title: CMTime / CMTimeMake noob question
body: <p>CMTimeMake is not giving me the results I expect.  The following code:</p>
  
  <pre><code>CMTime testTime = CMTimeMake(0, 30);
  NSLog(@"testTime w/ input 0, 30: value: %d, timescale %d, seconds: %f",
         testTime.value, testTime.timescale,
        (float) testTime.value / testTime.timescale);
  
  testTime = CMTimeMake(1, 30);
  NSLog(@"testTime w/ input 1, 30: value: %d, timescale %d, seconds: %f",
        testTime.value, testTime.timescale,
        (float) testTime.value / testTime.timescale);
  
  testTime = CMTimeMake(15, 30);
  NSLog(@"testTime w/ input 15, 30: value: %d, timescale %d, seconds: %f",
        testTime.value, testTime.timescale,
        (float) testTime.value / testTime.timescale);
  </code></pre>
  
  <p>produces the following output:</p>
  
  <p>testTime w/ input 0, 30: value: 0, timescale 0, seconds: 0.000000</p>
  
  <p>testTime w/ input 1, 60: value: 1, timescale 0, seconds: 0.000000</p>
  
  <p>testTime w/ input 15, 60: value: 15, timescale 0, seconds: 0.000000</p>
  
  <p>Why is testTime.timescale always zero?</p>