private static AudioKeyValues GetKeyValues(AudioFileReader reader)
{
var res = new AudioKeyValues();
const double volumeThreshold = 0.009;
const double endToleranceModifier = 0.5;
var startIteration = 0;
var endIteration = 0;
var totalIterationCount = 0;
var buffer = new float[reader.WaveFormat.SampleRate];
int read;
// iterate file
do
{
read = reader.Read(buffer, 0, buffer.Length);
for (var n = 0; n < read; n++)
{
totalIterationCount++;
var volume = Math.Abs(buffer[n]);
// found start trim pos
if (volume > volumeThreshold && startIteration == 0)
{
startIteration = totalIterationCount;
}
// update end trim pos -> less threshold/strict because a longer end is not bad
if (volume > volumeThreshold * endToleranceModifier)
{
endIteration = totalIterationCount;
}
// update max volume
if (volume > res.MaxVolume)
{
res.MaxVolume = volume;
}
}
} while (read > 0);
// reset current position to start for future reads
reader.Position = 0;
if (res.MaxVolume <= 0 || res.MaxVolume > 1.0f)
{
throw new InvalidOperationException("File cannot be normalized");
}
// convert iteration# to time
var startPercent = (double)startIteration / totalIterationCount;
var endPercent = (double)endIteration / totalIterationCount;
res.StartCut = TimeSpan.FromMilliseconds(reader.TotalTime.TotalMilliseconds * startPercent);
res.EndCut = TimeSpan.FromMilliseconds(reader.TotalTime.TotalMilliseconds * endPercent);
res.EndCut = reader.TotalTime - res.EndCut;
return(res);
}
private static void NormalizeVolume(AudioFileReader reader, AudioKeyValues data)
{
reader.Volume = 1.0f / data.MaxVolume;
}