Previous page: Daily Crap 2010-01-24
Next page: Daily Crap 2010-02-06

Daily Crap 2010-02-02

  1. When I save an FLV file from YouTube and export its audio as WAV with VLC, there's usually a lot of clipping. Even if you export as floats (so that the clipped data is still there), when you load the file in Audacity, Audacity will hard clip at [-1, 1]. To get around this, I wrote a short C program using libsndfile to scale the raw float data.

    #include <stdio.h>
#include <stdlib.h>
#include <sndfile.h>

int
main(int argc, char *argv[])
{
  SF_INFO infoIn, infoOut;
  SNDFILE *wavIn, *wavOut;
  int i;
  float frame[2 /* max channels */];

  infoIn.format = 0; /* auto-detect */
  wavIn = sf_open("beat.wav", SFM_READ, &infoIn);
  if(!wavIn) {
    printf("couldn't open beat.wav\n");
    return 1;
  }

  printf("input channels: %d\n", infoIn.channels);

  infoOut.samplerate = infoIn.samplerate;
  infoOut.channels = infoIn.channels;
  infoOut.format = SF_FORMAT_WAV | SF_FORMAT_FLOAT;
  wavOut = sf_open("beat-out.wav", SFM_WRITE, &infoOut);
  if(!wavOut) {
    printf("couldn't open beat-out.wav\n");
    return 1;
  }

  while(sf_read_float(wavIn, frame, infoIn.channels) > 0) {
    for(i = 0; i < infoIn.channels; i++)
      frame[i] *= 0.3;
    sf_write_float(wavOut, frame, infoIn.channels);
  }

  printf("done\n");

  sf_close(wavOut);
  sf_close(wavIn);

  return 0;
}

Posted Feb 02, 2010, in the morning.

Comments

Click here to view the comments on this post.