public static JObject GenerateRichMetadata(string filePath)
{
//Get file info
var info = AudioFileInfo.GetAudioFileInfo(filePath);
//Get details
float durationSeconds = float.Parse(info.data["STREAM"]["duration"]);
int sampleRate = int.Parse(info.data["STREAM"]["sample_rate"]);
//Determine how many samples will be in each data point
//This will break for very short audio files, but this will likely never be encountered
float samplesPerDataPoint = (float)(sampleRate * durationSeconds) / (float)RESOLUTION;
if (samplesPerDataPoint < 1)
{
throw new Exception("Audio is too short!");
}
//Start FFMPEG and instruct it to output in 8-bits-per-sample mono. This will mix down stereo tracks to mono
string args = $"-i \"{filePath}\" -f s8 -acodec pcm_s8 -ac 1 -";
Process ffmpeg = Process.Start(new ProcessStartInfo
{
FileName = Program.site.config.ffmpeg_path,
Arguments = args,
UseShellExecute = false,
RedirectStandardOutput = true
});
//Open file where we'll save this info
long read = 0;
using (FileStream fs = new FileStream(filePath + ".audiothumb", FileMode.Create))
{
//Run for resolution
for (int j = 0; j < RESOLUTION; j += 1)
{
//Deteremine how many to read
//Find the end byte
long endByte = (long)(j * samplesPerDataPoint);
//Find the max in these samples
byte max = 0;
while (read < endByte)
{
int value = (sbyte)ffmpeg.StandardOutput.BaseStream.ReadByte();
max = Math.Max(max, (byte)Math.Abs(value));
read++;
}
//Write
fs.WriteByte(max);
}
}
//Wait for end
ffmpeg.StandardOutput.BaseStream.Close();
ffmpeg.WaitForExit();
//Create rich metadata
JObject meta = new JObject();
meta["DURATION_SECONDS"] = durationSeconds;
meta["SAMPLE_RATE"] = sampleRate;
meta["CHANNELS"] = int.Parse(info.data["STREAM"]["channels"]);
meta["AUDIO_THUMB_RESOLUTION"] = RESOLUTION;
meta["AUDIO_THUMB_VERSION"] = 1;
meta["AUDIO_THUMB_GENERATED_AT"] = DateTime.UtcNow.Ticks;
return(meta);
}
