have any more decoded data in the data array (did not check to see if the packet fetched encoded data or not).

  ogg files are the same as ac3

  m4a files would never finish the frame so I have no idea what happens when they do.

  wma files stutter and have a lot of noise but it is not high pitched like mp3 files

  I don't work with audio very often so its difficult for me to get my head round it and this is also the first time I've worked with FFMpeg.

  I'm sure there is something i'm doing very wrong I just need a hand on pointing out where it is.

  Thanks

  Chris.

• Better performance for ffmpeg decoding editing image contrast for every frame

  6 août 2013, par Simone M

  i'm developing an rtsp player using ffmpeg library and i must edit contrast image for every frame of video, searching the web i found this code for edit contrast :

  - (UIImage*)contrast
  
  {    
  
      CIImage *beginImage = [CIImage imageWithCGImage:[self CGImage]];
  
      CIContext *context = [CIContext contextWithOptions:nil];
  
  
  
      CIFilter *filter = [CIFilter filterWithName:@"CISepiaTone" 
  
                                    keysAndValues: kCIInputImageKey, beginImage, 
  
                          @"inputIntensity", [NSNumber numberWithFloat:0.8], nil];
  
      CIImage *outputImage = [filter outputImage];
  
  
  
      CGImageRef cgimg = 
  
      [context createCGImage:outputImage fromRect:[outputImage extent]];
  
      UIImage *newImg = [UIImage imageWithCGImage:cgimg];
  
  
  
      self = newImg;
  
  
  
      CGImageRelease(cgimg);
  
      return self;
  
  }

  it works perfectly, but on iPad i lose performance and when decoding video are show a lot of noise on screen. There is a better way in performance to modify contrast for image ??

• qdm2 : check and reset dithering index per channel

  27 juin 2013, par Luca Barbato

  qdm2 : check and reset dithering index per channel
  Checking per subband would have the index exceed the
  
  dithering noise table size.
  Reported-by : Mateusz "j00ru" Jurczyk and Gynvael Coldwind
  
  CC : libav-stable@libav.org
  

  • [DBH] libavcodec/qdm2.c