Xamarin.iOS audio streaming not working, events not being triggered - ios

Question

So, my problem is that I'm trying to stream audio on Xamarin.iOS with the AudioFileStream and OutputAudioQueue classes. I have added handlers for the PacketDecoded and PropertyFound events, but they are not being triggered. What's wrong? My code is below...
class AudioStreamer : IAudioStreamer // this is my dependency service interface
{
bool outputStarted;
AudioFileStream afs;
OutputAudioQueue oaq;
public void StartStreaming(string url)
{
afs = new AudioFileStream(AudioFileType.MP3);
// event handlers, these are never triggered
afs.PacketDecoded += OnPacketDecoded;
afs.PropertyFound += OnPropertyFound;
GetAudio(url);
}
void GetAudio(string url)
{
// HTTP
NSUrlSession session = NSUrlSession.FromConfiguration(
NSUrlSessionConfiguration.DefaultSessionConfiguration,
new SessionDelegate(afs),
NSOperationQueue.MainQueue);
var dataTask = session.CreateDataTask(new NSUrl(url));
dataTask.Resume();
}
// event handler - never executed
void OnPropertyFound(object sender, PropertyFoundEventArgs e)
{
if(e.Property == AudioFileStreamProperty.ReadyToProducePackets)
{
oaq = new OutputAudioQueue(afs.StreamBasicDescription);
oaq.BufferCompleted += OnBufferCompleted;
}
}
// another event handler never executed
void OnPacketDecoded(object sender, PacketReceivedEventArgs e)
{
IntPtr outBuffer;
oaq.AllocateBuffer(e.Bytes, out outBuffer);
AudioQueue.FillAudioData(outBuffer, 0, e.InputData, 0, e.Bytes);
oaq.EnqueueBuffer(outBuffer, e.Bytes, e.PacketDescriptions);
// start playing if not already
if(!outputStarted)
{
var status = oaq.Start();
if (status != AudioQueueStatus.Ok)
System.Diagnostics.Debug.WriteLine("Could not start audio queue");
outputStarted = true;
}
}
void OnBufferCompleted(object sender, BufferCompletedEventArgs e)
{
oaq.FreeBuffer(e.IntPtrBuffer);
}
}
// instantiated in GetAudio()
class SessionDelegate : NSUrlSessionDataDelegate
{
readonly AudioFileStream afs;
public SessionDelegate(AudioFileStream afs)
{
this.afs = afs;
}
// this is, too, never executed
public override void DidReceiveData(NSUrlSession session, NSUrlSessionDataTask dataTask, NSData data)
{
afs.ParseBytes((int)data.Length, data.Bytes, false);
}
}
Btw, I mostly copied the code from this screencast.

Answer 1

Your code looks correct...
1) I see the "http://" comment in your source. Are your streaming from a http:// source without adding an ATS exception? If so, the dataTask.Resume(); is a "silent code failure" and thus none of your delegates/events will be called, BUT iOS will log it.
Check output log for something like:
StreamingAudio[13602:591658] App Transport Security has blocked a cleartext HTTP (http://) resource load since it is insecure. Temporary exceptions can be configured via your app's Info.plist file.
Use https:// sources, but if you have to turn ATS off completely for testing:
<key>NSAppTransportSecurity</key>
<dict>
<key>NSAllowsArbitraryLoads</key><true/>
</dict>
Note: Search iOS ATS for more info or details in order to only allow non-secure http:// from the server(s) that you would be streaming from, but the iOS' future is https:// only so start preparing... ;-)
2) If the URL source provided to NSUrlSession produces a Connection refused, that is a silent failure, AND there is no logging about it and of course none of your delegates/events are called... Pre-test that your streaming web services are active, try using curl, wget, etc.. to test the stream...
3) I see your streaming MP3s, so you should be OK, but remember there are hundreds of variations to the format and iOS does not stream/play them all so try a different mp3 encoded via a different toolset just to double-check...