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• WebVTT Audio Descriptions for Elephants Dream

  10 mars 2015, par silvia

  When I set out to improve accessibility on the Web and we started developing WebSRT – later to be renamed to WebVTT – I needed an example video to demonstrate captions / subtitles, audio descriptions, transcripts, navigation markers and sign language.

  I needed a freely available video with spoken text that either already had such data available or that I could create it for. Naturally I chose “Elephants Dream” by the Orange Open Movie Project , because it was created under the Creative Commons Attribution 2.5 license.

  As it turned out, the Blender Foundation had already created a collection of SRT files that would represent the English original as well as the translated languages. I was able to reuse them by merely adding a WEBVTT header.

  Then there was a need for a textual audio description. I read up on the plot online and finally wrote up a time-alignd audio description. I’m hereby making that file available under the Create Commons Attribution 4.0 license. I’ve added a few lines to the medadata headers so it doesn’t confuse players. Feel free to reuse at will – I know there are others out there that have a similar need to demonstrate accessibility features.

  The post WebVTT Audio Descriptions for Elephants Dream first appeared on ginger’s thoughts.

• samplerate conversion function fails to produce an audible sound but only small pieces of audio

  2 juillet 2014, par user3749290

  playmp3() using libmpg123

  if (isPaused==0 && mpg123_read(mh, buffer, buffer_size, &done) == MPG123_OK)
  
  {
  
      char * resBuffer=&buffer[0]; //22100=0,5s
  
      buffer = resample(resBuffer,22050,22050); // I think the result is 1/2 of audio speed
  
      if((ao_play(dev, (char*)buffer, done)==0)){
  
          return 1;
  
  }

  resample() Using avcodec from ffmpeg

  #define LENGTH_MS 500       // how many milliseconds of speech to store 0,5s:x=1:44100 x=22050 sample to store
  
  #define RATE 44100      // the sampling rate (input)
  
  #define FORMAT PA_SAMPLE_S16NE  // sample size: 8 or 16 bits
  
  #define CHANNELS 2      // 1 = mono 2 = stereo
  
  
  
  struct AVResampleContext* audio_cntx = 0;
  
  //(LENGTH_MS*RATE*16*CHANNELS)/8000
  
  
  
      void resample(char in_buffer[],int out_rate,int nsamples,char out_buffer[])
  
      {
  
          //char out_buffer[ sizeof( in_buffer ) * 4];
  
          audio_cntx = av_resample_init( out_rate, //out rate
  
              RATE, //in rate
  
              16, //filter length
  
              10, //phase count
  
              0, //linear FIR filter
  
              1.0 ); //cutoff frequency
  
          assert( audio_cntx && "Failed to create resampling context!");
  
          int samples_consumed;
  
          //*out_buffer = malloc(sizeof(in_buffer));
  
          int samples_output = av_resample( audio_cntx, //resample context
  
              (short*)out_buffer, //buffout
  
              (short*)in_buffer,  //buffin
  
              &samples_consumed,  //&consumed
  
              nsamples,       //nb_samples
  
              sizeof(out_buffer)/2,//lenout sizeof(out_buffer)/2
  
              0);//is_last
  
          assert( samples_output > 0 && "Error calling av_resample()!" );
  
          av_resample_close( audio_cntx );    
  
      }

  When I run this code, the application part, the problem is that I hear the sound jerky, why ?
  The size of the array I think is right, I calculated considering that in the second half should be 22050 samples from store.

• w32threads : Use newer thread synchronization functions when targeting Vista

  6 août 2014, par Martin Storsjö

  w32threads : Use newer thread synchronization functions when targeting Vista
  When explicitly targeting Vista or newer (which only happens if the
  
  caller explicitly sets _WIN32_WINNT to a high enough value via the
  
  extra cflags option - otherwise configure script sets
  
   D_WIN32_WINNT=0x0502), we already unconditionally link to the
  
  ConditionVariable functions, since 4622f11f9.
  Similarly use the newer -Ex versions of CreateEvent, CreateSemaphore,
  
  InitializeCriticalSection and WaitForSingleObject, that all appeared
  
  in Vista. When building Windows Store applications, the older versions
  
  of these functions aren’t available, only the -Ex functions. When
  
  doing such a build, the user can set -D_WIN32_WINNT=0x0600 to
  
  forcibly use the newer functions instead.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] compat/w32pthreads.h