TTS over web-service in compressed format - web-services

Question

I have developed TTS engine in .NET. Now I want to expose it over web.
I have used the base64 string encoding to transfer the WAV format, but it is slow when I pass longer text.
Now I'm considering to build some MP3 streaming (maybe with NAudio) where I will convert the WAV formated MemoryStream into MP3 stream and pass it to the client. Does anyone has some experience with this?
Does anyone has experience how to convert WAV MemoryStream with NAudio to MP3 MemoryStream?

Answer 1

public class MP3StreamingPanel2 : UserControl
{
enum StreamingPlaybackState
{
Stopped,
Playing,
Buffering,
Paused
}
private BufferedWaveProvider bufferedWaveProvider;
private IWavePlayer waveOut;
private volatile StreamingPlaybackState playbackState;
private volatile bool fullyDownloaded;
private HttpWebRequest webRequest;
public void StreamMP32(string url)
{
Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);
SettingsSection section = (SettingsSection)config.GetSection("system.net/settings");
section.HttpWebRequest.UseUnsafeHeaderParsing = true;
config.Save();
this.fullyDownloaded = false;
webRequest = (HttpWebRequest)WebRequest.Create(url);
int metaInt = 0; // blocksize of mp3 data
webRequest.Headers.Clear();
webRequest.Headers.Add("GET", "/ HTTP/1.0");
// needed to receive metadata informations
webRequest.Headers.Add("Icy-MetaData", "1");
webRequest.UserAgent = "WinampMPEG/5.09";
HttpWebResponse resp = null;
try
{
resp = (HttpWebResponse)webRequest.GetResponse();
}
catch (WebException e)
{
if (e.Status != WebExceptionStatus.RequestCanceled)
{
//ShowError(e.Message);
}
return;
}
byte[] buffer = new byte[16384 * 4]; // needs to be big enough to hold a decompressed frame
try
{
// read blocksize to find metadata block
metaInt = Convert.ToInt32(resp.GetResponseHeader("icy-metaint"));
}
catch
{
}
IMp3FrameDecompressor decompressor = null;
try
{
using (var responseStream = resp.GetResponseStream())
{
var readFullyStream = new ReadFullyStream(responseStream);
readFullyStream.metaInt = metaInt;
do
{
if (bufferedWaveProvider != null && bufferedWaveProvider.BufferLength - bufferedWaveProvider.BufferedBytes < bufferedWaveProvider.WaveFormat.AverageBytesPerSecond / 4)
{
Debug.WriteLine("Buffer getting full, taking a break");
Thread.Sleep(500);
}
else
{
Mp3Frame frame = null;
try
{
frame = Mp3Frame.LoadFromStream(readFullyStream, true);
}
catch (EndOfStreamException)
{
this.fullyDownloaded = true;
// reached the end of the MP3 file / stream
break;
}
catch (WebException)
{
// probably we have aborted download from the GUI thread
break;
}
if (decompressor == null)
{
// don't think these details matter too much - just help ACM select the right codec
// however, the buffered provider doesn't know what sample rate it is working at
// until we have a frame
WaveFormat waveFormat = new Mp3WaveFormat(frame.SampleRate, frame.ChannelMode == ChannelMode.Mono ? 1 : 2, frame.FrameLength, frame.BitRate);
decompressor = new AcmMp3FrameDecompressor(waveFormat);
this.bufferedWaveProvider = new BufferedWaveProvider(decompressor.OutputFormat);
this.bufferedWaveProvider.BufferDuration = TimeSpan.FromSeconds(20); // allow us to get well ahead of ourselves
//this.bufferedWaveProvider.BufferedDuration = 250;
}
int decompressed = decompressor.DecompressFrame(frame, buffer, 0);
//Debug.WriteLine(String.Format("Decompressed a frame {0}", decompressed));
bufferedWaveProvider.AddSamples(buffer, 0, decompressed);
}
} while (playbackState != StreamingPlaybackState.Stopped);
Debug.WriteLine("Exiting");
// was doing this in a finally block, but for some reason
// we are hanging on response stream .Dispose so never get there
decompressor.Dispose();
}
}
finally
{
if (decompressor != null)
{
decompressor.Dispose();
}
}
}
}

Answer 2

NAudio does not include an MP3 encoder. When I need to encode MP3 I use lame.exe. If you don't want to go via a file, lame.exe allows you to read from stdin and write to stdout, so if you redirect standard in and out on the process you can convert on the fly.