public static CloudBlockBlob GetBlob(string containerName, string blobName)
{
var blobContainer = AzureStorageUtils.GetCloudBlobContainer(containerName);
return(blobContainer.GetBlockBlobReference(blobName));
}
public async Task <RecordingDetails> Transcode(IEnumerable <KeyValuePair <string, MemoryStream> > tracks, string userIdKey, string timeKey, string extension)
{
RecordingDetails result = null;
// ffmpeg.exe works with files. Produce file paths.
var workDirPath = GeneralUtils.GetAppDataDir();
var fileNamePrefix = userIdKey + "_" + timeKey;
var trackItems = tracks
.Select(i => new TrackItem
{
Name = i.Key,
Stream = i.Value,
OriginalFile = Path.Combine(workDirPath, String.Format("{0}_{1}.{2}", fileNamePrefix, i.Key, extension)),
IntermidiateFile = Path.Combine(workDirPath, String.Format("{0}_{1}_intermidiate.mp3", fileNamePrefix, i.Key)),
})
.ToList();
var inputListFilePath = Path.Combine(workDirPath, fileNamePrefix + ".txt");
var outputFilePath = Path.ChangeExtension(inputListFilePath, ".mp3");
const string resultFileName = "result";
var outputBlobName = ExerciseUtils.FormatBlobName(userIdKey, timeKey, resultFileName, "mp3");
var logBlobName = ExerciseUtils.FormatBlobName(userIdKey, timeKey, resultFileName, "log");
try
{
// Save the original tracks to the disk.
foreach (var i in trackItems)
{
using (FileStream stream = new FileStream(i.OriginalFile, FileMode.Create, FileAccess.Write))
{
i.Stream.WriteTo(stream);
}
}
// Convert to MP3.
// ffmpeg fails to concatenate AMRs, the error text is misleading "mylistfile.txt: Input/output error". We convert each file separately, then concatenate MP3s.
foreach (var i in trackItems)
{
// Increase audio volume by 10dB, convert to MP3 CBR 32kbit/s.
var arguments = String.Format("-i \"{0}\" -af \"volume=10dB\" -b:a 32k \"{1}\"", i.OriginalFile, i.IntermidiateFile);
i.Log = RecordingUtils.RunFfmpeg(arguments);
}
// Pass the file names to concatenate to ffmpeg.exe in a text file.
var inputListLines = trackItems.Select(i => String.Format("file '{0}'", i.IntermidiateFile));
File.WriteAllLines(inputListFilePath, inputListLines);
// Concatenate MP3s. Do not re-encode, copy existing streams as is.
var concatArguments = String.Format("-f concat -i \"{0}\" -c copy \"{1}\"", inputListFilePath, outputFilePath);
var resultLog = RecordingUtils.RunFfmpeg(concatArguments);
var separator = Environment.NewLine + "----------------------------------------" + Environment.NewLine;
var logText = String.Join(separator, trackItems.Select(i => i.Log))
+ separator + String.Join(Environment.NewLine, inputListLines)
+ separator + resultLog;
var containerName = AzureStorageUtils.ContainerNames.Artifacts;
var taskMp3 = AzureStorageUtils.UploadFromFileAsync(outputFilePath, containerName, outputBlobName, "audio/mpeg");
var taskLog = AzureStorageUtils.UploadTextAsync(logText, containerName, logBlobName, "text/plain");
// Upload the blobs simultaneously.
await Task.WhenAll(taskMp3, taskLog);
// Get the recording durations.
var trackDurations = trackItems
.Select((i) =>
{
var trackDuration = RecordingUtils.GetDurationFromFfmpegLogOrMp3File(i.Log, i.IntermidiateFile);
return(new KeyValuePair <string, decimal>(i.Name, trackDuration));
})
.ToDictionary(i => i.Key, i => i.Value)
;
var duration = RecordingUtils.GetDurationFromFfmpegLogOrMp3File(resultLog, outputFilePath);
// The JSON encoder with default settings doesn't make upper-case -> lower-case letter conversion of property names. The receiving side is case-sensitive.
result = new RecordingDetails
{
BlobName = outputBlobName,
TotalDuration = duration,
TrackDurations = trackDurations,
};
}
finally
{
// Clean up the local disk.
foreach (var i in trackItems)
{
File.Delete(i.OriginalFile);
File.Delete(i.IntermidiateFile);
}
File.Delete(inputListFilePath);
File.Delete(outputFilePath);
}
return(result);
}